Photonic-assisted multi-frequency measurement based on frequency-to-power mapping and serial channelization

A novel photonic approach to multi-frequency measurement based on frequency-to-power mapping and serial channelization is proposed and demonstrated. In this proposal, a light wave from a laser diode (LD) is split into two branches. In the upper branch, a dual-port Mach–Zehnder interferometer (MZI) is used to perform frequency-to-power mapping. While in the lower branch, an optical wavelength scanner based recirculating frequency shifting (RFS) loop is used to generate multiple serial optical local oscillators (LOs) to down-convert the outputs of the dual-port MZI at the corresponding time window. Therefore, the unknown radio-frequency (RF) frequencies can be unambiguously estimated by the multiple monotonous amplitude comparison functions (ACFs) obtained from the power ratios between two down-converted electrical signals. Only two low-frequency photodetectors (PDs) with narrow bandwidth are employed, which guarantees a simple structure and low cost. In addition, the proposal has robustness to the bias drift of the MZM and input RF power. Simulation results indicate that the multi-frequency identification within 5 μs is achieved over the measurement range up to 19 GHz with an accuracy better than ± 20 MHz. Furthermore, the system is easily extended to higher frequency and larger bandwidth (e.g., 100 GHz).