| 摘要 |
PURPOSE:To reduce the deterioration of the code error rate characteristic caused by distortion of the reception waveform due to the stimulated Brillouin scattering by setting the identification threshold value of the minimum code error rate to an identification circuit based on the intensity of the stimulated Brillouin scattering. CONSTITUTION:A section overhead processing circuit 25 of a light receiving device reads the intensity information on the stimulated Brillouin scattering written at the side of a light transmitting device out of the identification signal received from an identification circuit 24a and gives the read information to a digital signal processing circuit 26a. The circuit 26a stores the relationship between the received intensity information on the stimulated Brillouin scattering and the optimum identification threshold value of the circuit 24a and refers to this relationship to control the identification threshold value in a service mode. Then the circuit 26a changes the intensity of the back dispersion light in response to the stimulated Brillouin scattering caused by changing previously the light transmission level in steps, sweeps the identification threshold value for each intensity information, and measures the optimum identification threshold value that shows the minimum code error rate based on the detection result of a code error detector 68. Thus it is possible to reduce the deterioration of the code error characteristic caused by distortion of the reception waveform due to the stimulated Brillouin scattering. |
