Orthogonal frequency-division multiplexing (OFDM) has a high peak-to-average ratio (PAR), which can result in low optical power efficiency when modulated through a Mach–Zehnder (MZ) modulator. In addition, the nonlinear characteristic of the MZ can cause significant distortion on the OFDM signal, leading to in-band intermodulation products between subcarriers. We show that a quadrature MZ with digital predistortion and hard clipping is able to overcome the previous impairments. We consider quantization noise and compute the minimum number of bits required in the digital-to-analog converter (D/A). Finally, we discuss a dual-drive MZ as a simpler alternative for the OFDM modulator, but our results show that it requires a higher oversampling ratio to achieve the same performance as the quadrature MZ.
© 2009 IEEE
Daniel J. Fernandes Barros and Joseph M. Kahn, "Optical Modulator Optimization for Orthogonal Frequency-Division Multiplexing," J. Lightwave Technol. 27, 2370-2378 (2009)