Ultra Wideband Measurement for Arbitrary Spectral Response Using Double Sideband Modulation and Low-Frequency Detection

An ultra-wideband measurement for arbitrary optical magnitude response is proposed and experimentally demonstrated by using optical carrier-suppressed double sideband modulation and fixed low-frequency detection. Compared with previous optical single sideband modulation-based methods, the proposed scheme doubles the measurement range. Moreover, the response can be detected at a fixed low frequency by incorporating microwave photonic frequency down-conversion. The proposed approach has the merit of measuring arbitrary response avoiding high-speed and wideband detectors. To verify the concept, simulation and experiment are carried out. The magnitude responses of two fiber Bragg gratings, which have bandwidths of 19.8 GHz and 67 GHz, are characterized with a resolution of 10 MHz by using a 43.5 GHz microwave signal source.