A Fiber-Transmission-Assisted Fast Digital Self-Interference Cancellation for Overcoming Multipath Effect and Nonlinear Distortion

Self-interference (SI) influenced the recovery of the signal of interest (SOI) in In Band Full Duplex (IBFD) radio-over-fiber (ROF) links. The multipath effect and nonlinear distortion aggravate the difficulty of the SI signal elimination. A fiber-transmission-assisted digital self-interference cancellation (DSIC) scheme is proposed to solve the problem at a low time complexity. The key to removing the impact of harmful factors is combined with the advantages of photonics architecture and digital filter algorithm. A fiber-transmission-assisted scheme achieves the transmission of reference signals with all the linear and nonlinear features which transform the nonlinear problem into a linear question for DSIC subsequently. In DSIC, a fast transversal recursive least-squares (FTRLS) algorithm realizes a fast-channel estimating process when the SOI is involved. For 10 km fiber transmission, exceeding 38 dB and 34 dB cancellation depth over 50 MHz bandwidth in the X band and Ku band are experimentally demonstrated, and 25 Mbaud 16-quadrature amplitude modulation (16-QAM) SOI is successfully recovered after SIC. In addition, FTRLS merely consumed 7N + 14 multiplication times at each iteration (filter order N) in the channel estimating process, which saves multiplications amount above 86% than RLS, DNN, Volterra-RLS algorithm, when N is equal to 80.