RAYLEIGH BACKSCATTERING MEASUREMENT OF SINGLE-MODE FIBERS BY LOW COHERENCE OPTICAL TIME-DOMAIN REFLECTOMETER WITH 14-MU-M SPATIAL-RESOLUTION

An optical time-domain reflectometer (OTDR) with - 136 dB minimum detectable reflectivity and 14-mu-m spatial resolution is developed based on low coherence interference. The high sensitivity was accomplished by using a high-power superluminescent diode module with a 1.5 mW fiber output and a new system configuration, both for effectively operating the balanced heterodyne detection. The reflectivity of - 136 dB is only 6 dB above the shot noise limit. The first observation of 1.3-mu-m wavelength Rayleigh backscattering in single-mode fibers was successfully made by the OTDR with a 17 dB dynamic range and 14-mu-m spatial resolution.