| 摘要 |
PURPOSE:To measure nonlinear distortion of an optical receiver unit, by coupling a video test signal for linearity measurement eliminating chrominance subcarrier outputted respectively from two optical transmitters with a chrominance subcarrier, and synthesizing an optical DG/DP measuring signal. CONSTITUTION:The chrominance subcarrier is rejeced from a linearity measuring video test signal 2 outputted from a DG/DP measuring signal generator 10 at a low- pass filter 11, and a linearity measuring optical test signal 12 rejecting chrominance signal is transmitted with an optical transmitter 5a. On the other hand, a chrominance subcarrier 13 is outputted from the signal generator 10, and an optical signal 15 subjected to intensity modulation with the chrominance subcarrier is transmitted with an optical transmitter 5b through a level adjuster 14. The signals 12, 15 are coupled at an photocoupler 16 to synthesize an optical DG/DP measuring signal 17. Further, the measuring signal 17 in a specified level is inputted to an optical receiver 6 and the electric output of the optical receiver 6 is measured at a DG/DP measuring device 4, allowing to measure nonlinear distortion of the optical receiver 6. |
