Method and apparatus for measuring chromatic dispersion in optical fibers
AssigneeJDS Uniphase Corporation
InventorsMartin Achtenhagen, Idan Mandelbaum
Life of this patent
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Abstract
An apparatus for measuring chromatic dispersion in a waveguide uses a CW laser 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.
Claims12
A method for measuring group delay of an optical waveguide having an input end and an output end, the method comprising:
- a) inputting a modulated narrowband pump signal into the input end of the waveguide to generate Raman gain in the waveguide,
- b) inputting a narrowband 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, and
- g) determining the group delay from the frequency response of the probe signal.
A method for measuring chromatic dispersion of an optical waveguide having an input end and an output end, the method comprising:
- a) inputting a modulated narrowband pump signal into the input end of the waveguide to generate Raman gain in the waveguide,
- b) inputting a narrowband 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 source of a probe signal operatively coupled to the input end of the waveguide,
- a source of a Raman wavelength pump signal operatively coupled to the input end of the waveguide,
- a modulator means coupled to the source of a pump signal to modulate the pump signal to be input into the waveguide,
- means for separating the probe signal from the pump signal at the output end of the waveguide, and
- detector means for detecting and measuring, at the output end of the waveguide, frequency response of the probe signal to the frequency modulation.
Dependencies are inferred from the claim text.