OIF-Co-Packaging-FD-01.

Co-Packaging Framework Document

OIF-Co-Packaging-FD-01.0

February 3, 2022

Implementation Agreement created and approved

OIF
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The OIF is an international non-profit organization with over 100 member companies, including the world’s
leading carriers and vendors. Being an industry group uniting representatives of the data and optical worlds,
OIF’s purpose is to accelerate the deployment of interoperable, cost-effective and robust optical internetworks
and their associated technologies. Optical internetworks are data networks composed of routers and data
switches interconnected by optical networking elements.
With the goal of promoting worldwide compatibility of optical internetworking products, the OIF actively
supports and extends the work of national and international standards bodies. Working relationships or formal
liaisons have been established with CFP-MSA, COBO, EA, ETSI NFV, IEEE 802.3, IETF, INCITS T11, ITU SG-15, MEF,
ONF.

For additional information contact:

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Working Group: Physical Link Layer Working Group

TITLE: Co-Packaging Framework Document

SOURCE: TECHNICAL EDITOR PLL WORKING GROUP CHAIR

Kenneth Jackson David R. Stauffer, Ph. D.
Sumitomo Electric Kandou Bus, S.A.
2355 Zanker Rd. QI-I
San Jose, CA 95131 1015 Lausanne Switzerland
Phone: +1-626-506-9975 Phone: +1 802 316 0808
Email: kjackson@sei-device.com Email: david@kandou.com

PLL WORKING GROUP – CO-PACKAGING VICE CHAIR

Jeff Hutchins
Ranovus
Phone: +1 408 627 8036
Email: jeff@ranvous.com

ABSTRACT: This Framework Document addresses the application spaces and relevant technology considerations
for co-packaging of optical and electrical communication interfaces with one or more ASICs. A primary objective of
this effort is to identify new opportunities for interoperability standards for possible future work in the OIF or
other standards organizations.
Notice: This Technical Document has been created by the Optical Internetworking Forum (OIF). This document is offered to the OIF
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rights to at any time to add, amend, or withdraw statements contained herein. Nothing in this document is in any way binding on the OIF or any
of its members.
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been or may be asserted by any third party, the validity of any patent rights related to any such claim, or the extent to which a license to use
any such rights may or may not be available or the terms hereof.
Copyright © 2021 Optical Internetworking Forum

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ANY IMPLIED WARRANTIES OF MERCHANTABILITY, TITLE OR FITNESS FOR A PARTICULAR PURPOSE.

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1 Table of Contents

COVER SHEET………………………………………………………………………….. 1
1 TABLE OF CONTENTS .............................................................................................. 4
2 LIST OF FIGURES ...................................................................................................... 6
3 LIST OF TABLES ........................................................................................................ 7
4 DOCUMENT REVISION HISTORY ............................................................................ 8
5 INTRODUCTION ......................................................................................................... 9
6 APPLICATIONS OVERVIEW ................................................................................... 11
7 POTENTIAL INTERFACES FOR INTEROPERABILITY STANDARDS ................ 14
7.1 Introduction .......................................................................................................................................14
7.2 Electrical Interfaces............................................................................................................................14
7.2.1 Electrical Footprint .....................................................................................................................17
7.2.2 Socket Retention Mechanism .....................................................................................................18
7.3 Optical Interfaces ...............................................................................................................................18
7.3.1 Light (Laser) Sources ...................................................................................................................18
7.3.2 Pigtailed and/or Connectorized ..................................................................................................21
7.3.3 Connector or Fiber Exit Location and Size ..................................................................................21
7.3.4 Optical Budget ............................................................................................................................21
7.4 Thermal ..............................................................................................................................................22
7.4.1 Cooling Systems for Co-Packaging ..............................................................................................22
7.4.2 Reported Thermal Data: .............................................................................................................25
7.5 Power .................................................................................................................................................25
7.5.1 Supply Voltages, Currents ...........................................................................................................25
7.6 Management Interface ......................................................................................................................25
7.6.1 CMIS Over 2-Wire, SPI ................................................................................................................25
7.7 Environmental....................................................................................................................................26
7.8 Reliability, Redundancy and Repairability .........................................................................................26
7.8.1 Infant Mortality Targets and Over-Life Targets ..........................................................................27
8 SUMMARY................................................................................................................. 28
9 REFERENCES .......................................................................................................... 28

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9.1 Informative References .....................................................................................................................28

10 APPENDIX A: GLOSSARY .................................................................................. 28
11 APPENDIX B: GENERALIZED LASER SAFETY FOR MPO-BASED ELS
MODULES ........................................................................................................................ 32
11.1 Introduction .....................................................................................................................................32
11.2 Laser Product Classification and Required Safety Features ............................................................32
11.3 Laser Class (IEC 60825-1) Versus Laser Hazard Levels (IEC 60825-2) ..............................................34
11.3.1 Measurement Geometry ..........................................................................................................35
11.4 OFCS Power Limits (IEC 60825-2: 2021) ..........................................................................................36
11.5 Accessible Emission Limit (AEL) Calculations, Wavelength (IEC 60825-1:2014 Laser Class 1/1M) .38
11.6 Exposure Level Versus Fiber Launch Power P0 At 1271 nm ............................................................40
11.7 AEL Calculations for MPO Connector – Condition 3: Aperture Distance 100 mm ..........................42
11.7.1 All Fibers Active.........................................................................................................................42
11.7.2 Two Groups of 4 Fibers Active ..................................................................................................43
11.7.3 Every Second Fiber Active.........................................................................................................44
11.7.4 Four Active Fibers with Maximum Separation .........................................................................45
11.8 AEL Calculations for MPO Connector – Condition 2: Aperture Distance 35 mm ............................46
11.8.1 All Fibers Active.........................................................................................................................46
11.9 Burn Hazard Labeling .......................................................................................................................47
11.10 AEL Calculations for Short Time Exposure (Laser class 1/1M) ......................................................47
11.11 Sample Scenarios for ELS Modules with Accessible MPO Connectors..........................................49
11.11.1 Eight Fibers at 18 dBm Each (Wavelengths 1271 nm, 1291 nm, 1311 nm, 1331 nm) ...........49
11.11.2 Eight Fibers at 22 dBm Each (Wavelengths 1271 nm, 1291 nm, 1311 nm, 1331 nm) ...........50
11.11.3 Four Fibers at 24 dBm Each (Wavelength 1311 nm Only)......................................................51
12 APPENDIX C: LIST OF COMPANIES BELONGING TO OIF WHEN
DOCUMENT IS APPROVED ........................................................................................... 52

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2 List of Figures
Figure 1: Co-Packaging implementation....................................................................................................... 9
Figure 2: Example use-cases for Co-Packaged optical or electrical engines. .............................................10
Figure 3: Applications potentially benefitting from co-packaging. ............................................................12
Figure 4: Possible common optical interconnect requirements for the indicated applications and
associated endpoints. ..................................................................................................................................13
Figure 5: Re-timed. Note: Trace length and SerDes type informational. Achievable distance depends
on channel impairments including insertion loss, crosstalk, package parasitics and impedance
discontinuities. .............................................................................................................................................15
Figure 6: Linear amplified. Note: Trace length and SerDes type informational. Achievable distance
depends on channel impairments including insertion loss, crosstalk, package parasitics and impedance
discontinuities. .............................................................................................................................................16
Figure 7: Half-retimed. Note: Trace length and SerDes type informational. Achievable distance
depends on channel impairments including insertion loss, crosstalk, package parasitics and impedance
discontinuities. .............................................................................................................................................16
Figure 8: Direct drive. Note: Trace length and SerDes type informational. Achievable distance depends
on channel impairments including insertion loss, crosstalk, package parasitics and impedance
discontinuities. .............................................................................................................................................17
Figure 9: Laser Light Sources: Use-cases, proposed terminology, and associated laser safety
considerations. Numbered figure at left corresponds to an external laser source implementation. .......19
Figure 10: Scenarios for optical power from ELS to OE. (a) 1:Na, (b) 1:Nb, (c) 1:Nc, (d) 1:1, (e) Ne:1, (f)
Nf:1.. ............................................................................................................................................................20
Figure 11: ELS interdependencies on other critical elements of the co-packaging ecosystem. ................21
Figure 12: Impact of mid-board optical connectors. ..................................................................................22
Figure 13: A typical 1RU data center Ethernet switch with 32 QSFP-DD 400Gb/s ports. ..........................23
Figure 14: Switch ASIC power consumption trends. ..................................................................................23
Figure 15: Generic reliability curve for co-packaging applications. ............................................................27

