Enhanced sensitivity in WDM optical monitoring using a MARS optical chopper

A MARS optical chopper is implemented with lock-in detection to enhance the sensitivity of a 1550-nm band wavelength-division multiplexing (WDM) optical monitor and improve its immunity of 1/f noise and dc drift. The high chopping rate, 1.02 MHz, it ideally suited for rapid-scanning optical monitors, allowing <100 /spl mu/s filter time constants for high-rate data acquisition.