User's Manual

Powerwave Fiber Optics
VM100 56/EN – User’s Manual Rev. P1A9-Draft 2004-11 7 - 7
The best of the copper coaxial cables, RG-8, has an attenuation of approximately 100dB/
km at a frequency of 300MHz. This means that only 0.00000001% of the source power
remains after a distance of 1km. In a 1550nm single-mode fiber cable of the same length,
approximately 95% of the source power remains. This example is applicable for a
splice-less cable with no other devices connected.
Miscellaneous fiber cable characteristics
Minimum bend radius for this cable type is 12mm.
The operating temperature range for the most common 9/125µm fiber cabels is –60°C
to +85°C. The lowest temperature causes more trouble than the highest temperature.
Permanent splices
When a fiber cable has to be lengthened, the lowest attenuation and backreflection is
obtained by performing a permanent fiber to fiber splice. Connectors can be used for the
same purpose, but normally they have higher attenuation and backreflection. Permanent
splices are also less expensive.
There are two main types of permanent fiber to fiber splices, fusion splice and
mechanical splice.
Fusion splice
Fusion splice implies that the two cleaved fiber ends are butted together and heated
until they fuse. To be able to perform this type of splice, a fusion splicer is required.
This device has, in addition to an alignment and welding mechanism, also camera
or microscope for supervision of the alignment and fuse procedures, and
instruments to measure the power through the fiber splice.
The attenuation through a correctly performed fusion splice can be as low as
0.05dB.
Mechanical splice
Mechanical splice implies that the two cleaved fiber ends are joined into a structure,
or fixed together with epoxy. To be able to perform this type of splice, a splicer
device is required, which is less expensive than a fusion splicer.
The easiest way to perform a mechanical splice is to use a thin capillary tube in
which the two fiber ends are inserted until they are in contact with each other. This
method is called capillary splicing.
A mechanical splice may have a slightly higher loss and backreflection than a
fusion solice. There is, however, index-matching gel to reduce this loss and
backreflection.