Spatial Resolution Enhancement Based on Peak Splitting in Low-Coherence Interferometry Signal

Low-coherence interferometry (LCI) has been a useful tool to detect distributed polarization coupling (DPC) points in polarization-maintaining fiber (PMF). However, due to birefringence dispersion, two close coupling points in long PMF are usually difficult to be distinguished. A novel method in our paper has been presented to tackle the problem. When the product of birefringence dispersion and fiber length called accumulated dispersion (AD) is numerically enough, the coherence envelopes caused by two close coupling points will split into periodic multiple peaks in the overlapping region, and the distance of the two coupling points can be further demodulated from the frequency of splitting peaks. An experimental setup based on LCI has been established with two Panda PMFs of 600 and 950 m under test. Experimental results show that the measuring errors of two close coupling points distance were less than 5%. When AD reached as high as 29 and 46 fs/nm, the spatial resolution was increased by 13-fold and 20-fold, respectively. The constraint conditions to ensure the appearance of peak splitting are also discussed. It indicates that our method may show a potential application of spatial resolution enhancement in high dispersive LCI without dispersion compensation.