45° aligned dual-polarizer for the suppression of signal fading in polarization OTDR.

A rotating coordinate system model is used to describe the procedure of polarization detection in polarization optical time-domain reflectometry (POTDR), which reveals the relationship of the system response with respect to the initial state of polarization and the direction of the polarizer. On this basis, a 45° aligned dual-polarizer structure is proposed for the suppression of signal fading in the POTDR system. For ease of practical application, an integrated space optics scheme is implemented with the combination of three collimators, one beam splitter, and two polarizers whose principal axes are 45° aligned. Experimental results show that the possibility of signal fading occurrence is reduced from 35.5% in a traditional POTDR down to 6.5% using the proposed scheme.