Large fluctuations in transmitted power at fiber Joints with polished endfaces

Measurements and simulation of multipath interference for 1.7-Gb/s lightwave transmission systems using single- and multifrequency lasers

“…For fiber endface-to-air interfaces, power reflection is typically 3 . 3 % , but can be as high as 5% for polished ends [8]. A noncontacting (gapped) connector has two such interfaces, and the total power reflection can range from 0 to 18% owing to coherent addition or subtraction of the light scattered within the gap.…”

“…A noncontacting (gapped) connector has two such interfaces, and the total power reflection can range from 0 to 18% owing to coherent addition or subtraction of the light scattered within the gap. Measurements of noncontacting connector reflections show reflected powers as high as 22% due to index changes of the polished fiber end surfaces [8]. Assuming no fiber loss, a can be as large as 22 % .…”

“…In practice, even contacting connectors have reflections of about 0.16% corresponding to a 28-dB return loss. These reflections are due to mismatching of the fiber endface indexes that result from a variety of mechanisms [8], [29]. The above relation for P ( rnc) can be used to derive a probability-density function for a = G, the geometric mean of the reflectivities of two random air gaps which is a necessary condition for MPI.…”

“…Systems that use demountable optical connectors that rely on physically contacting fiber endfaces for low-reflection connections are particularly vulnerable to MPI since low-reflection connections cannot be guaranteed in every case. Typical return loss for a physically contacting connector is > 28 dB [8]. However, depending on the polishing techniques used there is a potential of up to 22% reflection from connectors that are noncontacting [8].…”

“…Typical return loss for a physically contacting connector is > 28 dB [8]. However, depending on the polishing techniques used there is a potential of up to 22% reflection from connectors that are noncontacting [8]. Since MPI only occurs in systems with two or more optical discontinuities, significant MPI degradation is less likely to occur than degradations due to optical feedback [9]-[ 111.…”