| 摘要 |
An optical filter performs filtering on input monitor light in a transmission range having a carrier frequency of each channel being measured as a center frequency. Photoelectric convertors convert the monitor light filtered by the optical filter into an electrical monitor signal, and the signal detection unit judges whether signal light is present or absent based on the electrical monitor signal. Since the optical filter performs filtering, an S/N ratio of the monitor light becomes great and the signal detection unit can more accurately judge whether signal light is present or absent even in an optically noisy environment. |
