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One critical factor when looking
at the alternative fibre jointing technologies is how much light
is lost at each joint. Light loss is measured in decibels (dB)
- a decibel is 10 times (hence "deci") the logarithm
of the fraction of light lost in the joint. Decibels are used
because you can simply add the dB losses of each joint together
to find out the overall loss in a system.
There are basically two types of connection for optical fibre
- demountable (connectors) and permanent (splices). |
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| Connectors are used when
connecting to the end equipment (the transmitters and
receivers). The system can then be disconnected or reconfigured.
Typically, the losses when using connectors are 0.15 dB
- 0.50 dB. Connectors can also be used in temporary fibre-to-fibre
connections. |
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| Splices are used to permanently
join two lengths of optical fibre together, or often to
attach connectorised leads (called pigtails) to the ends
of installed fibre runs. One method is known as mechanical
splicing, where a mechanical jig (with a ferrule or a
v-groove) is used to align and butt the fibres together,
and hold them permanently in place. Index matching fluid
can be used to reduce the boundary reflections between
the two fibres. Losses with mechanical splicing are typically
0.10 dB - 0.25 dB. |
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| But the most popular way to
make a permanent joint is known as fusion splicing… |
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