An adaptive delay calibration method for optical beamforming networks based on wideband sweep and windowed FFT spectrum analysis

An adaptive delay calibration method for optical beamforming networks (OBFN) based on wideband sweep and windowed FFT spectrum analysis is proposed and demonstrated by simulation. With the FFT spectrum analysis of the wideband sweep signal, the delay difference between different channels in OBFN can be obtained continuously, and can be canceled adaptively by controlling variable optical delay lines(VODL), resulting in fast and high precision calibration for an OBFN. Furthermore, assisted by pilot carriers with multiple frequencies, the phase unwrapping can be achieved, and phase difference beyond 2π can be compensated. In order to demonstrate such method, a 16-arrayoptical beamforming simulation system is presented in this paper. Simulation results show that delay calibration range reaches467.1ps with the frequency range of 6-18 GHz. The delay calibration accuracy is increased by 50 times from5ps to 0.1ps. In addition, the number of simultaneous beamformer achieves to be 3, which covers the airspace from-30° to +30°.