Dynamic range improvement in analog photonic link by intermodulation-compensation receiver.

In this paper, a novel intermodulation-compensation optical receiver based on the bias-modulated photo detector (PD) is proposed and demonstrated to eliminate the third-order intermodulation (IMD3) for the intensity-modulation direct-detection (IMDD) analog photonic link. We directly extract the key nonlinear distortion from the distorted optical intensity by a low-pass optical receiver, which is used to modulate the home-made, high-speed PD with bias modulation. Inside the high speed PD, the distorted radio frequency (RF) band is mixed with the above extracted baseband signal, and the IMD3 elimination can be achieved. Our proposal is theoretically analyzed, and the performance of the bias-modulated PD is experimentally demonstrated. Spurious-free dynamic range (SFDR) of 123.4 dB within 1-Hz bandwidth is obtained with 18.1 dB improvement. A low-biased Mach-Zehnder modulator (MZM) is used, keeping a simple transmitter with an improved link gain. The proposed post linearization requires no digital processing, avoiding the high quantization noise.