Systems and methods for improved interferometric imaging are presented. One embodiment is a partial field frequency-domain interferometric imaging system in which a light beam is scanned in two directions across a sample and the light scattered from the object is collected using a spatially resolved detector. The light beam could illuminate a spot, a line or a two-dimensional area on the sample. Additional embodiments with applicability to partial field as well as other types of interferometric systems are also presented.

The present invention provides a reusable probe for use with a device for measuring the absolute value of the refractive index of a liquid by immersion uses the optical properties of a cylindrical waveguide with a solid core and normal angle of incidence of the light source.

The present invention provides a method and device for on-line detection of the salinity of seawater. A sweep frequency synchronous signal controls a sweep frequency laser light source such that the wavelength of a frequency modulation light wave output by the sweep frequency laser light source is a periodic saw-tooth wave signal. The frequency modulation light wave is divided into two beams, respectively transmitted to a refractive index probe and a temperature probe in seawater. The refractive index probe is an interference instrument structure, and the frequency value of an interference light intensity signal fed back by the refractive index probe is related to the refractive index of seawater. The refractive index of seawater is calculated by performing discrete Fourier transformation on the interference light intensity signal. The temperature probe is internally provided with a fiber Bragg grating, and the Bragg wavelength of the reflection spectrum of the temperature probe is related to the temperature of the seawater. The sweep frequency synchronous signal and the reflection light intensity signal of the fiber Bragg grating are subjected to synchronous discrete sampling, and the temperature value of the seawater is calculated according to a grating temperature sensor demodulation algorithm. The salinity value of the detected seawater is obtained by solving an empirical equation according to the obtained refractive index, the temperature value and the average wavelength of the frequency modulation light wave, thereby implementing on-line detection of the salinity of seawater.

A photonic integrated circuit for an interferometric sensor includes a first waveguide called sensitive arm wherein a first portion of the light radiation is propagated, the sensitive arm being exposed to a first ambient medium and to at least one compound to be detected inducing a modification of the local refractive index perceived by the evanescent part of the electromagnetic field of the first portion of the light radiation, and a second waveguide called reference arm wherein a second portion of the light radiation is propagated, an encapsulation layer encapsulating the reference arm, the encapsulation layer being impermeable to the compound or compounds to be detected, so that the reference arm is exposed only to a second ambient medium, substantially of the same nature as the first ambient medium and without the compound to be detected and interferometric sensor comprising a photonic integrated circuit according to the invention.

A method of identifying the material and determining the physical thickness of each layer in a multilayer structure is disclosed. The method includes measuring the optical thickness of each of the layers of the multilayer object as a function of wavelength of a light source and calculating a normalized group index of refraction dispersion curve for each layer in the multilayer structure. The measured normalized group index of refraction dispersion curves for each of the layers is then compared to a reference database of known materials and the material of each layer is identified. The physical thickness of each layer is then determined from the group index of refraction dispersion curve for the material in each layer and the measured optical thickness data. A method for determining the group index of refraction dispersion curve of a known material, and an apparatus for performing the methods are also disclosed.

The present disclosure provide a gas monitoring device, a gas monitoring system, a gas monitoring method, a cabinet, and a computer readable storage medium. The gas monitoring device includes: a tubular housing, a light transmission module arranged at one end of the tubular housing, and a gas detecting module arranged at the other end of the tubular housing, in which a first end surface of the light transmission module, a second end surface of the gas detecting module and the tubular housing form a cavity, and the first end surface and the second end surface are parallel to each other; the light transmission module is configured to input incident light to the cavity, and the gas detecting module is configured to adjust a distance between the second end surface and the first end surface according to a concentration of the gas to be detected.

A micro-resonator and fiber taper based sensing system, which uses mode splitting or frequency shift methods and polarization measurements for particle sensing.

A sensing system for monitoring a composition of a downhole fluid in a well, where the sensing system includes: a light source, an optical waveguide, an evanescent field sensing element that is indirect contact with a downhole fluid, and a detector. The light source is operable for emitting a beam and includes a frequency comb generator configured to modify at least a portion of the beam into a sensing comb beam. The evanescent field sensing element provides attenuated internal reflection of the sensing comb beam at the interface between the evanescent field sensing element and the downhole fluid, and the portion of the sensing comb beam interacts with the fluid to form at least a portion of an interacted beam. The detector obtains a spectral distribution of the interacted beam.

A sensor for use in detecting an analyte, the sensor comprising a monofibre waveguide and a reactive film comprising a nanoporous material disposed at a distal end of the monofibre waveguide. The sensor is rugged, highly sensitive, and allows for rapid detection of analytes in very low amounts.

An in-situ, non-destructive sensor device, system and method are provided to detect or assess fouling at a very early stage of development. They can be used to detect or assess fouling on a surface of an aquatic system. They can be used to obtain a depth profile of the fouling. Data concerning the depth profile can be extracted and used to assess the fouling on the surface. In one or more aspects, the method can include providing an optical tomography spectrometer; optically positioning the optical tomography spectrometer in association with a surface of an area to be assessed for fouling in an aqueous system; irradiating the surface; acquiring, from irradiating the surface, a plurality of signals as a function of a distance from the surface at different times; extracting data from the signals as a function of the distance to obtain a depth profile of the surface at the different times; and determining a change in the depth profile between the different times to assess fouling on the surface.