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 transmission spectrum as a function of wavelength comprising a plurality of local transmission maxima, the local transmission maxima each having a maximum power at a transmission peak wavelength, the fiber Bragg grating having a group index spectrum as a function of wavelength;
• generating light from a narrowband optical source, the narrowband optical source in optical communication with a first optical path and a second optical path, wherein the light is split into a first portion and a second portion;
• and
• transmitting the first portion of light along the first optical path extending along and through the length of the fiber Bragg grating at a group velocity,
• wherein the light has a wavelength at or in the vicinity of a wavelength at which one or more of the following quantities is at a maximum value:
• (a) the product of the group index spectrum and a square root of the power transmission spectrum, (b) the slope of a product of the group index spectrum and one minus the power transmission spectrum, and (c) the slope of a product of the group index spectrum and the power transmission spectrum.