Heterodyne Method for Time Resolved Spectral Analysis of Fast Laser Wavelength Switching

We present a highly sensitive heterodyne method for time resolved optical spectrum analysis of fast laser wavelength switching. The method achieves signal-to-noise ratios in excess of 50 dB and allows, for the first time, the direct measurement of the dynamic sidemode suppression ratio during fast laser channel transitions. Wavelength range and accuracy are determined by the reference external cavity laser, while temporal and wavelength resolution are set by electronic filtering.