Performance improvement of a combined OTDR for distributed strain and loss measurement by randomizing the reference light polarization state

We successfully improve the ability of an OTDR, which combines both BOTDR and COTDR functions, to measure strain and optical loss distribution along optical fibers, by randomizing the polarization state of the reference lightwave for optical coherent detection. The OTDR is upgraded to provide a high-spatial resolution of up to 1 m in the BOTDR mode and a fading noise as low as 0.05 dB in the COTDR mode.