Abstract

Because of their potentially much higher operational bandwidths, photonic samplers can provide solutions for the bandwidth limitation of electronic sample and hold circuits [1]. One of these photonic solutions is to sample the signal by a sequence of very short pulses, generated by a mode-locked laser (MLL) [1], for instance. Desktop MLL can have very low jitter. But integrated, low-jitter MLL with a high repetition rate have to be shown yet. Another possibility is orthogonal sampling in a Mach-Zehnder modulator (MZM) [2]. Orthogonal sampling exploits the orthogonality of sinc pulse sequences for a theoretically error-free sampling. In the frequency domain, the orthogonal sampling is the convolution of the signal spectrum with an N-line, phase-locked, flat frequency comb with Δf frequency spacing and a bandwidth of NΔf. This convolution can be directly carried out in an intensity modulator driven with n=(N-1)/2 radio frequencies, generated by a radio oscillator and, the very low jitter even possible with integrated oscillators can be directly transferred to the sampling of the signals. However, for the integration silicon MZM require a quite high chip space and RF power [2]. Silicon ring modulators instead, can be designed much smaller and with less power consumption. In [3] the sampling and thus, convolution with a 3-line comb has been shown.

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