Abstract
Low-loss dispersive components are critical to photonic time-stretch
analog-to-digital converters (TS-ADCs) for attaining high resolutions. Chirped
fiber-Bragg gratings (CFBGs) provide low losses plus high nonlinear thresholds
but introduce time-warp and intensity-modulation distortions from group-delay
ripple (GDR). Practical signal processing routines to mitigate GDR distortions
are assessed for the two fundamental TS-ADC differential architectures. For
differential TS-ADCs that use a common time-stretching element, differential
RF extraction together with time-stretch linearization provides effective
GDR mitigation. For differential TS-ADCs that use separate time-stretching
elements, intensity scale factors proportional to the reciprocal of the GDR-induced
intensity modulation are first applied, or alternatively DC-offset subtraction
can provide effective mitigation when the separate path losses are sufficiently
balanced. Using pulse propagation siμlations with actual CFBG GDR data, these
routines are projected to mitigate CFBG GDR distortions to levels commensurate
with >11
effective resolution bits for input RF bandwidths of at least 0-to-10 GHz
and time-stretch factors >10.
© 2013 IEEE
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