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3 List of Tables
Table 1: Required features for the applications considered. (Note: Grayed cells to be completed when
system requirements are better defined.) ...................................................................................................13
Table 2: Attributes for the applications communication’s links endpoints. ..............................................14
Table 3: Signaling formats and protocols for the specified applications. ..................................................14
Table 4: Tradeoffs between solder reflow and socket attach approaches for co-packaged engines. .......17
Table 5: Typical 1RU data center switch power consumption* ..................................................................23
Table 6: Possible system cooling approaches. ............................................................................................24
Table 7: Reliability targets. .........................................................................................................................27
Table 8: Laser product classification and required safety features for IEC/EN 60825-1 3rd edition. .........32
Table 9: Requirements Summary ...............................................................................................................33
Table 10: Summary of requirements for location types in OFCS (IEC 60825-2: 2021)...............................34
Table 11: Measurement aperture diameters and measurement distances for the default (simplified)
evaluation. ...................................................................................................................................................35
Table 12: OFCS power limits for 11 µm mode field diameter single-mode fiber and 0.1 numerical
aperture multimode fibers (core diameter 50 µm). ....................................................................................36

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4 Document Revision History

Working Group: Physical and Link Layer Working Group

SOURCE: TECHNICAL EDITOR PLL WORKING GROUP CHAIR

Kenneth Jackson David R. Stauffer, Ph.D.
Sumitomo Electric Kandou Bus, SA
2355 Zanker Rd. QI-I
San Jose, CA 95131 1015 Lausanne, Switzerland
Phone: +1-626-506-9975 Phone: +1-802-316-0808
Email: kjackson@sei-device.com Email: david@kandou.com

DATE: February 3, 2022

Document Date Revisions/Comments

Feb 03,
OIF-Co-Packaging-FD-01.0 Initial document release
2020

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5 Introduction
Next generation datacenter switching networks and high-performance computing, such as machine-
learning and artificial intelligence, are increasingly challenged by a combination of high-power
dissipation and the need for high bandwidth I/O escape from the ASICs enabling these applications.
Scaling of current architectures suggest that next generation systems will challenge the cooling
capabilities of these systems. New architectures and new technology implementations are required if
the desired performance levels are to be achieved.
Co-packaging, where optical or electrical communications devices are attached on the same first-level
substrate as the host ASIC (Figure 1), is expected to provide high bandwidth interconnects with
significant power savings. By locating the optical engine in close proximity to the Host ASIC, the high-
speed electrical channel losses and impedance discontinuities can be minimized, thus enabling the use
of higher speed, lower power, off-chip I/O drivers.

Figure 1: Co-Packaging implementation.

Figures 2a – d show some specific use-cases with different packaging arrangements for engines and
ASICs. The Co-Packaging Assembly (CPA) is a Multi-Chip Module (MCM) with either socketed or
soldered ASIC and Optical Engines (OE) or Electrical Engines (EE) placed onto a high-performance
substrate.

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Figure 2: Example use-cases for Co-Packaged optical or electrical engines.

Figure 2c shows a use case where the engine locations are populated with a passive Copper Cable
Assembly (CCA) to connect to close-proximity transceivers (such as coherent) which may not fit into the
OE or EE footprint for co-packaging. The CCA could also be used to connect with an on-board optical or
electrical engine, or with a front-panel module.
Figure 2d shows a use-case where a packaged ASIC (ASIC die plus ASIC substrate/RDL) and engine are
attached to a common substrate using sockets which facilitate the attachment and removal of the
devices during assembly and rework. This arrangement is referred to as socketed, “near-package
optics” (NPO).

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The purpose of this Framework Document is to identify some of the key applications and their
requirements for which co-packaging implementations may provide significant benefits. This paper will
also discuss some of the issues associated with optical and electrical co-packaging and identify
opportunities and develop industry consensus to pursue interoperability standards. It is expected that
this Framework project will result in follow-on standardization activities at the OIF or other appropriate
standard bodies.

6 Applications Overview
Three applications have been identified as benefitting from co-packaging (Figure 3):
1) Data center networking, which typically include Ethernet NICs and switches connecting servers
and storage devices,
2) AI training / machine learning, where specialized high-performance graphics or tensor
processors are tightly coupled to process (learn) from examples (training data) to provide
predictions and/or decisions and
3) System disaggregation, where the processing, memory and storage functions are shared among
multiple compute nodes to increase usage efficiency.

Each application contains two communications endpoints, a Switching Node, connected to another
Switch node or an End-node. They each have different requirements and operating environments.
These applications are expected to drive the need for even higher bandwidth interconnects with lower
latency and lower power dissipation than today’s implementations. Current approaches (those typically
employing pluggable optical transceivers or passive copper cables) will have difficulty meeting these
requirements and next generation systems require new architectures and technologies. By co-
packaging the communications interfaces (e.g., optical or electrical engines) in close proximity to the
ASIC, high data-throughput interconnects with lower power and lower latency are possible.

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Figure 3: Applications potentially benefitting from co-packaging.

These co-packaged applications may use a variety of electrical interface standards such as XSR, LR, PCIe,
or even wide interfaces such as AIB. Some of electrical interfaces will be low latency typically
implemented with no FEC or perhaps a very low latency FEC code.

Although these applications can have different overall requirements, the insertion loss of the optical
interconnects supporting these applications can be similar. Figure 4 shows co-packaged optical engines
with multiples of base lane data-rates of 100Gb/s and an optical insertion loss budget of 4dB (for single-
mode fiber-based implementations) for use in data center networking and AI Training with Ethernet
protocols. Short reach data center networking applications may have a loss budget of 1.8dB (for multi-
mode fiber-based implementations). For some of the AI Training and disaggregated systems, where the
resources being shared are not bandwidth intensive the base lane data-rate is expected to be lower
(e.g., 32Gb/s NRZ interfaces based on PCIe gen 5) together with a lower-latency protocol such as CXL.
Memory disaggregation, on the other hand, requires transfers of large data blocks between many
endpoints (memory) and processors. Large radix switches with low latency will be needed and all-
optical switching approaches may provide the desired performance. As a result, the optical insertion
loss budget increases from 4dB to 8-10dB to accommodate these kinds of implementations.

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Figure 4: Possible common optical interconnect requirements for the indicated applications and
associated endpoints.
Table 1 shows some other required features for these applications, including energy efficiency, type of
engine at the end node, number of engines per end node and switch node as well as engine reliability.
Cells without values are expected to be added when the requirements are better defined.
Table 1: Required features for the applications considered. (Note: Grayed cells to be completed when
system requirements are better defined.)
Application
Data Center
Switching Network Disaggregation
HPC / AI AI Training / ML Disaggregation
(including Short (Memory)
Reach)
Ethernet CXL
Increased
Point-to-point Point-to-point Point-to-point
Radix
Energy Efficiency 1 ≤ 15 pJ/b ≤ 15 pJ/b 5-10 pJ/b 5-10 pJ/b 5-10 pJ/b 5-10 pJ/b

Pluggable or CoPkg CoPkg CoPkg CoPkg CoPkg CoPkg

Engine End Node
4 x 106G 32 x 106G 32 x 106G 32 x 32G 32 x 32G 32 x 32G

Engines per End Node 1x 2x to 4x 4x to 8x 2x to 4x 2x to 4x

Engine per Switch Node 16x 16x
Switch Capacity ≤ 51.2T ≤ 51.2T
2
Engine Reliability 10 FIT (3.2T) 10 FIT (3.2T) 10 FIT (3.2T)
3
3.2Tb/s Laser Source Reliability 50 FIT (3.2T) 50 FIT (3.2T) 50 FIT (3.2T)
Engine and Laser Source Lifetime 6 years 6 years 6 years

1 Energy efficiency estimates include engine-side host electrical interface, CDR, PIC components, and laser source.
Excludes switch-side. Assumes XSR electrical interface for Ethernet co-packaged optics applications.
2 Contribution to reliability from an engine excluding contribution from lasers
3 Contribution to reliability from lasers excluding contribution from engine.

