International Journal of Scientific and Research Publications, Volume 5, Issue 1, January 2015 1
ISSN 2250-3153
Performance Analysis of 20Gbps Optical Transmission
System Using Fiber Bragg Grating
Aashima Bhardwaj1, Gaurav Soni2
Dept. of Electronics & Communication Engineering, A.C.E.T
Abstract- This paper discussed on a simulation of optical such as WDM/TDM or CATV network, dispersion map design,
transmission system in optical fiber. To achieve the foremost transmitter, receiver and amplifier design and others . Optisystem
effective performance of communication system, dispersion should is a product that does not depend on other simulation design. It is
be stipendiary. Fiber bragg grating is chosen as important based on realistic optical fiber modeling as a communication
components to compensate the dispersion in optical communication system. There are hundreds of official components in Optisystem
system. The simulation of transmission system will be analyzed
component library.
based on different parameters by using optisystem simulator. A 20
Gb/s Non Return To Zero (NRZ) signal is launched onto 50 km long In this paper, the simulation of the optical transmission system
standard single mode fiber. By simulating a model of in optical fiber has been discussed by analyzing the effect of the
communication system and using the most suitable settings of the components in data receiver by using different parameters
system which include input power (dbm), fiber cable length, the setting. The value of Q-factor has been investigated at receiver.
performance of the system will be evaluated. Comparison of eye
diagrams show a marked improvement in the link performance due
to compensation of dispersion.
II. FIBER BRAGG GRATING
Index Terms- Optical transmission System, Fiber Bragg Fiber Bragg Grating (FBG) is very simple and low cost filter
Grating, Dispersion compensation, Optisystem Simulator. for wavelength selection which has various applications to
improve the quality and diminish the costs in optical networks
[6]. FBG executes some operations like reflection and filtering
I. INTRODUCTION with high efficiency and low loses. FBG acts as a dispersion
Fiber optic communication is a method of transmitting compensator in transmission optical system which is used to
information from one place to another by sending light through compensate chromatic dispersion. Thus, the final expected effect
an optical fiber. The basic optical transmission system consists of is compression in incident pulse and can be appropriate to
three basic elements which are fiber media (transmission compensate chromatic dispersion in a communication link [6].
channel) , light sources as the input (covert electric signal into FBG is single mode which will expose the core to the periodic
optic signal) and light detector as the output ( convert optic pattern of intense ultraviolet light. The exposure will increase the
signal into electric signal). FBG is the key component in optical refractive index and thus the refractive index is permanently
communication system as, dispersion compensators, filters and increased. Then the exposure pattern will create a fixed index
flatteners gain. In the transmission section, the gratings are modulation that called grating. When periodic refraction is
placed in the line with the fiber. It will help to achieve the changed, a small reflected light will be produced. Then, the small
maximum compression ratio [1].Because of dependence of group reflected light will be combined into a large reflected light at a
Index to wavelength chromatic dispersion takes place in optical certain wavelength. The certain wavelength is when the grating
fiber it creates an extension of time on pulses [2]. period is approximately half the input light’s wavelength which
Electromagnetic carrier wave is modulated to carry information. is called Bragg’s wavelength. The other light (except the Bragg’s
Chromatic dispersion and polar mode dispersion occurs in single light) will be transparent.
mode fiber (SMF). In optical system dispersion can be
compensated by also using erbium doped fiber amplifier (EDFA)
[3]. The frequency increases along the pulse when the dispersion
coefficient parameter of the fiber is negative [4]. Chromatic
dispersion is wavelength dependent and is ruling the single mode
fiber [5]. Optisystem simulator software is an advanced,
innovative, rapidly developing and powerful software simulator
tool for the design, testing and optimization of virtually any type
of optical link in the physical layer of a broad spectrum of optical
networks from ultra-long-haul system to local area networks Figure1: Principle of operation of FBG [8]
(LANs) and metropolitan (MANs) [6]. OptiSystem offers optical When a light pulse propagates down an optical fiber, it is
transmission system design and planning from component to dispersed, that is the width of the pulse broadens because the
system level and present the analysis and scenarios visually. It longer wavelength light lags the shorter wavelength light.
