Nippon Telegraph and Telephone Corporation

Ando Electric Company

Mitsuhisa Sato

Shinichi Furukawa

Mikio Maeda

The purpose of the present invention is to provide a time domain reflectometer in which the system cost is low and the dynamic range is wide. In accordance with the present invention, an excitation light source for generating continuous light of a predetermined frequency (e. g., 1.48 .mu.m), and a ring laser part for generating a high power light pulse in accordance with the continuous light are provided. A light branch device is held in common by the ring laser part and a measurement part. The light branch device makes the light pulse which has been incident on one of its end parts to be incident on a light cable to be measured; and the light branch device also receives response light and supplies the response light to a light receptor in the measurement part. In the measurement part, the response light is converted to a corresponding electric signal and the signal is amplified to be supplied to a measurement circuit.

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Tokyo, Japan

Mitsuhisa Sato