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Table 2 shows the attributes for the applications’ endpoints and Table 3 shows the expected signaling
formats and protocols for the different applications.
Table 2: Attributes for the applications communication’s links endpoints.
Location
Switch Node End Node
(Dense) (sparse)
High Speed
Electrical I/F High speed (density)
Wide
Air Cooling Air Cooling
Thermal
Liquid Cooling Liquid Cooling
Optical Higher Fiber Count Lower Fiber Count

Internal Internal
Lasers
External External
Optical Engine Co-packaged
Co-packaged
Form Factor Module

Table 3: Signaling formats and protocols for the specified applications.

Signaling
MAC Electrical Optical (Point-to-point) Increased Radix
4dB
- 100G-CWDM4-OCP
Ethernet - CEI-112G-XSR at 103 or 106 Gb/s per lane - 100G-PSM4
• 100GbE - CEI-112G-LR at 106 Gb/s per lane - 400GBASE-FR4/DR4 N/A
• 400GbE -CEI-224G (TBD) at up to 224 Gb/s per lane 1.8dB:
-100GBASE-VR/SR
400GBASE-VR4/SR4
CXL4 n x 4 x 32G NRZ 4dB CXL DR/FR 8-10dB CXL
• n x 32GT/s Wide I/F w/ optional FEC (potentially MMF solutions) xWDM/PSM

In the remainder of this document, the data center networking application will be the primary focus
describing possible co-packaging solutions for a 51.2Tb/s Ethernet switch in a 1RU configuration.

7 Potential Interfaces for Interoperability Standards

7.1 Introduction
In this section, the potential interfaces for interoperability standards, including electrical, optical, and
mechanical interfaces along with environmental operating conditions are described.
7.2 Electrical Interfaces
As mentioned earlier, co-packaging is expected to provide high bandwidth interconnects with significant
power savings. By locating these communications interfaces (engines) in close proximity to the ASICs,

4CXL is used here as an example of a short-range device interconnect providing high-bandwidth, low latency
connectivity. Other interconnect protocols with similar capabilities may be suitable.
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the high-speed electrical channel losses and impedance discontinuities can be minimized, thus enabling
the use of higher speed, lower-power, off-chip I/O drivers from the ASIC. Some of the electrical
interfaces being considered are described in Figure 5 through Figure 8. The “re-timed” interface shown
in Figure 5 is expected to utilize the CEI-112G-XSR-PAM4 Extra Short Reach Interface implementation
agreement currently being developed. The transmit (Tx) and receive (Rx) functions contained in the
host ASIC side of the interface will have sufficient capabilities (e.g., drive amplitude, equalization, etc.) to
enable low error rate communications between the ASIC and optical engine over approximately 50mm
of 1st level packaging substrate, including package parasitics from the ASIC and the optical engine
assembly. Test points, test methodologies and test criteria will be part of an IA associated with these
component interfaces in future projects.

Figure 5: Re-timed. Note: Trace length and SerDes type informational. Achievable distance depends
on channel impairments including insertion loss, crosstalk, package parasitics and impedance
discontinuities.

Figure 6 shows another potential electrical interface, “Linear Amplified”. In this case, the CDR/DSP
function in the engine is eliminated (to reduce power dissipation) but because the modulation format
may be PAM4, the drive signal must be relatively linear without amplitude compression. In addition, the
SerDes in the ASIC must compensate for the entire link, from SerDes Tx to SerDes Rx. As a result, the Tx
and Rx functions in the ASIC must have greater capability (e.g., more amplification and peaking) than

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similar functions in the “Re-Timed” interface shown in Figure 5.

Figure 6: Linear amplified. Note: Trace length and SerDes type informational. Achievable distance
depends on channel impairments including insertion loss, crosstalk, package parasitics and impedance
discontinuities.

Another interface option, shown in Figure 7, is referred to as “Half-retimed”. Here one-half (either Tx or
Rx) of the engine and ASIC communication is re-timed, with the other half utilizing a linear-amplified
approach. This approach combines implementations from Figure 5 and Figure 6.

Figure 7: Half-retimed. Note: Trace length and SerDes type informational. Achievable distance
depends on channel impairments including insertion loss, crosstalk, package parasitics and impedance
discontinuities.
The last host ASIC to engine interface considered is shown in Figure 8, “Direct Drive”. Here the engine
functionality is simplified leaving only those functions necessary to support a linear optical
communications channel (due to a PAM4 modulation format assumption). The host ASIC contains the
necessary capabilities to drive the optical signals (e.g., sufficient amplitude capabilities to drive the
optical modulator or laser) as well as equalization on the receive path to remove impairments imposed
by the optical and electrical signal paths and enable error-free communications. Trace lengths for this
approach are expected to be much shorter than the previous interfaces described due to the desire to
eliminate DSP/CDR and amplification functionality. Again, for this electrical interface, test points, test
methodologies and test criteria would be included in a future IA.

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Figure 8: Direct drive. Note: Trace length and SerDes type informational. Achievable distance
depends on channel impairments including insertion loss, crosstalk, package parasitics and impedance
discontinuities.
For some of the use-cases shown in Figures 2a-d, the XSR electrical interface specification may be
insufficient due to the increased channel loss and impedance discontinuities. In these cases, an
enhanced electrical interface specification may be required (e.g. CEI-112G-XSR+-PAM4), having greater
transmit voltage amplitude swings, and increased equalizer capabilities.
7.2.1 Electrical Footprint
The overall size of the co-packaged optical or electrical engine will be determined by the total
bandwidth capability of the engine, wiring density on the engine and CPA substrate, the physical size of
the optical fiber attachment interface and the thermal management approach. The engine is attached
to the CPA substrate using a soldered ball-grid or copper pillar array or an array type removable
connection (e.g., land-grid array). In the latter case, a retention mechanism is required which consumes
CPA substrate area and can limit the achievable density.
Some of the trade-offs between a solder reflow attach and socket attached are shown in Table 4.
Table 4: Tradeoffs between solder reflow and socket attach approaches for co-packaged engines.

Criteria Solder Reflow Socket

Configurability Requires Reflow compatible Mountable, expandable to non-
components. Enable Surface reflow application.
mount technology of optical
engine.
Electrical Performance / signal Can be close to optimal Can be excellent
integrity
Footprint Highest Density Requires Clamping/Retention
Mechanism
Rework Limited and Yield Loss Yes, but access limited in field
Large number of CPO engine / High count integration yield Complexity enabler
Complex System in Package loss
Thermal Conventional approaches attached with Retention hardware

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7.2.2 Socket Retention Mechanism

When the engine is socketed on the CPA, a mechanical compression mechanism is required to compress
the socket interposer and provide good electrical contact. The compression mechanism typically
involves using bolts in the four corners surrounding the socket. The socket overhead can be reduced by
ganging the socket compression hardware thereby sharing the bolt hardware and improving density.
7.3 Optical Interfaces
Like their pluggable counterparts, optical engines will provide connectivity between switches and
servers over single mode or multimode optical fiber. Optical engines that are compliant and
interoperable with pluggable module standards and work over installed cabling will have broader
market appeal. For Data Center Networking, relevant application standards found in IEEE Ethernet 802.3
include 400GBASE-DR4 (802.3bs) and 400GBASE-FR4 (802.3cu). Short Reach Data Center Networking
may use emerging standards like 400GBASE-SR4 and 400GBASE-VR4 (802.3db) to enable low cost and
low power optical links.
7.3.1 Light (Laser) Sources
Choosing the optimal laser source is critical to designing a co-packaged optics switch. The optical source
may consist of multiple lasers operating at multiple wavelengths (to support FR applications) or a single
laser or multiple lasers operating at a single wavelength (to support DR, VR and SR applications). When
the optical engine is implemented using silicon photonic technology, the lasers maybe integrated within
the engine or located externally as shown in Figure 9. In the external laser case, a high output power
continuous wave (cw) optical source is used in conjunction with the modulators to provide a modulated
data-stream.
External laser sources (ELS) can improve the reliability of a CPO switch because lasers that have failed
may be swapped at the faceplate without removing the switch from operation. In addition, ELS
architectures physically separate the switch ASIC from the laser which improves the thermal
environment for both. These benefits come at the cost of higher insertion loss. These losses must be
compensated by increasing the output power of the ELS. Integrated lasers inside the optical engine have
fewer losses to overcome and may operate at lower optical power. VCSEL based optical engines with
multimode fibers have the potential to be the lowest cost and lowest power option for co-packaged
optics for short reach applications.