can help the users to plan, test and simulate several applications Consequently, at sufficiently high data rates and fiber lengths,
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International Journal of Scientific and Research Publications, Volume 5, Issue 1, January 2015 2
ISSN 2250-3153
the pulses in a data stream will begin to overlap. In this way, transmission. The fiber Bragg grating is used as the dispersion
fiber dispersion limits the maximum data that can be transmitted compensator. The FBG length 6 mm Photo detector (PIN) Diode
through a fiber. A dispersed light pulse with the longer Positive Intrinsic Negative to translate the optical signal into an
wavelengths lagging the shorter wavelengths is incident on a electrical signal.
chirped fiber bragg grating [7]. The longer wavelength light is
reflected near the front of the grating whereas the shorter
wavelengths are delayed relative to the longer wavelengths. The
chirped grating can be designed so that all wavelengths in the IV. DSSIGN CONSIDERATION
light pulse exit the reflector at the same time and the dispersion The system is operated with the basic optical communication
in the optical pulse is equalized. which consists of a transmitter, transmission link and a receiver.
The system transmits information using optical carrier wave from
transmitter to receiver via optical fiber. The input signal contains
electrical data that is represented by 0’s and 1’s has been
generated by a non-return-zero (NRZ) pseudorandom binary
sequence. Then the input signal is modulated with semiconductor
laser that is represented by Continuous Wave (CW) laser through
Mach- Zehnder modulator. CW laser supplies input signal with
1550 nm wavelength and input power of 5dBm which is
externally modulated at 20 Gbits/s with a non-return-zero (NRZ)
pseudorandom binary sequence in a Mach-Zehnder modulator
with 5 dB of extinction ratio. The optical fiber used is single
mode fiber because single mode fiber can yield higher data rate,
less dispersion and also can operate in long haul distance, so it is
suitable to be used as transmission link.
For the dispersion compensator, the fiber Bragg grating will be
used. The length grating that will be used is 6 mm since the most
proper length for proposed model is equal to l = 6 mm by try and
Figure 2: principle of Bragg’s light error method [1]. After dispersion compensation the signal will
pass through optical amplifier that represented by Erbium-doped
fiber amplifier (EDFA). Optical amplification is required to
There are numbers of software available which can mimic the overcome the fiber loss and also to amplify the signal before
process involved in your research work and can produce the receive by Photo detector PIN at the receiver part.
possible result. One of such type of software is Matlab. You can
readily find Mfiles related to your research work on internet or in
some cases these can require few modifications. Once these
Mfiles are uploaded in software, you can get the simulated
results of your paper and it easies the process of paper writing.
As by adopting the above practices all major constructs of a
research paper can be written and together compiled to form a
complete research ready for Peer review.
III. DESCRIPTION OF COMPONENTS
NRZ pulse generator has an advantage on controlling bandwidth.
This is due to the characteristic of the generator that the returning
signals to zero between bits. Pseudo-random bit sequence Figure3: The optical transmission system block diagram [8]
generator is used to scramble data signal in terms of bit rates.
Mach Zender Modulator (MZ) has two inputs (optical signal and
electrical signal) and one output (optical). Then the input signal
is modulated with semiconductor laser that is represented by
Continuous Wave (CW) laser Frequency 193.1 THz through
Mach- Zehnder modulator. Continues laser diode (CW) to
generate optical signals supplies input signal with 1550 nm
wavelength and input power of 10dBm which is externally
modulated at 20 Gbits/s. with a non-return-zero (NRZ)
pseudorandom binary sequence in a Mach-Zehnder modulator
with 7 dB of extinction ratio. The optical fiber used is single
mode fiber because has higher data rate and long distance
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International Journal of Scientific and Research Publications, Volume 5, Issue 1, January 2015 3
ISSN 2250-3153
V. SIMULATION OF TRANSMISSION SYSTEM
Figure5: Eye diagram analyzed at 10 Km
Figure 4: The designed model of simulated system .
