Adaptive optical self-interference cancellation using a semiconductor optical amplifier

We experimentally demonstrate an optical system that uses a semiconductor optical amplifier (SOA) to perform adaptive, analog self-interference cancellation for radio-frequency signals. The system subtracts a known interference signal from a corrupted received signal to recover a weak signal of interest. The SOA uses a combination of slow and fast light and cross-gain modulation to perform precise amplitude and phase matching to cancel the interference. The system achieves 38 dB of cancellation across 60-MHz instantaneous bandwidth and 56 dB of narrowband cancellation, limited by noise. The Nelder-Mead simplex algorithm is used to adaptively minimize the interference power through the control of the semiconductor's bias current and input optical power.