Optical system and method
First Claim
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1. A method of optical link dispersion compensation, comprising:
- (a) providing a relative phase measurement for an optical link, said phase measurement determined for each wavelength of a set of wavelengths;
(b) using the results of step (a) in computing a first transfer function phase for each of said wavelengths, said first transfer function corresponding to said optical link;
(c) using the results of step (b) in computing an amplitude for said first transfer function; and
(d) applying an optical filter to said optical link, said optical filter with a second transfer function, said second transfer function corresponding to said first transfer function.
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Abstract
Optical network dispersion compensation with adaptive dynamic optical filters which relate magnitude and phase of multichannel optical signals.
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Citations
14 Claims
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1. A method of optical link dispersion compensation, comprising:
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(a) providing a relative phase measurement for an optical link, said phase measurement determined for each wavelength of a set of wavelengths;
(b) using the results of step (a) in computing a first transfer function phase for each of said wavelengths, said first transfer function corresponding to said optical link;
(c) using the results of step (b) in computing an amplitude for said first transfer function; and
(d) applying an optical filter to said optical link, said optical filter with a second transfer function, said second transfer function corresponding to said first transfer function. - View Dependent Claims (2, 3, 4, 7, 12)
(a) said optical filter includes a dispersive element, a plurality of attenuation elements, and a recombining element;
(b) whereby an input signal including said set of wavelengths may be split by said dispersive element into separate signals, and each of said separate signals may be attenuated by a corresponding one of said plurality of attenuation elements, and these attenuated separate signals may be recombined into an output signal by said recombining element.
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3. The method of claim 1, wherein:
(a) said providing a phase measurement of step (a) of claim 1 includes detecting a relative group delay for each of said wavelengths.
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4. The method of claim 1, wherein:
(a) said set of wavelengths are cover wavelengths in a multichannel optical network.
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7. The method of claim 5, wherein:
(a) said providing a phase measurement of step (a) of claim 1 includes detecting a relative group delay for each of said wavelengths.
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12. The procedure of claim 11, further comprising:
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(a) doubling the size of the transform;
(b) inserting zero frequencies in the middle of the transform spectrum to expand the size of the transform; and
(c) repeating procedure of claim 1 for recovering phase, group delay and chromatic dispersion parameters of a system transfer function.
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5. A method of adaptive optical network dispersion compensation, comprising:
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(a) providing a relative phase measurement for each wavelength of a set of wavelengths used in an optical network;
(b) using the results of step (a) in computing a first transfer function phase for each of said wavelengths;
(c) using the results of step (b) in computing an amplitude for said first transfer function;
(d) applying an optical filter in said optical network, said optical filter with a second transfer function, said second transfer function corresponding to said first transfer function; and
(e) repeating steps (a)-(d) to adapt to optical network conditions. - View Dependent Claims (6)
(a) said optical filter includes a dispersive element, a plurality of attenuation elements, and a recombining element;
(b) whereby an input signal including said set of wavelengths may be split by said dispersive element into separate signals, and each of said separate signals may be attenuated by a corresponding one of said plurality of attenuation elements, and these attenuated separate signals may be recombined into an output signal by said recombining element.
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8. A method of optical filter synthesis, comprising:
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(a) providing an amplitude for each of a plurality of wavelengths;
(b) using the results of step (a) in computing a transfer function with magnitude corresponding to said amplitude for said plurality of wavelengths, said computing including complex cepstrum analysis of said magnitude. - View Dependent Claims (9, 10)
(a) zero-padding said magnitude prior to said complex cepstrum analysis.
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10. The method of claim 9, further comprising:
(a) windowing said complex cepstrum prior to discrete Fourier transforming.
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11. A procedure for measuring the chromatic dispersion parameter of a multi-wavelength system transfer function with at least one wavelength from the group delay parameter that is extracted from the phase parameter recovered from measured Intensity data, comprising the following steps:
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(a) measure intensity data to generate magnitude data, said intensity data can be spectral reflectance or transmittance data;
(b) compute logarithmic magnitude data;
(c) perform Inverse Fourier Transform on logarithmic magnitude data;
(d) generate complex cepstrum signal using even function signal property;
(e) optionally perform windowing on the complex cepstrum signal;
(f) reconstruct logarithmic system transfer function by performing a Fourier Transform on (optionally windowed) complex cepstrum signal;
(g) recover magnitude of system transfer function from the Real Part of the Fourier Transform results using the anti-log or exponent function;
(h) recover phase of system transfer function from the Imaginary Part of the Fourier Transform results;
(i) compute the group delay parameter from the recover phase parameter; and
(j) compute the chromatic dispersion parameter from the group delay parameter. - View Dependent Claims (13)
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14. A procedure for specifying the magnitude function of a system transfer function of an optical component for a multi-wavelength system with at least one wavelength given the Chromatic Dispersion parameter of a system transfer function or the Group Delay parameter or the Phase parameter, said procedure for a given or desired Group Delay comprising the following steps to determine both log|H(k)| and φ
- (k) given τ
(k);(a) compute τ
(k) given the desired group delay τ
d(k);
(b) compute pseudo-Cepstral coefficients p(n) via an N-point IDFT of τ
(k);
(c) compute ĥ
p(n) from p(n) as follows;
(d) compute Ĥ
(k) via DFT of ĥ
p(n), the imaginary part of Ĥ
(k) is the unwrapped phase spectrum φ
(k) of the recovered transfer function;
(e) compute log|H(k)| by forming a sequence g(n)=sgn(n).ĥ
(n) for 0≦
n<
N and taking the DFT of g(n);
(f) compute the recovered magnitude function |H(k)| by taking exp[log|H(k)|] where log is the natural logarithm function;
(g) finding the recovered transfer function of the optical filter as;
- (k) given τ
Specification