Temperature-Independent Temporary Optical Coupler Using Fiber Bending Technique

This paper shows how to reduce the temperature dependence of a temporary optical coupler that enables us to output a signal light from a bent fiber by aligning a probe fiber in the path of the light leaked from the bent fiber and input a signal light from the probe fiber to the bent fiber. We experimentally demonstrate that the temperature dependence of the coupling efficiency between the bent and probe fibers is significantly improved by reducing the misalignment between these fibers created by temperature changes. First, we confirm by comparing calculation results to measured values that the temperature dependence of the conventional structure is caused by misalignment between the bent and probe fibers created by the difference in the thermal expansion of the components. Next, we demonstrate that the temperature dependence of the coupling efficiency is suppressed by using a structure that reduces the misalignment, and the proposed temperature-independent temporary optical coupler provides the coupling efficiency required to support its application over the wide temperature range of -10 to 50 degrees Celsius (equivalent to a fusion splicer) for fibers compliant with ITU-T G. 652 and G. 657.