title: Fourier analysis for hydrostatic pressure sensing in a polarization-maintaining photonic crystal fiber.
abstract: We measured the hydrostatic pressure dependence of the birefringence and birefringent dispersion of a Sagnac interferometric sensor incorporating a length of highly birefringent photonic crystal fiber using Fourier analysis. Sensitivity of both the phase and chirp spectra to hydrostatic pressure is demonstrated. Using this analysis, phase-based measurements showed a good linearity with an effective sensitivity of 9.45 nm/MPa and an accuracy of ±7.8 kPa using wavelength-encoded data and an effective sensitivity of -55.7 cm(-1)/MPa and an accuracy of ±4.4 kPa using wavenumber-encoded data. Chirp-based measurements, though nonlinear in response, showed an improvement in accuracy at certain pressure ranges with an accuracy of ±5.5 kPa for the full range of measured pressures using wavelength-encoded data and dropping to within ±2.5 kPa in the range of 0.17 to 0.4 MPa using wavenumber-encoded data. Improvements of the accuracy demonstrated the usefulness of implementing chirp-based analysis for sensing purposes.
authors.affiliation: Department of Electronic Engineering, Tsinghua University, Beijing, China 100084. pchilds@physics.org
authors.forename: Paul
authors.initials: P
authors.lastname: Childs
authors.forename: Allan C L
authors.initials: AC
authors.lastname: Wong
authors.forename: H Y
authors.initials: HY
authors.lastname: Fu
authors.forename: Yanbiao
authors.initials: Y
authors.lastname: Liao
authors.forename: Hwayaw
authors.initials: H
authors.lastname: Tam
authors.forename: Chao
authors.initials: C
authors.lastname: Lu
authors.forename: P K A
authors.initials: PK
authors.lastname: Wai