Opto-Electronic Clock Regeneration -- A Tutorial

TL;DR

This tutorial explains opto-electronic clock regeneration at very high bit rates using nonlinear materials and phase-locked loops, highlighting the design and operation of an opto-electronic PLL with sum frequency generation.

Contribution

It provides a comprehensive tutorial on implementing opto-electronic clock recovery with nonlinear materials and phase-locked loops for high-speed applications.

Findings

Effective opto-electronic clock recovery at high bit rates.

Use of LiNbO3 for sum frequency generation in clock regeneration.

Design of an OPLL with integrated phase comparator and VCO.

Abstract

A tutorial on opto-electronic clock regeneration at very high bit rates beyond reach with purely electronic solutions is given. Emphasis is placed on sum frequency generation in a nonlinear material such as LiNbO3. We first provide a basic introduction to CR (clock recovery) and a PLL (phase-locked loop); two examples are considered, an input signal frequency step and a slow input signal frequency. Next we discuss opto-electronic clock recovery based on an OPLL (opto-electronic PLL). The OPLL contains a phase comparator consisting of a planar LiNbO3 waveguide, a lowpass filter, a VCO (voltage controlled oscillator) and a local oscillator laser. The error signal from the comparator determined by the difference in electrical phase between the signal and the VCO controls the VCO. The VCO has two outputs; one that modulates the local oscillator laser and another that triggers a decision circuit that samples the output from the OPLL. The VCO is continuously adjusted by the OPLL so that it will ensure sampling of the signal in the optimal moments.