A fifth-order polynomial predistortion circuit for Mach-Zehnder modulator linearization in 65nm CMOS

Future RF photonic systems offer the promise of wideband front-end operation, but are limited by linearity in the electrical-to-optical conversion process. This paper presents a fifth-order polynomial predistortion circuit for optical Mach-Zehnder modulator linearization. Inclusion of independently tunable polynomial coefficients provides the flexibility to suppress both third-order (IM3) and fifth-order (IM5) intermodulation products. Fabricated in 65nm CMOS, the predistortion circuit achieves a measured IM3 suppression of 19.5dB and 17.1dB with modulation indexes of 49.6% and 60%, respectively.