Digital suppression of both cross and inter-modulation distortion in multi-carrier RF photonic link with down-conversion

We propose and demonstrate a novel scheme to effectively suppress the cross modulation distortion (XMD) and the third-order inter-modulation distortion (IMD3) which exist in wide-band, multi-carrier analog photonic link (APL) system. Such nonlinearities, which are caused by the out-of-band and in-band signals, respectively, constrain the link's performance severely. Instead of building an extra nonlinear path in hardware, the XMD and IMD3 compensation information is extracted from the received distorted signal, and both distortions are then suppressed by digitally multiplying the distorted signal with the compensation information. After compensation in the digital domain, the down-converted XMD and IMD3 distortions are experimentally suppressed with 33 dB and 25 dB, respectively, resulting in an improved upper limit for the SFDR.