Temperature-insensitive strain measurement using in-fiber Bragg gratings inscribed in photonic crystal fiber

Two gratings with closely spaced center-wavelengths are written in either side of a splice between two cascaded photonic crystal fibers of same diameter. The relative wavelength-shifts in response to the temperature can be compensated by means of filling rational fluid material into the cladding air-holes. Separate measurement of strain with a high sensitivity can be achieved just by analyzing the wavelength-shifts of the reflection peaks. The presented discrimination method can well restrain the cross-sensitivity effect, and render a new category of inherently temperature-insensitive strain sensors.