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Figure 9: Laser Light Sources: Use-cases, proposed terminology, and associated laser safety
considerations. Numbered figure at left corresponds to an external laser source implementation.
When considering an external light source, a single form-factor may contain many lasers. Each laser
may supply light to a single or to multiple modulators in the silicon photonic engine. Figure 10 shows
various optical power delivery scenarios. For cases where the laser power is high, power splitting can be
either inside the ELS, inside the OE, or between the ELS and OE. For cases where the laser power is low
or multiple frequencies are needed, power combining can be inside the ELS or inside the OE.
Additionally, there are cases where each laser feeds a single lane of the OE transmitter directly.

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Figure 10: Scenarios for optical power from ELS to OE. (a) 1:Na, (b) 1:Nb, (c) 1:Nc, (d) 1:1, (e) Ne:1, (f)
Nf:1..
Future efforts to standardize ELS modules such as an Implementation Agreement in the OIF or an MSA
must coordinate the activity with other critical elements of the co-packaging ecosystem. Figure 11
shows the various interdependencies.
Finally, ELSs must be compliant with relevant laser eye safety standards (e.g., IEC 60825-1 2014 (3rd ed)
and IEC 60825-2 2021 (ed 4.0)) (see Appendix B: Generalized Laser Safety for MPO-Based ELS Modules).
Typically, this means no firmware in the safety system. It should be hardwired, with typically
microsecond assertion timings. The approach implemented needs to ensure that mis-connected
scenarios are detectable and that the ELS be held at eye safe limit until the optical engine confirms
connection integrity. The engine may need to feedback information to the ELS when no light is detected
causing the light source to shut down.

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Figure 11: ELS interdependencies on other critical elements of the co-packaging ecosystem.
7.3.2 Pigtailed and/or Connectorized
The engine can be either assembled with pigtail or built-in connector to carry the high-speed data in and
out of the engine. The pigtail can consist of a ribbon fiber for high density optical interfaces, or a copper
cable assembly for high density electrical interfaces.
By definition, a connectorized engine will require an extra connector to reach the front panel. The
pigtailed option may not require an extra connector if the pigtail is long enough to reach the front panel.
The addition of an extra connector increases the insertion loss over an equivalent front-panel pluggable
transceiver. The existing high density fiber optic connectors (e.g., MPO) do not meet the size and
density constraints and may require a new connector technology to be developed.
7.3.3 Connector or Fiber Exit Location and Size
The fiber or copper cable exit away from the co-packaged assembly (CPA). Copper cables and surface
coupled optical engines may need additional height above the socket to accommodate the attachment
scheme. The additional height needs to be considered when designing the heat-sink approach.
7.3.4 Optical Budget
Optical specifications for front-panel pluggable modules are typically defined at TP2 and TP3 as shown in
Figure 12. The third option, “CPO Pigtail + jumper”, shows the inclusion of a mid-board optical
connector which increases the overall optical budget. Mid-board optical connectors enable the use of
only one pigtail length for each CPO module. They also can minimize damage from handling of the CPO
pigtail and if needed facilitates rework of failing optical connectors and components.
On the transmit side, the additional loss can be remedied by increasing the transmit power, likely by
increasing the laser power to meet the specifications at TP2. On the receive side, the additional loss is
likely compensated for by requiring better received sensitivity either by an improved receiver or by
reduced sensitivity margin in the receiver.

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Given the impact of faceplate connector loss on the optical loss budget, it is essential to control the
insertion loss of the connectors. A 51.2T switch will have 256-1024 fibers on the front panel. Standards
compliant connectors may have a loss distribution with a “long tail” that will be present when utilizing
many connectors. CPO switch integrators should use front panel optical connectors with better loss
performance characteristics than standards. In the industry these connectors are often called “Ultra Low
Loss” connectors and have maximum loss values of 0.35 dB for single mode and 0.2 dB for multimode at
beginning of life.

Figure 12: Impact of mid-board optical connectors.

Another key characteristic of the mid-board connector is that it is behind the front-panel such that it is
likely mated and then not tested until the entire assembly is completed and ready for test. As a result,
this “single-mate” scenario will likely require additional loss allocation compared to a typical optical
connector for which there is easy access to clean and remate the connector if the insertion loss is high.
Dense optical systems will be built with components different than what is used in conventional front-
panel pluggables. These dense optical technologies often have increased loss compared with
conventional approaches. In addition, end-users often require interoperability with existing
infrastructure employing conventional technologies. The combination of these two factors provides a
significant challenge for dense optical engines.
However, in the case where interoperability is not required (book-ended applications), the optical
budget can be optimized around the dense optical engine technology.
7.4 Thermal
7.4.1 Cooling Systems for Co-Packaging
Co-packaged engines will require some sort of thermal management, either a conduction path to
remove heat or to isolate the engine from other heat-generating components. In either case, the
thermal management approach will have to be compatible with the overall system cooling
implementation. Figure 13 shows a typical 1RU, data center switch in use today. The aggregate

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bandwidth is 12.8Tb/s and contains 32 pluggable optical transceiver ports. These switches are typically
cooled by fans that pull air in over the front-panel and exhaust through the rear.

Figure 13: A typical 1RU data center Ethernet switch with 32 QSFP-DD 400Gb/s ports.

Table 5 shows typical power dissipation values for some of the key functional blocks.
Table 5: Typical 1RU data center switch power consumption*

12.8 Tb/s NPU power consumption: 432 W

32 400G QSFP56-DD ports @ 12 W each 384 W
Typical power consumption (including fans, power
900W
suppliers, and typical power dissipation optics)
Total power consumption (worst case, maximum traffic,
1500 W
highest ambient temp & fan speed)
Ambient Operating temperature 0 to + 45 ⁰C
Redundant, hot swappable fans 7

* Operates with forward and reverse air flow

Figure 14: Switch ASIC power consumption trends.

In the near future, as network switching bandwidth increases, power consumption will increase (Figure
14) and forced air cooling approaches may be insufficient. Future network switches will likely require
alternative system cooling implementations. A comparison of the different system cooling approaches
is described in Table 6.

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Table 6: Possible system cooling approaches.

Cooling Approach Pros Cons

Well-known, well understood Limited cooling efficiency
technology
high reliability with multiple Acoustics (noise)
Air-Cooled hot-swappable fan arrays
widely used in data centers
low-cost
Improved cooling capacity limited (?) data-center deployments
compared to air-cooling
Liquid Cooling -- Closed loop quieter than all-air cooling Reliability mechanical pump)
No external plumbing more costly than air-cooling
needed
Improved cooling capacity Not widely deployed in data centers
compared to closed loop
liquid cooling
reliability local) is higher than requires external source of flowing
closed loop cooling -- no liquid and heat exchanger
Liquid Cooling -- Open loop pump
Reliability--failure of external source
can take down many units
Costs (heat exchange module, chilled
liquid network facility)
Improved cooling capacity Not widely deployed in data centers
compared to open/closed (requires external source of flowing
loop liquid cooling liquid and heat exchanger
Potentially highest Reliability (fluid contamination, pump
equipment density system)
Immersive Cooling
Optics and fiber connectors need to be
hermetic
Requires major re-architecting of
equipment
Costs-- not deployed in volume

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7.4.2 Reported Thermal Data:

Component temperatures or thermal margins are required by component and system designers as well
as operators to assess operational status. Typically, the laser case/base temperature is monitored for
this purpose as it reflects the status of the laser’s internal temperature control system. Co-packaged
Optical systems integrate lasers systems with signal processing ASICS, and other photonics elements.
These elements can have variable heat dissipation depending on operating mode, and FEC
requirements. These power changes mean the temperature difference between the case and junction
will vary for the same physical design. Consequently, a single case temperature may not be sufficient for
monitoring system purposes as other devices approach operating limits with only a small variation in
case temperature.
Although local case temperatures can reflect changes in overall internal power dissipation, the
operational status of DSP’s, drivers etc. will be better represented by the junction temperature sensors
of these devices. It is recommended that the CPO reports laser case/base temperature and identifies its
monitor location in addition to reporting at least one other temperature or thermal margin value that
reflects the junction temperature of any DSP or other photonics element.
7.5 Power
As seen in Table 1, the estimated energy efficiency for co-packaged dense optical engines is expected to
range from 5pJ/bit to 15pJ/bit depending on the particular application and CPO generation. For
example, a 3.2T optical engine with a 10pJ/bit energy efficiency will consume 32W. A 3.2T optical
engine footprint may be on the order of 20x20 mm2. Such a large power in a small area result in a
power density of 8W/cm2 which is much higher than what the optical industry is accustomed to.

