A switchable self-interference cancellation system for dual-band IBFD system using a monolithic integrated DML array

Abstract

A dual-band optical self-interference cancellation (OSIC) system is proposed and experimentally demonstrated for in-band full-duplex (IBFD) system using a monolithic integrated multi-channel directly modulated laser (DML) array, tunable optical delay line (TODL) and optical variation attenuator (OVA), and photodetector. The key component of the OSIC system is the integrated DML array which is measured in terms of the spectral characteristic, P–I curve, and small-signal frequency response. The use of the integrated DML array can greatly save the cost as well as reduce the complexity and power consumption of the system. The proposed system is theoretically and experimentally verified. The theoretical analysis shows that the cancellation depth is associated with the attenuation ratio, the time delay and the microwave frequency of the RF signal. Experimentally, the cancellation depth is more than 43 dB in the frequency of 2.4 GHz and 5 GHz. For a broadband RF signal, cancellation depth of 25 dB is achieved with the bandwidth of ∼260 MHz at a center frequency of 2.4 GHz and 5 GHz. In addition, the switchability between double frequencies of the applied microwave signal makes the OSIC system more flexible and fast without adjusting the TODL and OVA, repeatedly