Dynamic-Range Enhancement for a Microwave Photonic Link Based on a Polarization Modulator

A microwave photonic link (MPL) with an increased spurious-free dynamic range (SFDR) using a polarization modulator is proposed and experimentally demonstrated. The fundamental concept of the proposed approach to increase the SFDR is to reduce the third-order intermodulation distortion (IMD3) and to improve the modulation efficiency by partial carrier suppression, which is realized here by producing two channels of intensity-modulated signals with one having only the upper sidebands and the other having the optical carrier that is partially suppressed and the upper sidebands using two optical filters. If the optical powers into the two channels are kept identical, the combination of the two signals at a photodetector will fully cancel the IMD3 terms. In addition, the modulation efficiency is optimized due to the partial carrier suppression, which also leads to an increased SFDR. The proposed MPL is theoretically studied and experimentally demonstrated. An SFDR of 123.48 dB.Hz(2/3) at a noise floor of -166 dBm/Hz is achieved, which is 15 dB higher than that of a regular intensity-modulation and direct-detection MPL.