TESTING METHOD OF REFLECTION WITH HIGH RESOLUTION AND APPARATUS THEREFOR

Japanese Patent JPH01145545

A

PURPOSE:To realize a testing method of reflection with high distance resolution, by a method wherein a difference between the delay times of a reflected light signal from an optical fiber and a reference light from their emission to reception is adjusted to be zero or a value close thereto. CONSTITUTION:An optical wave divider 2 divides an emission light from a light source 1 into a probing light and a reference light. A light frequency shifter 3 shifts the frequency of the probing light by DELTAf from a frequency (f) of the light source 1, and the probing light is made to enter an optical fiber 5 through an optical directional coupler 4. In this constitution, an optical delay circuit 9 is adjusted so that a beat electric signal by a composite wave formed of the probing light reflected or back- scattered at some point in the fiber 5 and of the reference light be the maximum, and then the optical delay circuit 9 is adjusted so that a belt due to reflection or the like at another point in the fiber 5 be the maximum. When a difference between a delay time for one point and a delay time for another point is denoted by DELTAT and a light velocity in the fiber 5 by V, on the occasion, a distance between one point and another point can be determined by V.DELTAT/2, and a high distance resolution is obtained even by using a light source of which a coherence time is short.

HORIGUCHI TSUNEO
SHIBATA NOBURU
TATSUTA MITSUHIRO

JP30154787A

June 07, 1989

December 01, 1987

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NIPPON TELEGRAPH & TELEPHONE

G01M11/00; G01M11/02; G01N21/27; G02B6/00; (IPC1-7): G01M11/00; G01M11/02; G01N21/27; G02B6/00

Yoshikazu Tani

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