Optical frequency comb based coherent phase recovery simplification
Coherent phase recovery method includes producing, with a transmit-side frequency-comb source, a first frequency-comb signal that includes a pilot tone and a first optical tone having a first center wavelength that differs from a pilot center wavelength of the pilot tone. The method also includes coherently modulating the first optical tone to yield a first modulated signal; and generating a second frequency-comb signal with a receive-side frequency-comb source driven by the pilot tone. The method also includes extracting, from the second frequency-comb signal, a first local-oscillator tone having the first center wavelength; and demodulating the first modulated signal by homodyning the first modulated signal with the first local-oscillator tone.
1 . A coherent phase recovery method, the method comprising:
producing, with a transmit-side frequency-comb source, a first frequency-comb signal that includes a pilot tone and a first optical tone having a first center wavelength that differs from a pilot center wavelength of the pilot tone;
coherently modulating the first optical tone to yield a first modulated signal;
generating a second frequency-comb signal with a receive-side frequency-comb source driven by the pilot tone;
extracting, from the second frequency-comb signal, a first local-oscillator tone having the first center wavelength;
demodulating the first modulated signal using the first local-oscillator tone to obtain a first demodulated signal;
generating a pilot beat signal from the pilot tone with a pilot-tone receiver; and
determining a noise-corrected phase signal from a difference between the first demodulated signal and the pilot beat signal.
2 . The method of claim 1 , the first frequency-comb signal further including a second optical tone having a second center wavelength that differs from each of the first center wavelength and the pilot center wavelength, and the method further comprising:
coherently modulating the second optical tone to yield a second modulated signal;
extracting, from the second frequency-comb signal, a second local-oscillator tone having the second center wavelength; and
demodulating the second modulated signal using the second local-oscillator tone.
3 . The method of claim 2 , wherein demodulating the second modulated signal using the second local-oscillator tone comprises demodulating the second modulated signal by homodyning the second modulated signal with the second local-oscillator tone.
4 . The method of claim 1 , wherein extracting, from the second frequency-comb signal, the first local-oscillator tone comprises demultiplexing the second frequency-comb signal to produce a plurality of local-oscillator tones that includes the first local-oscillator tone.
5 . The method of claim 1 , wherein demodulating the first modulated signal using the first local-oscillator tone comprises demodulating the first modulated signal by homodyning the first modulated signal with the first local-oscillator tone.
6 . A coherent phase recovery system, comprising:
a first frequency-comb source including a transmit-side comb-output port and being configured to generate a first frequency-comb signal that includes a pilot tone and a first optical tone;
a first signal divider having (i) a first common port optically coupled to the transmit-side comb-output port, (ii) a first pilot port configured to output the pilot tone, and (iii) a first non-pilot port configured to output the first optical tone;
a coherent modulator having (i) an input port optically coupled to the first non-pilot port and (ii) a modulator-output port;
a signal combiner having (i) a second pilot port optically coupled to the first pilot port, (ii) a second non-pilot port optically coupled to the modulator-output port, and (iii) a second common port;
a second signal divider having (i) a third common port optically coupled to the second common port, (ii) a third pilot port configured to output the pilot tone, and (iii) a third non-pilot port configured to output the first optical tone;
a coherent receiver having a modulated-signal port optically coupled to the third non-pilot port;
a pilot-tone receiver having an input port optically coupled to the third pilot port;
a second frequency-comb source configured to generate a second frequency-comb signal from an output of the third pilot port of the second signal divider;
a third signal divider configured to extract, from the second frequency-comb signal, a first local-oscillator tone for use by the coherent receiver; and
a signal processor communicatively coupled to each of (i) the output of the pilot-tone receiver and (ii) an output port of the coherent receiver, the signal processor being configured to determine a noise-corrected phase signal from a difference between a demodulated signal from the output port of the coherent receiver and a pilot beat signal from the output of pilot-tone receiver.
7 . The system of claim 6 , further comprising an optical fiber link communicatively coupling the second common port and the third common port.
8 . The system of claim 6 , further comprising a polarization controller optically coupled to the third pilot port of the second signal divider.
9 . The system of claim 6 , further comprising an amplifier optically coupled between the third pilot port of the second signal divider and the second frequency-comb source.
10 . A coherent phase recovery system, comprising:
a receive-side frequency-comb source having a comb-input port and a first comb-output port;
a coherent receiver having a local-oscillator port, a modulated-signal port, and an output port;
a first signal divider having a first common port optically coupled to the first comb-output port, and a local-oscillator output port optically coupled to the local-oscillator port;
a second signal divider having (i) a pilot port optically coupled to the comb-input port, and (ii) a non-pilot port optically coupled to the modulated-signal port of the coherent receiver;
a pilot-tone receiver communicatively coupled to the pilot port of the second signal divider; and
a signal processor communicatively coupled to each of (i) an output port of the pilot-tone receiver and (ii) the output port of the coherent receiver, the signal processor being configured to determine a noise-corrected phase signal from a difference between a demodulated signal from the output port of the coherent receiver and a pilot beat signal from the output port of pilot-tone receiver.
11 . The system of claim 10 , the first signal divider being one of a demultiplexer and a wavelength-selective switch, and the second signal divider being one of a demultiplexer and a wavelength-selective switch.
12 . The system of claim 10 , further comprising:
a signal combiner having a common combiner-port optically coupled to a second common port of the second signal divider;
a transmit-side frequency-comb source configured to generate a frequency-comb signal having a frequency-comb spectrum that includes a pilot tone and a first optical tone; and
a transmit-side signal divider having (i) a transmit-side multiplexed port optically coupled to a transmit-side comb-output port of the transmit-side frequency-comb source, (ii) a pilot demultiplexed port optically coupled to the transmit-side multiplexed port and configured to output the pilot tone, and (iii) a non-pilot multiplexed port optically coupled to the transmit-side multiplexed port and configured to output the first optical tone.
13 . The system of claim 12 ,
the second signal divider being a demultiplexer;
the signal combiner being a multiplexer; and
the transmit-side signal divider being one of a wavelength-selective switch and a demultiplexer.
14 . The system of claim 12 , further comprising a coherent modulator having (i) an input port optically coupled to the non-pilot multiplexed port and (ii) an output port optically coupled to the signal combiner.
15 . The system of claim 12 , further comprising an optical fiber link communicatively coupling the common combiner-port to the second common port of the second signal divider.
16 . The system of claim 12 , further comprising an amplifier optically coupled between the pilot demultiplexed port and the signal combiner.
17 . The system of claim 10 , further comprising a polarization controller optically coupled between the pilot port of the second signal divider and the comb-input port.
18 . The system of claim 10 , the pilot port being configured to output a pilot tone having a pilot center wavelength, and the non-pilot port being configured to output a first optical tone having a first center wavelength that differs from the pilot center wavelength.
19 . The system of claim 10 , further comprising further comprising an amplifier optically coupled between the pilot port of the second signal divider and the comb-input port.