Abstract
We show that the symmetry properties of the two outputs from a push–pull Mach–Zehnder modulator
can be exploited to reject dispersion-induced second-order distortions in the time-stretch analog-to-digital
converter (TS-ADC). Using differential operation and signal processing in the digital domain, we experimentally
demonstrate suppression of the signal harmonics generated due to system nonlinearities. Simulations predict that
distortion-limited dynamic range improves from 34 to 57 dB. In addition, differential signaling improves the
signal-to-noise ratio (SNR) by 3 dB and rejects an even-order nonlinear distortion added by an electronic digitizer
in the TS-ADC. It is also shown that this approach is robust even in the presence of mismatches in the differential
signal paths. In general, the approach can also be applied to any ultrawideband (multioctave) optical link to obtain
a high dynamic-range system.
© 2007 IEEE
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