MULTI-PEAK REFERENCE GRATING

Methods and apparatus are provided for using a multi-peak reference grating as an optical reference element to produce an optical spectrum with a plurality of reference wavelength peaks spanning a desired wavelength range. This multi-peak reference grating is suitable for use in swept-wavelength interrogation systems, such as those utilizing Bragg grating sensors. Each of the reference wavelength peaks may be characterized for absolute wavelength over a range of environmental operating conditions, such that the absolute wavelength of each reference wavelength peak can be found at any time given the contemporaneous environmental operating condition. This reference grating is interrogated concurrently with the Bragg grating sensors, and the position of each sensor peak relative to the reference grating peaks is used to calculate the absolute wavelength of each sensor (and hence, the corresponding parameter of interest).