Wideband Reconfigurable Instantaneous Microwave Multi-frequency Measurement System Based on an Optical Frequency Shifter and Optical Frequency Comb

In this paper, a wideband reconfigurable instantaneous microwave multifrequency measurement system based on an optical frequency shifter and optical frequency comb has been proposed, designed and investigated. In the scheme, an optical frequency shift is employed to shift the optical carrier of the input dual-parallel Mach-Zehnder modulator (DPMZM) and align it with the first comb line of the optical frequency comb. Simultaneously, the central frequencies of the two demultiplexers are designed so that the output of 90 degrees optical hybrid coupler contains only one local oscillator optical carrier. Furthermore, the local oscillator optical carrier is positioned at the initial location of the channel. The issue of frequency ambiguity caused by the beating frequencies generated between the unknown signal and a pair of different power local oscillator carriers is resolved by combining a 90 degrees OHC and a pair of balanced photodetectors (BPD). Simulation results reveal that when the channel bandwidth is set to 2 GHz, the system frequency measurement range is 0.01-50 GHz, with an error of less than +/- 5 MHz. By adjusting the channel bandwidth to 4 GHz, the system measurement range is 0.01-100 GHz, with a frequency measurement error of 5-14.6 MHz. This approach offers advantages such as a wide measurement range, reconfigurability, and low error.