For monitoring high-speed optical telecom signals and/or spectrally broadened light waves, such as optical frequency combs, it is desired to measure the optical spectra with higher bandwidth and resolution. For the purposes, in this paper, we demonstrate a high-resolution and high-speed optical spectrum analyzer that only relies on a DSP operated at a much lower speed. This spectrum analyzer consists of two-stage spectroscopy systems, which is a diffractive grating system and a sampled heterodyne system. We experimentally demonstrate the spectral measurement with greater than 10-pm resolution at 100-kHz acquisition rate covering bandwidth of 5-GHz.
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