In-service Optical Fiber Line Monitoring by Wavelength Division Multiplexing Technique

Abstract

This paper describes the in-service optical fiber monitoring for gigabits/s optical telecommunications where signal and monitor light waves are on a single-mode fiber using wavelength division multiplexing technique. In general, this monitoring is subject to crosstalk, which causes an increase in bit error rate in the signal channel and decreases in dynamic range in loss and reflection distribution measurement using optical time domain reflectometry in monitor channel. First, permissible conditions for the crosstalk power levels of signal and monitor channels were studied theoretically and experimentally. According to these conditions, the performance of optical monitor equipment and components have been clarified. It was found that optical time domain reflectometry using heterodyne detection was efficient for its large dynamic range and maximum crosstalk power level. As a result, a practical in-service monitoring system has been demonstrated.