| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce noise contained in light to be measured in a heterodyne type optical spectrum analyzer. Ž<P>SOLUTION: A coupler 3 individually receives light from a variable-wavelength light source 2 and the light to be measured, combines them, and outputs first combined light and second combined light. A first light receiving part 4a receives the first combined light and converts it into a first electric signal. A second light receiving part 4b receives the second combined light and converts it into a second electric signal. A differential amplifier 6 takes the difference between the first electric signal and the second electric signal and outputs a heterodyne signal. This construction includes a variable gain part 5 which varies the magnitude of the first electric signal or the magnitude of the second electric signal and inputs it into the differential amplifier, and which is provided in the portion from a position where the coupler performs multiplexing combining up to the output point of the differential amplifier, and reduces noise contained in the heterodyne signal. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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