To prevent a spurious disturbance wave and second distortion due to unnecessary band signal in a signal processing system.

An incoming optical signal corresponds to the synthetic signal of an FM luminance signal YFM and an FM chrominance signal CFM. The optical signal is converted to an electric signal by a photodiode 401 and this electric signal is supplied for a preamplifier 403 through a filter 402 removing the FM chrominance signal CFM of 20 to 30MHz. On the other hand, the optical signal is converted to an electric signal by a photodiode 421 and this electric signal is supplied for a preamplifier 423 through a filter 422 removing the FM luminance signal YFM of 6 to 20MHz. Since only the signal YFM is amplified by the preamplifier 403, a spurious disturbance wave due to the signals YFM and CFM is not generated in the band of the signal Y though the preamplifier 403 is provided with a nonlinear characteristic. Since only the signal CFM is amplified by the preamplifier 423 on the other hand, the second distortion of the signal YFM is not generated in the band of the signal CFM though the preamplifier 423 is provided with a nonlinear characteristic.