Enhanced Spurious-Free Dynamic Range in Intensity-Modulated Analog Photonic Link Using Digital Postprocessing

In this paper, a post digital linearization technique is proposed and demonstrated for a conventional intensity-modulation direct-detection analog photonic link. Instead of precisely emulating the transfer function of the whole nonlinear system in the digital domain, the key distortion information is directly acquired from hardware. By low biasing the Mach-Zehnder modulator, linearization can be achieved through simply multiplying the distorted signal by the coreceived low-pass band. Theory analysis shows that only the bias angle should be known by the algorithm, whereas the simulation shows adequate tolerance. The low bias angle also results in an improved link gain. The experiment shows a well-suppressed third-order intermodulation distortion (IMD3). With the optical down conversion, we demonstrate a spurious-free dynamic range increasing from 103.2 to 123.3 dB in a 1-Hz bandwidth.