Feedforward linearization for RF photonic link with broadband adjustment-free operation.

Linearization of radio frequency (RF) photonic link is critical for advance applications because a nonlinear transfer function of electro-optic modulation limits link dynamic range. Although numerous approaches to suppress third order intermodulation distortion (IMD3) have been demonstrated in previous literatures, many schemes need attendant link optimization when an input RF carrier frequency is tuned over a broad band. In this paper, we propose and demonstrate an adjustment-free linearization approach where high dynamic range could be kept during RF frequency tuning. After a regular low-biased external modulation, the "distortion information" is extracted by a baseband receiver, which then modulates the optically-carried RF signal again. Such distortion extraction and correction is baseband and is independent on the frequency of the RF frequency. The proposal is theoretically analyzed and simulated. In an experiment, IMD3 nonlinear spurs are suppressed over around 60 dB uniformly under typical input RF power, while the carrier is tuned from 4 GHz to 12 GHz. The spurious-free dynamic range (SFDR) is kept around 125 dB within 1-Hz bandwidth without attendant optimization of link parameters.