| Return
loss represents the amount of light that does not get reflected
back at a connection point. The higher this loss, then the lower
the amount reflected. Therefore, the higher the return loss, the
lower the reflection and the better the connection.
Air
gaps between two mating fibre cores will cause reflection back
towards the light source. Flat polished connectors experience
high reflection because the point of contact will not be at the
cores, thus causing an air-gap. This sort of connection will cause
return loss values in the order of 11dB to 15dB. This type of
polish is not suitable for singlemode transmission and is rarely
used in multimode transmission systems.
PC
connectors are spring loaded so that contact is ensured when mated.
This also slightly deforms the ferrule endface to offset any minor
endface defects. PC polished connectors also have a convex endface.
This insures that the point of contact is at the centre where
the fibre core is.
There are three variations of PC polish, each achieving different
values of return loss:
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