Patent ID: 7208722
Filing Date: 2007-04-24
Classification: G01M

Abstract:
1. A method of measuring coherent crosstalk light generated by multiple reflection of light between a plurality of reflection points existing within an object of measurement, comprising: generating measurement light in which the frequency of a light emitted from a laser light source operating under single longitudinal mode oscillation is modulated to a sawtooth wave shape at a variable period; irradiating the generated measurement light into one end of an optical path which passes through the inside of said object of measurement; receiving the light emerging from the other end of the optical path of said object of measurement by an optical receiver and converting to an electrical signal; applying the converted electrical signal to a frequency filter, and extracting a beat component of a frequency corresponding to half the difference between the maximum value and minimum value of the optical frequency of said measurement light; controlling the modulation period of said measurement light so that the power of the extracted beat component becomes a local maximum; and measuring whether or not coherent crosstalk light is generated in said object of measurement, based on the power of the beat component which has become the local maximum due to control of said modulation period.