Multispectral Sampling Sequence Formation in an Analog Optical Path: Possibility of Automatic Control Using Digital Feedback

In this study, we discuss the application of high-stability, pulsed mode-locked lasers (MLLs) as sources of sampling signals with low jitter in wide-bandwidth, photonic analog-to-digital converters. The implementation of a promising method of increasing the sampling rate of signals with bandwidth up to 2 GHz requires systems with multispectral, repetitively pulsed sampling sequences. On account of the sensitivity of such systems to temperature changes and mechanical disturbances, the jitter of the sampling sequences increases and errors in setting the light-signal delays in the spectral channels result in the violation of pulse-repetition equidistance. Consequently, such a degradation of sampling-sequence quality decreases analog-to-digital conversion precision. The method of processing automatic control of an analog optical path using digital feedback and motorized delay lines is proposed for sampling multispectral sequence pulses equidistance improvement. The results of mathematical modeling and experimental implementation of the method in a 3-channel sampling multispectral sequence generation system with tripling of the pulses rate of the source MLL are presented. The discussed method can be applied in constructing optical sampling-based, analog-to-digital microwave photonic systems for different purposes.