Signal acquisition method and automatic masking system for an otdr

Abstract

An automatic masking system is used in an optical time domain reflectometer for implementing a method of compensating for relaxation transients in an optical receiver in the OTDR. The masking system drives an optical modulator that masks the optical reciver from high amplitude optical pulses in the return reflected light from a fiber under test. A masking pattern corresponding to the high amplitude optical pulses is generated from a first acquisition of data with the receiver unmasked from the return reflected light. The masking pattern is stored and used for generating a signal from the masking system to the optical modulator for blocking the high amplitude optical pulses in the return reflected light during a subsequent acquisition of data. In a third acquisition of data of the return reflected light, the optical modulator masks the receiver from the return reflected light. Combining the acquired data of the blocked return reflected light with the acquired data with the high amplitude optical pulses blocked, produces an output free of relaxation transients produced by the receiver. Combining the high amplitude optical pulse data from the first acquisition with the output from the subtracted acquisitions produces an output representative of the return reflected light.