Performance Improvement of Frequency-Domain Light Intensity Spectrum Analyzer (f-LISA)

Ultrafast measurement ofbroadband radio frequency (RF) spectrum is of great importance in dispersion compensation, signal impairment monitoring and coherence analysis. As an all-optical RF spectrum measuring system, the frequency-domain light intensity spectrum analyzer ( f -LISA) maps the RF information into the time domain and realizes the single-shot RF spectrum acquisition. In order to further improve the performance of f -LISA, we investigate theoretically the relationship of resolution and bandwidth with the factors including the spectral width of the probe, the front and output 3 rd -order dispersion (TOD). Under the theoretical guidance, 1 nm spectral width of the probe is filtered out to reduce the impact of the front TOD, and the optical phase conjugation is adopted to decrease the output TOD which has a greater impact on f -LISA. The optimized f -LISA achieves the frame rate of 20.6 MHz, the resolution of 1 GHz and the bandwidth of 2.2 THz which is 3 times wider than the original f -LISA, demonstrating better measurement stability and accuracy. Furthermore, the high-speed and broadband RF spectrum analyzer is promising to provide a solution for ultrafast dynamical RF spectrum scenario like terahertz measurement.