Measuring chromatic dispersion in an optical wavelength channel of an optical fiber link
OwnerFred L. Heismann, Brandon C. Collingsinventors
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Abstract
Two intensity modulated test signals are generated with precise frequency offset from a single laser source, and multiplexed into a combined test signal. The two modulated signals are demultiplexed at a receiver using a fixed periodic optical filter with complementary output ports. Group velocity dispersion/chromatic dispersion is measured over a large dynamic range, using pseudo-random intensity modulation and digital demodulation techniques.
Claims29
A method for measuring chromatic dispersion of a selected wavelength channel in an optical fiber link, which transmits a plurality of wavelength division multiplexed (WDM) channels, comprising:
- a) producing an optical signal at a selected wavelength within the selected wavelength channel;
- b) modulating the optical signal with a first high frequency modulation signal having a predetermined frequency and amplitude to generate first and second sideband test signals comprising modulated light symmetrically disposed about the selected wavelength within the selected wavelength channel;
- c) modulating the first and second sideband test signals with a second lower frequency modulation signal for impressing a low frequency amplitude modulation on the first and second sideband test signals;
- d) coupling the first and second sideband test signals into a first point in the optical fiber link;
- and
- e) measuring a differential time delay between the modulated light in the first and second sideband test signals at a second point in the optical fiber link in order to determine the chromatic dispersion in the selected wavelength channel of the optical fiber link.
A system for measuring chromatic dispersion of a wavelength channel in an optical fiber link, which transmits a plurality of WDM channels, comprising:
- a laser source for producing an optical signal at a selected wavelength in the wavelength channel;
- a first electro-optic modulator for modulating the optical signal with a first high frequency modulation signal having a frequency and amplitude to generate first and second sideband test signals symmetrically disposed about the selected wavelength within the wavelength channel;
- a second electro-optic modulator for modulating the first and second sideband test signals with a second low frequency modulation signal for impressing a low frequency amplitude modulation on said first and second sideband test signals;
- a combiner for combining the first and second sideband test signals forming a combined test signal;
- a coupler for coupling the combined test signal into a first point in the optical fiber link;
- and
- a receiver at a second point of the optical fiber link for receiving the combined test signal, and measuring a phase difference between the two sideband test signals to determine the chromatic dispersion of the optical fiber link.
Dependencies are inferred from the claim text.