Title :
Distortion Cancellation in Time-Stretch Analog-to-Digital Converter
Author :
Gupta, Shalabh ; Valley, George C. ; Jalali, Bahram
Author_Institution :
California Univ., Los Angeles
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.
Keywords :
Mach-Zehnder interferometers; analogue-digital conversion; electro-optical modulation; optical communication; optical fibre dispersion; differential operation; distortion cancellation; electronic digitizer; electrooptic modulation; optical communication; optical fiber dispersion; push-pull Mach-Zehnder modulator; signal harmonics; signal processing; signal-to-noise ratio; time-stretch analog-to-digital converter; Analog-digital conversion; Digital signal processing; Dynamic range; Nonlinear distortion; Predictive models; Robustness; Signal generators; Signal processing; Signal to noise ratio; Ultra wideband technology; Analog-to-digital conversion; electrooptic modulation; nonlinear distortion; optical communication; optical fiber dispersion;
Journal_Title :
Lightwave Technology, Journal of
DOI :
10.1109/JLT.2007.909343