7.5.1 Supply Voltages, Currents

Different implementations will be architected employing differing technologies and different IC nodes
resulting a variety of supply voltages and current draws for the supplies. For instance, an engine may
include an advanced CMOS ASIC and a microcontroller (µC) which typically have supply voltages well
below 1.0 volt. The engine may also need a supply to drive the high-speed I/O and perhaps higher
voltages for some of the optical components.
It is assumed the power supply conversion will be external to the engine as the power supply
components will probably add to the engine size and height. Therefore, the host will need to supply the
CPA with the necessary power supplies.
Even if the industry agrees to a common set of supplies, the required current draw per supply will vary
depending on the implementation.
The number of supplies and the max current draw will drive the number of power related contacts for
the engine as the current/contact guidelines are considered for the socket.
7.6 Management Interface
7.6.1 CMIS Over 2-Wire, SPI
Typically, pluggable modules serve one or two ports, however, dense optical engines will serve many
more ports. As an example, I2C was specified as a 2-wire management interface in the CMIS by the
QSFP-DD MSA. In a high-density co-packaging application, the same MIS interface will need to serve
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many more ports. Switching to a faster MIS I/F such as SPI would improve the time for servicing the
engines.
7.7 Environmental
The applications discussed in Section 6 are typically found in indoor, data center environments as
opposed to outdoor environments. Operating temperature ranges are typically in the range of room
temperature or higher than room temperatures and in next generation, much higher than room
temperature due to the power dissipation of these high-performance systems. Some typical high-level
operating conditions for a data center include the following:
• Altitude: 0 – 1800 meters (could include derating provisions)
• Relative Humidity (RH): 90 % max
• Ambient Temperature: 15 – 35 C
For co-packaging implementations more in-depth discussion and analysis will be needed to determine
the operating case temperatures or internal temperatures and which kind of thermal management
solution is employed (see Section 7.4.1).
7.8 Reliability, Redundancy and Repairability
The use of co-packaged engines is by nature less field serviceable than front panel pluggable designs.
As a result, there is a need for a reliability framework at both component and system level to align with
the target application requirements. For data center switch network fabrics, redundant links are
utilized to achieve acceptable performance even under fault conditions. Applications involving AI and
Machine Learning are typically less tolerant of a link failure due to higher aggregate bandwidth
requirements and a greater level of connectivity for acceptable cluster performance.
A generic reliability curve is shown in Figure 15. The goal is to establish solid fabrication, processing, and
assembly approaches with effective defect screens to minimize infant mortality. Component failure
rates must be established that are compatible and consistent with system failure rate targets for
random failures. In addition, it’s expected that adequate instrumentation and monitoring functions will
be implemented to enable pre-emptive service or replacement due to wear-out.

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Figure 15: Generic reliability curve for co-packaging applications.

7.8.1 Infant Mortality Targets and Over-Life Targets
Current pluggable transceiver module failure rates (~ 300 FIT) are insufficient if simply scaled for CPO
applications. End system reliability must be achieved by leveraging integration. Table 7 shows the
reliability targets for a data center network switch having an aggregate bandwidth of 51.2Tb/s
implemented with sixteen 3.2Tb/s co-packaged engines.
Table 7: Reliability targets.

Service Life
N AFR5 MTBF5 (hours) FIT
(years)
CPO Engine6 16 0.01% 100M 10 6
3.2Tb/s Laser Source7 16 0.04% 20M 50 6
Rest of System 1 (Sum) 0.09% 10M 100 6
Total System <1% <1146 6

Further study is required to confirm the reliability of CPO implementations. Redundancy at component
or sub-system level may be required to achieve overall system reliability targets. Furthermore, some
implementations with reduced data-throughput performance, e.g., lane reduction of multi-lane
interconnects, maybe required to enhance overall system availability.

5 AFR = Annualized Failure Rate (% per year), MTBF=Mean-Time-Between-Failures

6 Contribution to reliability from an engine excluding contribution from lasers
7 Contribution to reliability from lasers excluding contribution from engine.

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8 Summary
This Framework Document has addressed some of the key application spaces and relevant technology
considerations for co-packaging of optical and electrical communication interfaces with one or more
ASICs. Several optical and electrical interfaces as well as mechanical & thermal approaches have been
presented which could benefit from a standardization process, e.g., an Implementation Agreement in
the OIF. There are still other technology details and implementation aspects missing from this
document that will warrant further study and may lead to additional standardization efforts.

9 References
9.1 Informative References
• IEEE Standard for Ethernet--Amendment 10: Media Access Control Parameters, Physical Layers,
and Management Parameters for 200 Gb/s and 400 Gb/s Operation
• IEEE Standard for Ethernet--Amendment 11: Physical Layers and Management Parameters for
100 Gb/s and 400 Gb/s Operation over Single-Mode Fiber at 100 Gb/s per Wavelength
• IEEE 802.3ck (in-process)
• CEI-112G-XSR-PAM4 (in-process)
• IEC 60825-1: 2014 Safety of laser products – Part 1: Equipment classification and requirements
• IEC 60825-2: 2021 Safety of laser products – Part 2: Safety of optical fibre communication
systems (OFCS)

10 Appendix A: Glossary
AGC: Automatic gain control. Refers to the adjustment of the gain to enhance the dynamic range of the
amplifier.
AI: Artificial Intelligence.
AIB: Advanced Interface Bus. A chip-to-chip communications interface.
ASIC: Application specific integrated circuit.
CCA: Copper Cable Assembly
CDR: Clock and data recovery.
CMIS: Common Management Interface Specification. Refers to an industry specification which
implements I2C, two-wire serial interface for monitoring and control of various elements of co-
packaging.
CMOS: Complimentary Metal-Oxide-Semiconductor. A common silicon ASIC fabrication process.
Co-Packaged Assembly Socket: A co-packaged assembly attached to the host board with a removable
interface.
Co-Packaged Assembly Substrate: The substrate containing the ASIC and co-packaged engine.
CPA: Co-Packaged Assembly. ASIC plus engine (optical or electrical)
CPO: Co-Packaged Optics. Active optical components attached to a common substrate containing
ASICs.

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CTLE: Continuous time linear equalizer. Sometimes this is referred to as a “peaking” circuit where the
rising or falling edges have overshoot.
CXL: Compute Express Link is an open industry standard interconnect offering high-bandwidth, low
latency connectivity between host processor and devices such as accelerators, memory buffers, and
smart I/O devices.
DSP: Digital Signal Processor.
EIC: Electrical Integrated Circuit. Refers to the electrical portion of an optical engine---may contain
driver electronics to drive a laser or optical modulator as well as a transimpedance amplifier and post
amplifier to convert a photo-current (arising from the photodetector) into a usable electrical signal.
ELS: External Light Source. A high-power cw optical laser source providing light for the modulator
portions of an optical engine. It is located outside the boundary of the optical engine and therefore is
likely to experience a different set of environmental conditions.
FEC: Forward Error Correction.
FIT: Failures in Time (1e9 hours).
Front Panel (Faceplate): The user accessible boundary of the system which in this document refers to
the panel of a “19-inch rack”.
I/O: Input/Output driver. The output driver on the switch or processor host ASIC.
IA: Implementation Agreements, OIF documents that specify various names their defined interface
specifications.
Integrated Light Source: A high-power cw optical laser source providing light for the modulator portions
of an optical engine. It is bonded to the optical engine and typically launches light into the photonic
engine waveguides via evanescent coupling.
LD-DRV: Laser diode driver. Refers to the ASIC which drives the laser or more generally, the
optoelectronic device, which effectively acts as an electrical-to-optical converter.
MCM: Multi-Chip Module.
MMF: Multi-Mode Fiber. Optical fiber that transmits multiple spatial modes. Core diameters are much
larger than the wavelength of the light being transmitted, e.g., 50 µm.
MPO: Multiple-fiber Push-On/Pull-off. An optical fiber connector that can support multiple fiber
connections.
MR: Medium reach. Refers to the on-going project in OIF, CEI-112G-MR-PAM4, which is an electrical
interface specification for package substrate distances of approximately 500mm, or 20 dB channel loss
at the Nyquist frequency of the baud rate.
NIC: Network Interface Card.
NPU: Network Processing Unit. For example, a data center switch contained in a 1 RU chassis.
NRZ: Non return to zero, a binary code in which 1s are represented by one significant condition (usually
a positive voltage or presence of light) and 0s are represented by some other significant condition
(usually a negative voltage or absence of light), with no other neutral or rest condition.

