| 摘要 |
PURPOSE:To compensate the initial value deviation of a light source wavelength and its temperature dependency by tuning a wavelength selected by a Fabry- Perot variable interference filter with a wavelength of an optical signal to be received and allowing a photodetector to receive a light. CONSTITUTION:A signal from callers 101-103 is converted into an optical signal by light emitting diodes 11-13. A photo star coupler 35 collects lights of each wavelength into one and split by an optical branching device. The optical signal is sent from a transmission station 1 to a reception station 2 by optical fibers 40-42. The optical signal sent to the reception station 2 is subject to wavelength selection by a Fabry-Perot type variable interference filter 50 and the result is made incident in a photodetector 70. A filter control circuit 92 scans the transmission spectrum of the filter 50 so as to be approached to the light wavelength, repeats the scanning to be tuned with the light wavelength. Even when the light wavelength is changed due to temperature change of the light emitting diode or the like, since the filter 50 traces the wavelength, the reception state is unchanged. |
