Reference frequencies comb generation for microwave photonics ADC with signal spectral-interval estimation

Abstract

Formation of a reference frequency comb in a circuit comprising a highly stable continuous laser and an amplitude Mach- Zehnder modulator with two independent RF inputs working with large modulation index for use in a high-speed microwave photonics ADC with spectral-interval estimation is investigated by numerical simulation. In such ADCs, the entire spectrum of the input signal is divided by microwave photonics elements into spectral intervals, each of which uses a microwave photonics converter to transform the signal to an intermediate frequency (for each part of the spectrum of the microwave input signal, its own reference frequency is used for heterodyning). The requirements for a multimode source of optical reference frequencies for high-speed microwave photonics ADC are formulated. To study the characteristics of such a source, numerical modeling is carried out. It is shown that the frequency noise of the laser can be partially suppressed due to their compensation when converted to an intermediate frequency. Experimental study of the reference frequency comb generator layout showed a good agreement of the obtained characteristics with the results of numerical simulation.