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OIC/PIC: Optical Integrate Circuit/Photonic Integrated Circuit. Typically refers to the optical portion of
an optical engine---may contain waveguides, splitters, combiners, modulators as well as photodetectors.
On-chip Light Source: A high-power cw optical laser source providing light for the modulator portions of
an optical engine. It is attached to the optical engine and typically uses an imaging element (e.g., lens,
turning mirror) to couple light into the optical waveguides of the optical engine. Since the light source is
on-chip, the temperature range of operation is similar to that experienced by the photonic engine.
Optical Chiplet (Optical Engine (OE), Optical Tile, CPO Module): The active optical element converting
electrical signals from an ASIC to optical ones and vice-a-versa.
Optical/Electrical Engine (EE) Socket: An optical or electrical engine attached to the co-packaged
assembly substrate with a removable interface.
Optical/Electrical Engine Substrate: The substrate on which the optical or electrical engine is attached
to.
PAMx: Pulse-amplitude modulation is a form of signal modulation where the message information is
encoded in the amplitude of a series of signal pulses. For optical links it refers to intensity modulation.
As an example, PAM4 is a two-bit modulation that will take two bits at a time and map the signal
amplitude to one of four possible levels.
PCIe: Peripheral Component Interconnect Express.
PIC: Photonic Integrated Circuit.
Pluggable Optics: Optical transceivers that are inserted into the front-panel of a system rack and
provide the end-user with a variety of connection types. Some example form-factors include SFP, QSFP,
QSFP-DD, and OSFP)
PSMx: Parallel Single-Mode. An optical interface specification that uses “x” parallel single mode fibers
to transmit/receive optical signals. PSM4 is the terminology used to describe a 100Gb/s link using 4
pairs of single mode fibers with 25Gb/s per fiber.
QSFP-DD: Quad-Small Form-Factor Pluggable Double-Density. A transceiver form-factor with 8
electrical interface lanes in both directions capable of supporting up to 56Gb/s data rates per lane, for
an aggregate data-rate of 400Gb/s in either direction.
RDL: Redistribution Layer.
ROSA: Receiver Optical Sub-Assembly. Refers to the photodetector and frequently the transimpedance
amplifier within a package which usually provides a mechanism to align and couple the optical signal
contained in the incoming fiber to the photodetector.
RU: Rack Unit. A unit of measure frequently used as a measurement of the overall height of 19-inch
rack frames, as well as the height of equipment that mounts in these frames. The height of the frame or
equipment is expressed as multiples of rack units, e.g., 1RU, 2RU, 3RU, etc.
SerDes: Serializer/Deserializer.
SPI: Serial Peripheral Interface.
TIA: Transimpedance amplifier. A photodetector is connected to this electronic device which converts
the photo-current from the photodetector into a voltage.

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TOSA: Transmitter Optical Sub-Assembly. Refers to the laser and package which usually provides a
mechanism to align and couple the output of the laser to an optical fiber.
TPx: Test Points, TP2, TP3 as defined in IEEE.
VCSEL: Vertical Cavity Surface Emitting Laser. A type of laser, which for optical communications
applications, uses wavelengths in the range of 850 nm with multi-mode optical fibers.
WDM: Wavelength Division Multiplexing. An optical communications technology which combines
(multiplexes) several optical carrier signals of different wavelengths onto a single optical fiber.
XSR: Extra short reach. Refers to an on-going project in the OIF, CEI-112G-XSR-PAM4, which is an
electrical interface specification for package substrate distances of approximately 50mm, or 10 dB
channel loss at the Nyquist frequency of the baud rate.

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11 Appendix B: Generalized Laser Safety for MPO-Based ELS Modules

11.1 Introduction
This appendix explains the requirements for laser product classification, laser hazard levels, according to
the IEC standards IEC60825-1 and IEC60825-2. For ELS modules covered by this framework document,
those that have accessible MPO connectors, i.e., scenarios 2b and 3 in Figure 9, are analyzed in the
following subsections. Calculations are provided for several foreseeable configurations of fibers in MPO
connectors carrying various proposed power levels per fiber and at wavelengths suitable for -FR4 and/or
-DR4 interfaces.
11.2 Laser Product Classification and Required Safety Features
Table 8: Laser product classification and required safety features for IEC/EN 60825-1 3rd edition.
Laser Class
(IEC/EN 60825-1 3rd Ed) FDA Class Hazard Description
1 Class I Safe under reasonably foreseeable conditions
1M No equivalent As for Class 1 except may be hazardous if user employs optics
1C No equivalent See documentation
2 Class II Low power; eye protection normally afforded by aversion & active responses
2M No equivalent As for Class 2 except may be more hazardous if user employs optics
3R Class IIIa Direct intrabeam viewing may be hazardous
3B Class IIIb Direct intrabeam viewing normally hazardous
4 Class IV High power; diffuse reflections may be hazardous

Per ANSI:
“…In any case there shall be a designated LSO for all circumstances of
operation, maintenance, and service of a Class 3B or Class 4 laser or
laser system…”

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Table 9: Requirements Summary

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11.3 Laser Class (IEC 60825-1) Versus Laser Hazard Levels (IEC 60825-2)
The laser eye safety levels for IEC 60825-1 (Table 1) and for IEC 60825-2 (Table 10) are different.
Table 10: Summary of requirements for location types in OFCS (IEC 60825-2: 2021)

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11.3.1 Measurement Geometry

Table 11: Measurement aperture diameters and measurement distances for the default (simplified)
evaluation.

Condition 1 Condition 2 Condition 3

Applied to collimated beam where Applicable to optical fiber Applied to determine irradiation relevant for the
e.g. telescope or binoculars may communications systems, unaided eye, for low power magnifiers and
increase the hazarda see IEC 60825-2 scanning beams
Wavelength Aperture Stop Distance Aperture Stop / Distance
(nm) (mm) (mm) Limiting aperture (mm)
(mm)
< 302.5 - - 1 0
≥ 302.5 to 400 7 2,000 1 100
≥ 400 to 1,400 50 2,000 See Note 1 under 5.4.1 7 100
1 for t ≤ 0.35 s
≥ 1,400 to 4,000 7 x Condition 3 2,000 See Note 1 under 5.4.1 1.5 t3/8 for 0.35s < t < 10 s 100
3.5 for t ≥ 10 s
1 for t ≤ 0.35 s
≥ 4,000 to 105 - - 1.5 t3/8 for 0.35s < t < 10 s 0
3.5 for t ≥ 10 s
≥ 105 to 106 - - 11 0
NOTE: The descriptions below the “Condition” headings are typical cases for information only and not intended to be exclusive.
a Condition 1 is not applied for classification of laser products intended for use exclusively indoors and where intrabeam with telescopic optics

such as binocular telescopes is not reasonably foreseeable.

Two measurement conditions are specified for the determination of the accessible emission. Condition 1
is applied for wavelengths where aided viewing of collimated beams with telescopic optics may increase
the hazard. Condition 3 applies to the unaided eye. For power and energy measurement of scanned
laser radiation, only Condition 3 shall be used. For classification of laser products intended for use
exclusively indoors and where intra-beam viewing with telescopic optics such as binoculars is not
reasonably foreseeable, it is not required to apply Condition 1.
NOTE 1: Measurement Condition 3 also includes an evaluation of the radiation accessible for viewing
with a low power magnifying glass. Viewing with higher power magnifying optics as might occur with
fiber optic systems is covered in IEC 60825-2.

