| 摘要 |
PURPOSE:To enable improvement ratio of dynamic range to be expanded and distance resolution to be improved by adding output of a first correlator and that of a second correlator for forming a reflection light of a transmission light pulse at a single optical pulse equivalently. CONSTITUTION:Four types of wavelengths lambda1-lambda4 are modulated by four electrochemical modulators 5-8 by four types of codes which are obtained by offsetting two types of complimentary codes, namely A code and B code, for obtaining one optical signal by a synthesizer 9. Reflection light from an optical fiber to be measured 12 is branched into four kinds of wavelengths lambda1-lambda4 by a branching filter 13 and they are converted to electrical signal by photoelectric converters 14-17. Then, output of the first and second photoelectric converters 14 and 15 is subtracted by a subtractor A18, auto-correlation is performed by a correlator A20, output of the third and fourth photoelectric converters 16 and 17 is subtracted by a subtractor B19, and then auto-correlation operation is performed by a correlator B21. Then, output of the correlator 20 is added to that of the correlator 22, thus enabling a reflection light of a transmission optical pulse to be formed as a single pulse with a large amplitude equivalently. |
