Specialty Optical Fibers Handbook

the back-reflected power to below 60 dB. Because the axis of the butt-coupled

fiber must be oriented according to refraction laws to preserve a low loss connec-

tion, the slant-polished angle of 15 degrees of SiO

2

fiber is required [95, 96].

During the preparation of the input and output fiber subassemblies, a small

tube or block is attached to the end of each fiber. This tube is angle-cut and

polished to minimize back-reflections from the interfaces. The tube increases the

surface area and bond strength of the pigtail and liability. UV or thermal curable

adhesives are used to attach the fiber subassemblies to the chips. To de-couple

the strain induced by the differential thermal expansion among the integrated

optic chip, the fiber, and the packaging ...