Optical signal monitor for multiwave optical signals

In accordance with the present invention, apparatus for and method of operating an optical signal monitor is disclosed for providing rapid monitoring of optical signals using a high speed optical modulator. One illustrative optical signal monitor includes (1) a Mechanical AntiReflective Switch (MARS) optical modulator (signal chopper) capable of operating at 10 MHz rates and having a detection bandwidth greater than 100 kHz and (2) a synchronous detector using lock-in detection in a 1550 nm-band WDM optical monitor to enhance detection sensitivity by greater than 30 dB compared to direction detection methods. According to another embodiment, the optical monitor can be used to control adaptive optical amplifier units or equalizer units of a wavelength division multiplexed (WDM) system.