Limitations of the classification scheme are discussed in Clause C.3, suggesting cases where additional
risk analysis and warnings might be appropriate. Condition 2 was used in previous editions of this Part 1
as the "magnifying glass" condition.
The most restrictive of the applicable measurement conditions shall be applied. If the most restrictive
condition is not obvious, both conditions shall be evaluated. For Classes 1M or 2M, both conditions
always need to be evaluated.

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11.4 OFCS Power Limits (IEC 60825-2: 2021)

Table 12: OFCS power limits for 11 µm mode field diameter single-mode fiber and 0.1 numerical
aperture multimode fibers (core diameter 50 µm).
Wavelength Hazard Level
and Fiber Type 1 1M 2 2M 3R 3B
1.95 mW 3.77 mW 5.00 mW 9.66 mW 25.0 mW 500 mW
633 nm (MM)
(+2.9 dBm) (+5.8 dBm) (+7.0 dBm) (+9.9 dBm) (+14.0 dBm) (+27.0 dBm)
2.82 mW 5.45 mW 14.5 mW 500 mW
780 nm (MM) - -
(+4.5 dBm) (+7.4 dBm) (+11.6 dBm) (+27.0 dBm)
3.89 mW 7.52 mW 20.0 mW 500 mW
850 nm (MM) - -
(+5.9 dBm) (+8.8 dBm) (+13.0 dBm) (+27.0 dBm)
7.08 mW 13.7 mW 36.3 mW 500 mW
980 nm (MM) - -
(+8.5. dBm) (+11.4 dBm) (+15.6 dBm) (+27.0 dBm)
1.80 mW 2.66 mW 9.21 mW 500 mW
980 nm (SM) - -
(+2.5 dBm) (+4.2 dBm) (+9.6 dBm) (+27.0 dBm)
140 mW 270 mW 500 mW 500 mW
1270 nm (MM) - -
(+21.4 dBm) (+24.3 dBm) (+27.0 dBm) (+27.0 dBm)
46.2 mW 76.5 mW 237 mW 500 mW
1270 nm (SM) - -
(+16.6 dBm) (+18.8 dBm) (+23.7 dBm) (+27.0 dBm)
481 mW 500 mW 500 mW 500 mW
1310 nm (MM) - -
(+26.8 dBm) (+27.0 dBm) (+27.0 dBm) (+27.0 dBm)
166 mW 277 mW 500 mW 500 mW
1310 nm (SM) - -
(+22.2 dBm) (+24.4 dBm) (+27.0 dBm) (+27.0 dBm)
1400 nm to 1600 13.3 mW 371 mW 500 mW
- - See note to 3.9
nm (MM) (+11.2 dBm) (+25.7 dBm) (+27.0 dBm)
10.1 mW 115 mW 500 mW
1420 nm (SM) - - See note to 3.9
(+10.0 dBm) (+20.6 dBm) (+27.0 dBm)
10.2 mW 136 mW 500 mW
1550 nm (SM) - - See note to 3.9
(+10.1 dBm) (+21.3 dBm) (+27.0 dBm)
NOTE 1: Hazard levels 1M and 2M
The maximum power shown in the table for 11 µm fiber is limited by the power density. The precise fiber power limit is therefore
determined by the minimum expected beam divergence, which is in turn dependent on the MFD of a single-mode fiber. This can change for
different values of the MFD and there are significant changes in Class limits as the MFD changes. Some connectors use enlarg ed MFD
and the far field divergence is lower. These connectors can result in a higher hazard level and the higher hazard level is assigned when
using these connectors.
NOTE 2: Wavelength 1270 nm
Wavelength 1270 nm corresponds to the shortest wavelength in the datacom applications, e.g., LAN-WDM.
NOTE 3: Fiber parameters
The fiber parameters used are the most conservative cases; single-mode figures are calculated for a fiber with an 11 µm MFD, and
multimode figures for a fiber with a numerical aperture of 0.18. Many systems operating at 980 nm and 1550 nm use fibers with smaller
MFDs. For example, the limit for hazard level 1M when a wavelength of 150 nm is transmitted along dispersion shifted fiber cables having
upper limit values of MFD of 9.1 µm is 197 mW.

The maximum mean power within the fiber for each hazard level for the most important wavelengths
and optical fiber types used in OFCS is presented in Table 12. The values shown assume that APR is not
in operation. For most typical systems with duty cycles between 10 % and 100 %, the peak power can be
allowed to increase with duty cycle in an inversely proportional manner. However, for duty cycles ≤ 50
%, it is most straightforward to limit the peak powers to twice these mean power limits, although IEC
60825-1 can be used for a more sophisticated analysis to identify any increase in peak powers
permissible for these types of systems. This is especially valid when "visible sources" with wavelengths
in the photochemical hazard area are used.

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For the most common single-mode fibers, the point source limits need to be applied while for graded
index multimode fibers with a core diameter of 62.5 μm (GI 62.5), the effect of angular subtense, which
is linked to C6, needs to be considered for wavelengths between 400 nm and 1 400 nm.
The following aperture diameter and measurement distances are to be used for Condition 2
measurements:
 3.5 mm at 35 mm for wavelengths ≥ 302.5 nm and < 1,400 nm.
 3.5 mm at 14 mm for wavelengths ≥ 1,400 nm and < 4,000 nm.

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11.5 Accessible Emission Limit (AEL) Calculations, Wavelength (IEC 60825-1:2014 Laser Class
1/1M)

AEL Calculations
Wavelength [nm]: 1250-1350nm
Point Source (single fiber)

α ≤ 1.5 mrad: AEL = 3.9 * 10-4 C4 C7 W

C4 = 5
C7 = 8 + 100.04(λ –1 250)
t = 100 s
P0 based on Condition 3 (100 mm, 9.6 µm)

Wavelength AEL P0 P0
[nm] [mW] [mW] [dBm]
1271 29.09 99.73 19.99

1291 100.72 345.30 25.38

1311 500.00 500.00 26.99

1331 500.00 500.00 26.99

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11.6 Exposure Level Versus Fiber Launch Power P0 At 1271 nm

Where

Standard Single Mode Fiber SMF28e+

-4
PAEL = 3.9 * 10 C4 C7 W

C4 = 5
0.04(λ –1 250)
C7 = 8 + 10
t = 100s
ω0 = 9.6µm

λ = 1271nm

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11.7 AEL Calculations for MPO Connector – Condition 3: Aperture Distance 100 mm
11.7.1 All Fibers Active

AEL Calculations
Point Source (single fiber)
α ≤ 1.5 mrad: AEL = 3.9 * 10-4 C4 C7 W
Extended Source (multiple fibers)
α > 1.5 mrad: AEL = 3.5 * 10-3 C6 C7 T2-0.25 W
C4 = 5
C7 = 8 + 100.04(λ –1 250)
C6 = α/αmin
T2 = 10 * 10 [(α-αmin)/98.5] s
t = 100s

Wavelength [nm]: 1271 nm

Fiber Spacing [µm]: 250 µm
Fiber Diameter (MFD) [µm]: 9.6 µm

For Laser Class 1/Hazard Level 1M evaluations of MPO connectors two neighboring emitters present the
worst-case configuration.

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11.7.2 Two Groups of 4 Fibers Active

AEL Calculations
Point Source (single fiber)
α ≤ 1.5 mrad: AEL = 3.9 * 10-4 C4 C7 W
Extended Source (multiple fibers)
α > 1.5 mrad: AEL = 3.5 * 10-3 C6 C7 T2-0.25 W
C4 = 5
C7 = 8 + 100.04(λ –1 250)
C6 = α/αmin
T2 = 10 * 10 [(α-αmin)/98.5] s
t = 100s

Wavelength [nm]: 1271 nm

Fiber Spacing [µm]: 250 µm
Fiber Diameter (MFD) [µm]: 9.6 µm

For Laser Class 1/Hazard Level 1M evaluations of MPO connectors two neighboring emitters present the
worst-case configuration.

