Patent ID: 7941054
Filing Date: 2011-05-10
Classification: H04L

Abstract:
1. A clock signal extraction system comprising: an optical modulator that intensity-modulates an input optical signal outside with a modulation electrical signal, outputting a modulated optical pulse signal, the input optical signal having a clock frequency substantially equal to a predetermined first frequency or a predetermined second frequency different from the predetermined first frequency, the modulation electrical signal having a modulation frequency of an average of the predetermined first and second frequencies; a reference signal generator that generates a reference electrical signal at a reference frequency; a phase comparator that compares in phase the modulated optical pulse signal with the reference electrical signal, and outputs a comparison result as a phase comparison signal; a modulation electrical signal generator that receives the phase comparison signal, and outputs the modulation electrical signal; and a clock signal generator that mixes the modulation electrical signal with the reference electrical signal, generates a combined signal, filters the combined signal, and outputs the filtered signal as a clock signal.