Method and apparatus for estimating chromatic dispersion in fibre bragg gratings
AssigneeDefence Science and Technology Organisation
InventorsMark Englund, Eric Carl Magi
Life of this patent
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Abstract
The present invention provides a method and apparatus for obtaining a measure of the chromatic dispersion of a fibre bragg grating, the method comprising: disposing the grating in a reflection arm of an interferometer; inputting probe laser light into the interferometer; stepping the wavelength of the light across the reflection bandwidth of the grating, while at each step modulating the wavelength by a wavelength modulation less than the size of the respective step, and thereby producing a resulting phase modulation; and demodulating the phase modulation and determining therefrom a measure of the chromatic dispersion.
Claims14
A method of obtaining a measure of the chromatic dispersion of a fibre bragg grating, comprising:
- disposing said grating in a reflection arm of an interferometer;
- inputting probe laser light into said interferometer;
- stepping the wavelength of said light across the reflection bandwidth of said grating, while at each step modulating said wavelength by a wavelength modulation less than the size of said respective step, and thereby producing a resulting phase modulation;
- and
- demodulating said phase modulation and determining therefrom a measure of said chromatic dispersion.
A method as claimed in any one of the preceding claims, wherein said wavelength modulation is much less than said size of said respective step.
A method as claimed in any one of the preceding claims, including normalising the response of said interferometer by means of a Mach Zehnder interferometer.
A method as claimed in any one of the preceding claims, wherein said demodulating is by means of a passive homodyne demodulation technique.
An apparatus for obtaining a measure of the chromatic dispersion of a fibre bragg grating, having:
- an interference means optically connectable to said fibre bragg grating to form an interferometer;
- tunable laser source means for providing wavelength tunable laser light so that the wavelength of said tunable laser source can be stepped across the reflection bandwidth of said grating;
- modulation means for modulating said wavelength of said light by an amount less than said steps;
- a photo-detector for detecting light from said interferometer and producing a signal indicative thereof;
- demodulation means for demodulating said signal;
- and
- computation means for determining a measure of said chromatic dispersion from said demodulated signal.
Dependencies are inferred from the claim text.