A monitoring system has the capability to monitor multiple signal bands simultaneously. Specifically, in one embodiment, the monitoring system can simultaneously monitor the C- and L-bands. As a result, the time to scan through the spectral band can be reduced by half. The system comprises a signal source for an optical signal having spectrally separated channels distributed within a first spectral band and a second spectral band. A tunable filter filters this optical signal. A dichroic filter separates the first spectral band from the second spectral band in the optical signal, which has been filtered by the tunable filter. Thereafter, first and second optical detectors detect the respective spectral bands to the filtered optical signal.