Nec Corporation

Yuhei Matsumoto

Takefumi Oguma

Kazunori Shinya

An optical detection unit detects a return light and outputs a detection signal. An optical multiplexer/demultiplexer outputs the monitoring light to the optical transmission line, and outputs the return light to the optical detection unit. A processing unit detects a first timing at which the detection signal becomes less than a first threshold value, detects a second timing at which the detection signal becomes less than a second threshold value, and calculates a first change rate of the detection signal in a period between the first and second timings. The processing unit changes the first and second threshold values to calculate the first change rate for a plurality of periods, and, when a second change rate between the first change rates in two adjacent periods is greater than a threshold value, either of the first and second timings in one period is detected as the breakage position.

Optical time domain reflectometer, test method of optical transmission line, and test system of optical transmission line

An object is to automatically detect a failure of an optical transmission line. A light source outputs a monitoring light. An optical detection unit detects a return light from an optical transmission line and outputs a detection signal indicating an intensity of the return light. An optical multiplexer/demultiplexer outputs the monitoring light input from the light source to the optical transmission line, and outputs the return light input from the optical transmission line to the optical detection unit. A comparator compares the detection signal with a threshold voltage and outputs a comparison signal indicating the comparison result. A processing unit detects a first timing at which the comparison signal changes, and detects a failure of the optical transmission line when the first timing is earlier than a reference timing.

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Tokyo, Japan

Yuhei Matsumoto