| 摘要 |
PROBLEM TO BE SOLVED: To enable the transmission of sub signals without affecting the bit rate of main signals nor requiring any new line or light source by carrying the main signals through light having a prescribed wavelength band, and carrying the sub signals corresponding to the size of specified wavelength components contained in the wavelength band. SOLUTION: A main signal is converted from an electric signal to an optical signal of comparatively wide band by an electric/optic converter 1. In the mean time, the sub signal is converted to a temperature signal by a temperature control circuit 3 and sent to a wavelength filter 2. The transmission characteristic of the wavelength filter 2 has sufficient narrow band block characteristics in comparison with the spectrum of the optical signal and a block central wavelength is controlled corresponding to the sub signal. As a result, the sub signal is multiplexed with a component λ1, for example, of the main signal and sent to a transmission line 4. The transmitted signal is split into two by a beam splitting circuit 5. One signal is converted to a digitized main signal and the other signal is converted to a digitized sub signal after only the component λ1 is extracted by a filter 8 passing wavelength λ1. |
