TI CS L
OP
TD
OZ
.
CA
OZ OPTICS LTD.
N ADA
APPLICATION
NOTE
FC/APC
CONNECTORS
VERSUS
FLAT ANGLED FINISH
FC CONNECTORS
The information/data furnished in this document shall not be duplicated, used or disclosed in whole or in part for any purpose other than to which
it was intended.
F:\USERS\GENERAL\INSTRUCT\APPNOTES \APC vs AFC.DOC May 29, 2003
Issue: Rev. 1
Page 1 of 4
Connectors with angle polished (APC) finishes are a very popular choice in the market today. Connectors with APC
finishes are made by polishing the fiber at either an 8 or 9 degree angle, with a radius of curvature between 5 and
12 mm (See figure 1). By angle polishing the end of the fiber, one ensures that reflections at the fiber-air interface
are not captured by the fiber core. This greatly reduces backreflection levels in fiber optic systems, and in turn
reduces feedback problems and improves stability. By having the angled surface polished to a radius, one also
ensure that two similarly polished connectors will mate at the fiber core.
Figure 1: APC Ferrule Polish
One drawback with angled polished connectors is that the tip of the fiber is not in the same plane as the tip of the
ferrule. Therefore when one butts the ferrule against a flat stop, such as in a collimator receptacle, there is a gap
between the stop and the end of the fiber. Furthermore the variation in the endface geometries from one APC
connector to the next affects the size of this gap (See Figure 2a). Different manufacturers also vary the very profile
of the tip, further introducing errors (Figure 2b). These variations can cause the gap size to vary by as much as 100
microns. This can significantly reduce coupling efficiencies in laser to fiber couplers.
F:\USERS\GENERAL\INSTRUCT\APPNOTES\APC vs AFC.DOC May 29, 2003
Issue: Rev. 1
Page 2 of 4
(a) Effect of Different Endface Radii
(b) Different Commercial Ferrule End Shapes
Figure 2: Variations in APC Ferrule Endface Geometries
To provide the low return losses of APC connectors without the problems in the gap spacing, OZ Optics offers an
angled flat (AFC) polished connector. This connector features a beveled endface where the fiber face itself is
angled, but the ferrule tip is flat. (See Figure 3). The region that is angle d polished extends past the fiber cladding
to a maximum of one fiber radius. This geometry reduces the variation in the gap location to less than 15 microns,
greatly improving the repeatability in coupling efficiency. The relatively large flat surface also ensure better contact
against a stop than the point contact an APC connector makes.
F:\USERS\GENERAL\INSTRUCT\APPNOTES\APC vs AFC.DOC May 29, 2003
Issue: Rev. 1
Page 3 of 4
Figure 3: AFC Finish Geometry
The sole drawback of the AFC design is that the flat surface does not allow the same quality of mating between two
fibers as the APC finish provides. Thus while AFC finish connectors are recommended for free space to fiber
applications, the APC finish is still recommended for fiber to fiber connections.
F:\USERS\GENERAL\INSTRUCT\APPNOTES\APC vs AFC.DOC May 29, 2003
Issue: Rev. 1
Page 4 of 4