TABLE 1: SIMULATION PARAMETERS
C/W Input Power 5dbm
C/W laser Frequency 193.1THZ
Reference Wavelength 1550 nm
Mach-Zender modulator with of extinction 7db
ratio
Fiber length 50 km
Attenuation at cable section 0.2db/km
EDFA length 5m
FBG length 6mm
VI. RESULTS AND DISCUSSIONS
The simulation and optimization of the design is done Figure6: Eye diagram analyzed at 20 Km.
by Optisystem simulation software. The eye diagrams
and results are tabulated into Table.
. TABLE 2: The output readings are tabulated by varying the
OFC Length (Km).
OFC Length Q-Factor
10 23.8289
20 19.819
30 12.7887
40 8.66328
50 7.21557
Figure7: Eye diagram analyzed at 30 Km.
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International Journal of Scientific and Research Publications, Volume 5, Issue 1, January 2015 4
ISSN 2250-3153
a light detector. From the simulation result, it can conclude that
the optical fiber length is inversely proportional to the Q-Factor.
The Q-Factor is the measure of the system. performance.
REFERENCES
1. M. Litchinitser, J. Eggleton, and B.Patterson,“ Fiber Bragg
Gratings for Dispersion Compensation in Transmission :
Theoretical Model and Design Criteria for Nearly Ideal Pulse
Recompression,” Journal OfLightwave Technology, Vol. 15,
No. 8, August 1997
2. S. O. Mohammadi, Saeed Mozaffari and M. Mahdi Shahidi
“Simulation of a transmission system to compensate dispersion
in an optical fiber by chirp gratings “. International Journal of
the Physical Sciences Vol. 6(32), pp. 7354 - 7360, 2
December, 2011.
3. Huang Liqun, Song Xin, Liu Fulai, Shen Li, and Han Laiquan
Figure8: Eye diagram analyzed at 40 Km. “Computer Simulation of 40Gb/s Optical Fiber Transmission
Systems with a Fiber Grating Dispersion Compensator “20IO
International Conference On Computer Design And
Applications (ICCDA 2010).
4. S Sujith and K G Gopchandran “A Simulation study on DCF
compensated SMF using OptSim”. 2010 International congress
on Ultra Modern Telecommunications and Control Systems
and Workshops (ICUMT) 978-1-4244-7286-4/10 ©2010 IEEE
Department of Optoelectronics, University of Kerala,
Thiruvananthapuram - 695 581, India).
5. Gnanam Gnanagurunathan, Faidz Abd. Rahman “Comparing
FBG and DCF as dispersion compensators in the long haul
narrowband WDM systems” 2006 .
6. S. O. Mohammadi, Saeed Mozzaffari and M. Mahdi Shahidi,
“Simulation of a transmission system to compensate dispersion
in an optical fiber by chirp gratings.” International Journal of
the Physical Sciences, Vol. 6(32), pp. 7354 - 7360, 2
Figure9: Eye diagram analyzed at 50 Km December, 2011.
7. K. O. Hill, F. Bilodeau, B. Malo, T. Kitagawa, S. Th´eriault, C.
Johnson, J. Albert, and K. Takiguchi, “Aperiodic in-fiber
CONCLUSION Bragg gratings for optical fiber dispersion compensation,” in
Conf. Optic. Fiber Commun., OFC’94, San Jose, CA,1994.
From design and simulation of optical transmission system, the 8. M.A. Othman, M.M. Ismail, H.A. Sulaiman, M.H.
journals related about optical transmission system have been Misran,M.A. Meor Said, Y.A. Rahim, A.N. Che Pee, M.R.
discovered and studied in order to propose the design idea for a Motsidi ,“An Analysis of 10 Gbits/s Optical Transmission
simulation of optical transmission system. The system will System using Fiber Bragg Grating (FBG) ,” www.iosrjen.org ,
transmit information using optical carrier wave from transmitter to ISSN: 2250- 3021 Volume 2, Issue 7(July 2012), PP 55-61 .
receiver via optical fiber. Based on the research, the transmission .
system block diagram has been designed which consists of laser
light as a source, modulator, single mode optical fiber as the
channel, fiber bragg grating as the dispersion compensator,
Erbium Doped Fiber Amplifier (EDFA) and the photo detector as
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