| 摘要 |
PURPOSE:To attain surely initial setting of an optimum value to a demodulation section in a short time by monitoring an output of the demodulation section while the laser diode temperature of a local oscillation light source is scanned sequentially from a high temperature to a low temperature so as to obtain an optimum local oscillation frequency. CONSTITUTION:At application of power to the optical heterodyne receiver, the temperature of the laser diode integrated in a local oscillation light source 11 is set at an upper limit or a lower limit in the variable enable range by a temperature variable section 13. Then the temperature is scanned sequentially at an interval of a prescribed temperature and an output signal of a demodulation section 5 in each scanning process is monitored. When the monitored signal level reaches a specified signal level, it is discriminated that the intermediate frequency of the intermediate frequency signal enters the real band area in the frequency characteristic. That is, the output of the demodulation section 5 is monitored to detect the optimum local oscillation frequency. Thus, the intermediate frequency of the intermediate frequency signal inputted to the demodulation section is set initially to an optimum value to the integrated demodulation section surely in a short time. |
