Optical Fiber Sensors: introduction to the feature issue.

This special issue contains a collection of papers on optical fiber sensors that were originally presented and published in a more succinct form in conjunction with the 27th International Conference on Optical Fiber Sensors (OFS) held in Alexandria, Virginia, United States, from 29th August to 2nd September, 2022.

Optical frequency dependence of the light shift effect for vector magnetometry with cesium.

Atomic vapor magnetometers have demonstrated very high sensitivity to the magnitude of the magnetic field. Vector field measurements are possible using bias fields applied to the vapor. For remote operation, the bias field can be generated using the optical light shift (LS) effect created with an optical beam delivered through optical fiber.

Optical phase response to temperature in a hollow-core photonic crystal fiber.

Analysis of previous measurements of thermal phase sensitivity in hollow core photonic crystal fibers is presented with additional new corroborating measurements, resolving a discrepancy in previously reported results. We extend an existing derivation of thermo-mechanical phase sensitivity in solid- and hollow-core photonic crystal fiber to also include kagome lattice photonic crystal fibers. Measured thermal phase response is shown to agree with theoretical prediction to within a few percent.

Noise induced in optical fibers by double Rayleigh scattering of a laser with a 1/fν frequency noise.

We study, theoretically and experimentally, intensity noise induced by double Rayleigh scattering in long optical fibers. The results of the theoretical model are compared to experimental results performed with a high-coherence-length laser with a frequency noise spectrum that is dominated by 1/fν noise. Excellent quantitative agreement between theoretical and experimental RF spectra were obtained for frequencies as low as 10 Hz and for fiber lengths between 4 and 45 km.

Characterization of laser-driven shock waves in solids using a fiber optic pressure probe.

Measurement of laser-driven shock wave pressure in solid blocks of polymethyl methacrylate is demonstrated using fiber optic pressure probes. Three probes based on a fiber Fabry-Perot, fiber Bragg grating, and interferometric fiber tip sensor are tested and compared. Shock waves are generated using a high-power laser focused onto a thin foil target placed in close proximity to the test blocks.

Comment on "Probing the ultimate limit of fiber-optic strain sensing".

Gagliardi et al. (Reports, 19 November 2010, p. 1081) described an ultrahigh-resolution fiber-optic strain sensor.

Characterization of strong fiber Bragg gratings using an applied thermal chirp and iterative algorithm.

Coupling coefficients of various grating types and strengths are calculated from measurements of the complex reflectivity using an applied thermal chirp and optical frequency domain reflectometry (OFDR). The complex reflectivity is then utilized by a layer peeling algorithm to determine the coupling coefficient of the thermally chirped grating. A guess of the temperature profile enables the coupling coefficient of the unchirped grating to be estimated.

Improved implementation of optical space domain reflectometry for characterizing the complex coupling coefficient of strong fiber Bragg gratings.

Optical space domain reflectometry (OSDR) implemented with a novel interferometric characterization method is demonstrated to be an accurate technique for characterizing the complex coupling coefficient of strong fiber Bragg gratings. A theoretical model is also presented, incorporating the effect of the heat perturbation shape, which accurately predicts the measurement behavior. It is shown that the measurement accuracy and spatial resolution are dramatically improved by removing the effect of the heat perturbation shape on the reconstructed profile using a deconvolution technique.

Rapid characterization of the ultraviolet induced fiber Bragg grating complex coupling coefficient as a function of irradiance and exposure time.

We report the application of optical frequency domain reflectometry and a discrete-layer-peeling inverse scattering algorithm to the spatial characterization of the UV induced complex coupling coefficient during fiber Bragg grating growth. The fiber grating is rapidly characterized using this technique to give irradiance dependent growth as a function of exposure time, thereby providing the complete characterization of the coupling coefficient in the form of a "growth surface," which is related to the fiber's photosensitivity. We compare measurements of fiber Bragg grating growth in SMF-28 when exposed to continuous wave 244 nm irradiation from 0 to 90 W cm(-2) for exposure times up to 3230 s with a selection of other fibers including high germanium concentration fiber and erbium doped fiber.