Method and apparatus for measuring chromatic dispersion in optical fibers
AssigneeJDS Uniphase Corporation
InventorsMartin Achtenhagen, Idan Mandelbaum, Maxim Bolshtyansky
Life of this patent
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Abstract
An apparatus for measuring chromatic dispersion in a waveguide uses a probe signal and a modulated pump signal which are coupled together into a waveguide. The modulated pump signal causes spatial and temporal Raman gain modulation of the probe signal. The amplitude of the pump signal is modulated and the frequency response of the probe signal at the output end of the waveguide is measured. The chromatic dispersion of the waveguide at a given wavelength is determined from the measurements. The probe signal is provided by a CW laser or corresponds to the ASE generated by the pump signal.
Claims20
A method of measuring group delay in an optical waveguide, the method comprising the steps of:
- a) providing a modulated pump signal to the optical waveguide;
- b) allowing the pump signal to propagate within the optical waveguide so as to generate gain within the waveguide, the gain having the modulation of the pump signal impressed thereon;
- c) varying the modulation frequency of the pump signal;
- d) measuring a frequency response of the modulated gain while the modulation frequency of the pump signal is varied;
- and
- e) determining the group delay from the frequency response of the modulated gain.
A method for measuring chromatic dispersion of an optical waveguide having an input end and an output end, the method comprising the steps of:
- a) inputting a modulated pump signal into the input end of the waveguide to generate Raman gain in the waveguide,
- b) inputting a probe signal into the input end of the waveguide, the probe signal having a wavelength that is within Raman gain band characteristic of the waveguide,
- c) combining the pump signal and the probe signal at the input end of the waveguide,
- d) impressing the modulation of the pump signal on the probe signal through temporal and spatial Raman gain modulation in the waveguide,
- e) varying the modulation frequency of the pump signal,
- f) measuring frequency response of the probe signal at the output end of the waveguide while the modulation frequency of the pump signal is varied,
- g) determining the group delay from the frequency response of the probe signal,
- h) varying the wavelength of the probe signal,
- i) repeating steps a) to g) for different probe wavelengths to determine a relationship of group delay and wavelength, and
- j) determining the chromatic dispersion of the waveguide from said relationship.
An apparatus for measuring chromatic dispersion of a waveguide having an input end and an output end, the apparatus comprising:
- a Raman pump source operatively coupled to the input end of the waveguide, the Raman pump source for providing a pump signal to the input end;
- a modulator coupled to the Raman pump source, the modulator for modulating the Raman pump signal;
- and,
- a detector operatively coupled to the output end of the waveguide, the detector for measuring, at the output end of the waveguide, a frequency response of a probe signal simultaneously propagating through the waveguide with the modulated Raman pump signal.
Dependencies are inferred from the claim text.