An apparatus for determining a property, the apparatus including: an optical fiber having a series of fiber Bragg gratings, each fiber Bragg grating in the series being characterized by a light reflection frequency at which the fiber Bragg grating reflects light; wherein: the light reflection frequency for each fiber Bragg grating is different from the light reflection frequency of each adjacent fiber Bragg grating to minimize resonance of light between at least two of the fiber Bragg gratings in the series; at least two fiber Bragg gratings in the series have light reflection frequencies that overlap; and a change in the light reflection frequency of each fiber Bragg grating in the series is related to the property at the location of the each fiber Bragg grating.