| 摘要 |
PROBLEM TO BE SOLVED: To reproduce a level of an input electric signal at a receiver side, to prevent deterioration in the S/N when a level of the input electric signal is low and to prevent occurrence of distortion when the level of the input electric signal is high. SOLUTION: A level of an input signal 2a is detected by a signal level detection section 22. A transmission level control section 23 sets an amplifier gain of a transmission level variable section 21 in response to a level of the input signal 2a to control the level of an output signal 21a of the transmission level variable section 21 so as to be within a prescribed level range. The output signal 21a whose level is corrected is given to an electrooptic converter 26, where the signal 21a is converted into an optical signal 26a and sent via an optical transmission line 4. The optical transmitter 2 sends a level correction amount applied to the input signal 2a at the transmission level variable section 21 to an optical receiver 3. A reception level variable section 33 of the optical receiver 3 inversely corrects the level of the electric signal outputted from a photoelectric converter 31 based on the level correction amount by the reception level variable section 33 to restore the level to the original level. |
