Chromatic dispersion estimation method for coherent optical network

A method for registering an optical network unit (ONU) with an optical line terminal (OLT), comprising:

• transmitting a register-request-message signal from the ONU to the OLT via an optical-fiber channel to yield a chromatically-dispersed register-request-message signal received by the OLT;
• recovering a grant-message signal of the optical network by:
• (a) detecting, at the ONU, a chromatically-dispersed grant-message signal transmitted from the OLT via the optical-fiber channel and having a symbol rate 1/T;
• (b) estimating an ONU-side chromatic-dispersion estimate of the optical-fiber channel by:
• (i) receiving, via the optical-fiber channel, the chromatically-dispersed grant-message signal;
• (ii) for each chromatic-dispersion value of a plurality of chromatic-dispersion values, determining a respective clock-tone magnitude by:
• applying, to the chromatically-dispersed grant-message signal or a signal derived therefrom, a chromatic dispersion equal to the chromatic-dispersion value to generate a dispersion-compensated signal;
• and
• extracting the clock-tone magnitude from at least one of a positive-frequency clock-tone and a negative-frequency clock-tone of the dispersion-compensated signal, the positive-frequency clock-tone and the negative-frequency clock-tone being spectral components of the dispersion-compensated signal at temporal frequencies 1/T or −1/T respectively;
• and
• (iii) determining a maximum of the extracted clock-tone magnitudes, the estimated chromatic dispersion being the chromatic-dispersion value, of the plurality of chromatic-dispersion values, corresponding to the maximum extracted clock-tone magnitude;
• and
• (c) recovering the grant-message signal from the chromatically-dispersed grant-message signal by applying the ONU-side chromatic-dispersion estimate to the chromatically-dispersed grant-message signal.

A method for registering an optical network unit (ONU) with an optical line terminal (OLT), comprising:

• transmitting a register-request-message signal from the ONU to the OLT via an optical-fiber channel to yield a chromatically-dispersed register-request-message signal received by the OLT and having a symbol rate 1/T;
• generating an OLT-side chromatic-dispersion estimate of the optical-fiber channel by:
• (i) receiving, via the optical-fiber channel, the chromatically-dispersed register-request-message signal;
• (ii) for each chromatic-dispersion value of a plurality of chromatic-dispersion values, determining a respective clock-tone magnitude by:
• applying, to the chromatically-dispersed register-request-message signal, a chromatic dispersion equal to the chromatic-dispersion value to generate a dispersion-compensated signal;
• and
• extracting the clock-tone magnitude from at least one of a positive-frequency clock-tone and a negative-frequency clock-tone of the dispersion-compensated signal, the positive-frequency clock-tone and the negative-frequency clock-tone being spectral components of the dispersion-compensated signal at temporal frequencies 1/T or −1/T respectively;
• and
• determining a maximum of the extracted clock-tone magnitudes, the estimated chromatic dispersion being the chromatic-dispersion value, of the plurality of chromatic-dispersion values, corresponding to the maximum extracted clock-tone magnitude,
• recovering a register-request-message signal from the chromatically-dispersed register-request-message signal by applying the OLT-side chromatic-dispersion estimate to the chromatically-dispersed register-request-message signal.