| 摘要 |
PURPOSE:To automatically control a wavelength transmission characteristic of a filter, and also, to increase the capacity of the filter by allowing transmission bands and transmission peaks of two filters having a specific characteristic to coincide with each other. CONSTITUTION:A first filter 1 has a single peak response transmission band characteristic 10 in a necessary band, and has such a characteristic as a half-amplitude level of a desired attenuation quantity of a transmission band becomes double or below of a channel interval of a multiplexed optical signal. Also, a second filter 2 has a periodical transmission characteristic 20, and odd number multiple of 1/2 of its free spectral range FSR corresponds to a channel interval 30 of the multiplexed optical signal. In this case, when spectral width of a signal light by a transmission rate is taken into consideration, transmission width of the filter 2 goes down, and goes down against a transmission peak, therefore, a channel interval is calculated. As a result, since the transmission band of the filter 1 and the transmission peak 2 of the filter 2 are matched with each other, a desired optical signal subjected to optical frequency multiplexing at an equal interval can be selected and received. Also, the peak of transmission wavelength of the filter 2 is subjected to selection control and the filter having a large capacity can be obtained. |
