US 2003/0118349 A1Published application

Optical clock phase-locked loop circuit

AssigneeNippon Telegraph and Telephone Corporation

InventorsTakuya Ohara, Hidehiko Takara, Satoki Kawanishi

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Abstract

This optical clock phase-locked loop circuit includes an oscillator 12, an optical coupler 2, an optical cross-correlation detection device 3 that outputs light containing the correlating components of two lights from the coupled light of optical coupler 2, an optical band pass filter 4 that extracts light of a wavelength that contains cross-correlating components, an optical receiver 5, a phase comparator 6 that compares the phases of the output signal of the oscillator 12 and the cross-correlation signal from the optical receiver 5, a voltage controlled oscillator 7 that changes the oscillation frequency and phase corresponding to the output of the phase comparator 6, an optical pulse generator 8 that generates a optical clock pulse containing an nth harmonic component, an optical coupler 10 that divides optical clock, and an optical modulator 11 driven by low-frequency oscillator 12 that modulates optical clock from optical coupler 10.

Claims12

Dependent claims

An optical clock phase-locked loop circuit comprising:

a first oscillator that outputs an alternating current signal,
a first optical coupler that couples input optical signal and modulated optical clock,
an optical cross-correlation detection device that incorporates optical signal and modulated optical clock coupled by the first optical coupler, and outputs light that contains the cross-correlation components between both lights,
an optical band pass filter that extracts light of a wavelength that contains cross-correlating components from the output from the optical cross-correlation detection device,
an optical receiver that converts a light containing cross-correlating components extracted with the optical band pass filter to an electric signal,
a phase comparator that compares the phases of the output signal of the first oscillator and the cross-correlation signal output from the optical receiver,
a second oscillator that changes the oscillation frequency and phase corresponding to the output of the phase comparator,
an optical pulse generator driven by the second oscillator that generates optical clock having a narrow enough pulse width for containing an nth harmonic component (where n is an integer of 2 or more),
a second optical coupler that divides into two portions the optical clock output from the optical pulse generator,
an optical modulator driven by the first oscillator that modulates one portion of the optical clock divided by the second optical coupler, and outputs that portion in the form of the modulated optical clock to the first optical coupler, and
an output device that outputs the other portion of the optical clock divided by the second optical coupler.

8 more elements

An optical clock phase-locked loop circuit comprising:

a first oscillator that outputs an alternating current signal,
a first optical coupler that couples input optical signal and modulated optical clock,
an optical cross-correlation detection device that incorporates optical signal coupled by the first optical coupler and modulated optical clock, and outputs light that contains the cross-correlation components between both lights,
an optical band pass filter that extracts light of a wavelength that contains cross-correlating components from the output from the optical cross-correlation detection device,
an optical receiver that converts a light containing cross-correlating components extracted with the optical band pass filter to an electric signal,
a phase comparator that composes the phases of the output signal of the first oscillator and the cross-correlation signal output from the optical receiver,
a second oscillator that changes the oscillation frequency and phase corresponding to the output of the phase comparator,
an optical pulse generator driven by the second oscillator that generates an optical pulse train at a repetition frequency n times (where n is an integer of 2 or more) the oscillation frequency of said second oscillator,
a second optical coupler that divides into two portions the optical clock output from the optical pulse generator,
an optical modulator driven by the first oscillator that modulates one portion of the optical clock divided by the second optical coupler, and outputs that portion in the form of the modulated optical clock to the first optical coupler, and
an output device that outputs the other portion of the optical clock divided by the second optical coupler.

8 more elements

Dependencies are inferred from the claim text.