Extended optical fiber line testing system using L/U-band crossed optical waveguide coupler for L-band WDM transmission

We proposed an extended optical fiber line testing system using ultra-low-cost crossed optical waveguide couplers with L/U-band thin dielectric film filters for L-band WDM transmission. We described the design of the return loss required for optical filters located in central offices. We also designed and confirmed the effectiveness of the configuration of a crossed optical waveguide coupler and a thin dielectric film filter with a steep optical spectrum to separate a 1650 nm test light from L-band wavelength light. We confirmed that there was no degradation in the OTDR trace caused by multi reflections at optical filters when using our crossed optical waveguide coupler.