Instantaneous frequency measurement using two parallel I/Q modulators based on optical power monitoring

A scheme for instantaneous frequency measurement (IFM) using two parallel I/Q modulators based on optical power monitoring is proposed. The amplitude comparison function (ACF) can be constructed to establish the relationship between the frequency of radio frequency (RF) signal and the power ratio of two optical signals output by two I/Q modulators. The frequency of RF signal can be derived by measuring the optical power of the optical signals output by two I/Q modulators. The measurement range and measurement error can be adjusted by controlling the delay amount of the electrical delay line. The feasibility of the scheme is verified, and the corresponding measurement range and measurement error of the system under different delay amounts of the electrical delay line are given. Compared with previous IFM schemes, the structure of this scheme is simple. Polarization devices, a photodetector and an electrical power meter are not used, which reduces the impact of the environmental disturbance on the system and the cost of the system. In simulation, the measurement range can reach 0 GHz-24.5 GHz by adjusting the delay amount of the electrical delay line tau = 20 ps. The measurement error of the scheme is better at low frequency, and the measurement error of low frequency 0 GHz-9.6 GHz can reach -0.1 GHz to +0.05 GHz.