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11.7.3 Every Second Fiber Active

AEL Calculations
Point Source (single fiber)
α ≤ 1.5 mrad: AEL = 3.9 * 10-4 C4 C7 W
Extended Source (multiple fibers)
α > 1.5 mrad: AEL = 3.5 * 10-3 C6 C7 T2-0.25 W
C4 = 5
C7 = 8 + 100.04(λ –1 250)
C6 = α/αmin
T2 = 10 * 10 [(α-αmin)/98.5] s
t = 100s

Wavelength [nm]: 1271 nm

Fiber Spacing [µm]: 250 µm
Fiber Diameter (MFD) [µm]: 9.6 µm

For Laser Class 1/Hazard Level 1M evaluations of MPO connectors with increased emitter spacing single
emitters present the worst-case configuration.

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11.7.4 Four Active Fibers with Maximum Separation

AEL Calculations
Point Source (single fiber)
α ≤ 1.5 mrad: AEL = 3.9 * 10-4 C4 C7 W
Extended Source (multiple fibers)
α > 1.5 mrad: AEL = 3.5 * 10-3 C6 C7 T2-0.25 W
C4 = 5
C7 = 8 + 100.04(λ –1 250)
C6 = α/αmin
T2 = 10 * 10 [(α-αmin)/98.5] s
t = 100s

Wavelength [nm]: 1271 nm

Fiber Spacing [µm]: 250 µm
Fiber Diameter (MFD) [µm]: 9.6 µm

For Laser Class 1/Hazard Level 1M evaluations of MPO connectors with increased emitter spacing single
emitters present the worst-case configuration.

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11.8 AEL Calculations for MPO Connector – Condition 2: Aperture Distance 35 mm

11.8.1 All Fibers Active

AEL Calculations
Point Source (single fiber)
α ≤ 1.5 mrad: AEL = 3.9 * 10-4 C4 C7 W
Extended Source (multiple fibers)
α > 1.5 mrad: AEL = 3.5 * 10-3 C6 C7 T2-0.25 W
C4 = 5
C7 = 8 + 100.04(λ –1 250)
C6 = α/αmin
T2 = 10 * 10 [(α-αmin)/98.5] s
t = 100s

Wavelength [nm]: 1271 nm

Fiber Spacing [µm]: 250 µm
Fiber Diameter (MFD) [µm]: 9.6 µm

For Hazard Level 1 evaluations of MPO connectors single emitters present the worst-case configuration.

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11.9 Burn Hazard Labeling

Warning for potential hazard to the skin or anterior parts of the eye
For Class 1, 1M, 2, 2M or Class 3R, if the accessible emission exceeds the AEL of Class 3B as determined
with a 3,5 mm diameter aperture placed at the closest point of human access, an additional warning
shall be given on a product label and in the information for the user (see 5.3 a) for Class 1 and 1M, see
5.3 c) for Class 2 and 2M, and see 5.3 d) for Class 3R).
The following warning shall be given on the product housing and in the information for the user. Text
borders and symbols shall be black on a yellow background, including for Class 1.
LASER ENERGY - EXPOSURE NEAR APERTURE MAY CAUSE BURNS
NOTE The risk of skin injury is only likely for highly divergent beams for exposure close to the aperture.
While the placement of the explanatory label for Class 1 and 1M on the product is optional (see 7.2), the
above warning is not optional.

11.10 AEL Calculations for Short Time Exposure (Laser class 1/1M)
AEL Calculations
Wavelength [nm]: 1271nm
Point Source (single fiber)

α ≤ 1.5 mrad: EAEL = 3.5 * 10–3 t 0,75 C7 J

C7 = 8 + 100.04(λ –1 250)
t = 10s - 0.1ms
PPeak = EAEL/t
P0Peak based on Condition 3 (100mm, 9.6µm)

Calculations a based on single pulse exposure as per IEC 60825-1

APR regulations as per IEC 60825-2 have not considered as the
FDA/CDRH does not recognize IEC 60825-2 for FDA filings under
laser notice #56.

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11.11 Sample Scenarios for ELS Modules with Accessible MPO Connectors
11.11.1 Eight Fibers at 18 dBm Each (Wavelengths 1271 nm, 1291 nm, 1311 nm, 1331 nm)

1271nm represents the most restrictive wavelength

Hazard Level 1 Hazard Level 1M

Limit Limit
Laser Class 1 Limit

Hazard Level 1 emission levels are exceeded for continuous emission

Laser Class 1 & Hazard Level 1M emission limits are maintained for continuous emission
Hazard Level 1 emission limits are maintained if the exposure is limited to 2s or less.
Total Accessible Power > 500 mW => Burn Hazard Label required

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11.11.2 Eight Fibers at 22 dBm Each (Wavelengths 1271 nm, 1291 nm, 1311 nm, 1331 nm)

1271nm represents the most restrictive wavelength

Hazard Level 1
Limit Hazard Level 1M
Limit
Laser Class 1 Limit

Hazard Level 1/1M and laser class 1 emission levels are exceeded for continuous emission
Emissions are within limits for Laser Class 1 & Hazard Level 1M if the exposure is limited to 0.3s or less.
Emissions are within limits for Hazard Level 1 if the exposure is limited to 50ms or less.
Total Accessible Power > 500 mW => Burn Hazard Label required

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11.11.3 Four Fibers at 24 dBm Each (Wavelength 1311 nm Only)

Hazard Level 1 Hazard Level 1M

Limit Limit
Laser Class 1 Limit

Laser Class 1 & Hazard Level 1/1M emission limits are maintained for continuous emission

Total Accessible Power > 500 mW => Burn Hazard Label required

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12 Appendix C: List of companies belonging to OIF when document is approved

Accton Technology Corporation Hisense Broadband Multimedia NVIDIA Corporation

Technologies Co., LTD
ADVA Optical Networking Huawei Technologies Co., Ltd. O-Net Communications (Shenzhen)
Limited
Advanced Fiber Resources (AFR) I-Pex Open Silicon Inc.
Alibaba IBM Corporation Optomind Inc.
Alphawave IP Inc. Idea Sistemas Electronicos S.A. Orange
Amphenol Corp. II-VI Incorporated PETRA
AnalogX Inc. Infinera Pointwo Technology
Applied Optoelectronics, Inc. InnoLight Technology Limited Precise-ITC, Inc.
Ayar Labs Innolume GmbH Quintessent Inc.
Banias Labs Innovium Ragile Networks, Inc.
BitifEye Digital Test Solutions Integrated Device Technology Rambus Inc.
GmbH
Broadcom Inc. Intel Ranovus
Cadence Design Systems IPG Photonics Corporation Retym
China Telecom Juniper Networks Rockley Photonics
CICT Kandou Bus Rosenberger Hochfrequenztechnik
GmbH & Co. KG
Ciena Corporation KDDI Research, Inc. Samsung Electronics Co. Ltd.
Cisco Systems Keysight Technologies, Inc. Samtec Inc.
Commscope Connectivity Kuaishou Technology Semtech Canada Corporation
Belgium BVBA
Cornelis Networks, Inc. Lumentum Senko Advanced Components
Corning Luxshare-ICT Sicoya GmbH
Credo Semiconductor (HK) LTD MACOM Technology Solutions SiFotonics Technologies Co., Ltd.
Dell, Inc. Marvell Semiconductor, Inc. Socionext Inc.
DustPhotonics Maxim Integrated Inc. Source Photonics, Inc.
EFFECT Photonics B.V. MaxLinear Inc. Spirent Communications
Eoptolink Technology MediaTek Sumitomo Electric Industries, Ltd.
Epson Electronics America, Inc. Meta Sumitomo Osaka Cement
ETRI Microchip Technology Incorporated Synopsys, Inc.
EXFO Microsoft Corporation TE Connectivity

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Foxconn Interconnect Mitsubishi Electric Corporation Telefonica S.A.

Technology Ltd
Fujikura Molex TELUS Communications, Inc.
Fujitsu Multilane Inc. US Conec
Furukawa Electric Japan NEC Corporation Viavi Solutions Deutschland GmbH
Global Foundries NeoPhotonics Wilder Technologies, LLC
Global Unichip Corp (GUC) Nitto Denko Corporation Xelic
Google Nokia Xilinx
Hakusan Inc NTT Corporation Yamaichi Electronics Ltd.
Hewlett Packard Enterprise Nubis Communications, Inc. ZTE Corporation
(HPE)

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