UNDERSTANDING FIBER OPTICS
The coated fiber, i.e. the two active layers (core and cladding) and the protective coating, has an external diameter of 250 microns. It is very fragile. It is thus necessary to build cables to reinforce this fiber and to make it easier to handle. There is a great number of different cable constructions (see below some examples). FIBER OPTIC CABLES
singleway cables:
multiway cables:
0,9 mm buffer
0,9 mm outer diameter
0,9 mm buffer
250 µm coated fiber
250 µm coated fiber
0,3 mm outer diameter
5,5 mm outer sheath
kevlar (strength members)
outer sheath
kevlar (strength members)
HOW TO LINK TWO OPTICAL FIBERS ? There are two ways of linking two optical fibers:
2 - Use of connectors In this case, it is important to terminate a connector at each end of the fibers to be connected. The two fibers can then be connected by connecting the two connectors together. Advantages: •This type of connection is robust. •The type of connector can be chosen according to the application field of the system. • Connection is removable. It is possible to connect and disconnect two fibers hundreds to thousands times without damaging the connectors. Drawbacks: • The implementation is longer than fusion, and requires an experiment as well as specific tools. • The light loss due to connection is higher than in the splicing solution.
1 - Fusion splice This operation consists in directly linking two fibers by welding with an electric arc, by aligning best possible both fiber cores. The specific device to make this fusion is called a fusion splicer.
Advantages:
•This linking method is fast and relatively simple to make. • The light loss generated by the welding, due to an imperfect alignment of the cores, remains very weak. Drawbacks: • This type of link is relatively fragile (in spite of a protection of fusion by a heat-shrinkable tube). • It is a permanent link. • It is necessary to invest in a fusion splicer.
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