Abstract
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
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