System and method for measuring perturbations using a slow-light fiber Bragg grating sensor

A method of using a fiber Bragg grating comprising:

• providing a fiber Bragg grating comprising a substantially periodic refractive index modulation along a length of the fiber Bragg grating, wherein the fiber Bragg grating has a power reflection spectrum as a function of wavelength, a power transmission spectrum as a function of wavelength, and a group delay spectrum as a function of wavelength, wherein the power transmission spectrum as a function of wavelength comprises one or more resonance peaks, each comprising a local maximum and two non-zero-slope regions with the local maximum therebetween;
• generating light from a narrowband optical source, the narrowband optical source in optical communication with the fiber Bragg grating such that a transmitted portion of the light is transmitted along the length of the fiber Bragg grating and a reflected portion of the light is reflected from the fiber Bragg grating;
• and
• detecting an optical power of the transmitted portion of the light, the reflected portion of the light, or both the transmitted portion of the light and the reflected portion of the light with at least one optical detector,
• wherein the light has a wavelength at a non-zero-slope region of a resonance peak of the one or more resonance peaks, wherein the resonance peak is selected such that one or more of the following quantities, evaluated at the local maximum of the resonance peak, is at a maximum value:
• (a) the product of the group delay spectrum and the power transmission spectrum, and (b) the product of the group delay spectrum and one minus the power reflection spectrum.

A method of configuring an optical device to be used as an optical sensor, the optical device comprising a fiber Bragg grating and a narrowband optical source in optical communication with the fiber Bragg grating, the narrowband optical source configured to transmit light to the fiber Bragg grating such that a transmitted portion of the light is transmitted along the length of the fiber Bragg grating and a reflected portion of the light is reflected from the fiber Bragg grating, the fiber Bragg grating comprising a substantially periodic refractive index modulation along a length of the fiber Bragg grating, the method comprising:

• determining at least one of a power reflection spectrum of the light as a function of wavelength for the fiber Bragg grating and a power transmission spectrum of the light as a function of wavelength for the fiber Bragg grating, wherein the power transmission spectrum as a function of wavelength comprises one or more resonance peaks, each comprising a local maximum and two non-zero-slope regions with the local maximum therebetween;
• determining a group delay spectrum of the light as a function of wavelength for the fiber Bragg grating;
• selecting a resonance peak of the one or more resonance peaks, the resonance peak selected such that one or more of the following quantities, evaluated at the local maximum of the selected resonance peak, is at a maximum value:
• (a) a product of the group delay spectrum and the power transmission spectrum and (b) a product of the group delay spectrum and one minus the power reflection spectrum;
• and
• configuring the fiber Bragg grating and the narrowband optical source such that the light from the narrowband light source has a wavelength at a non-zero-slope region of the two non-zero-slope regions of the selected resonance peak.