Specialty Optical Fibers Handbook

because it can transmit beyond the 20 mm range required for the intended

military surveillance satellite application. Today the best PC fibers, made from

silver halide crystals, have losses in the 0.3 dB/m range at 10.6 mm. Nevertheless,

the Ag-halide PC fibers continue to be popular today for short-length applica-

tions in sensor systems and for limited use in low-power laser delivery.

There has been comparatively less work on SC fiber optics. One reason for

this is that they are much harder to fabricate than PC fibers. Only a few

crystalline host materials have been studied, with the most important being the

refractory oxides. Of these, sapphire fiber (Al

2

O

3

) is the most studied SC fiber,

and it has the lowest loss [8, 25–27].

13.4 POLYCRYSTALLINE ...