Abstract: Methods and apparatus to control the acoustic properties of optical cables used as in-well oil and gas probes for acoustic monitoring, such as distributed acoustic sensing (DAS). One example aspect provides a solid path for the acoustic wave to propagate from an outside armor layer of the cable to the sensing optical waveguide embedded therein. Another example aspect offers ways to spatially dispose the optical sensing elements to create response delays indicative of the propagation speed and/or direction of an acoustic wave. Yet another example aspect provides ways to utilize additional spectral interrogation to increase ultimate spatial resolution. Yet another example aspect provides ways to locally vary the acoustic properties along the length of the cable.

Abstract: An illumination apparatus includes an optical apparatus configured to optically process laser light to produce illumination light such that speckle noise in the illumination light is reduced. The optical apparatus includes at least one collimator (130) configured to collimate the laser light and a diffuser (140) configured to diffuse the laser light.

Abstract: Distributed optical fibre sensor measures vibration, as a concurrent function of position along each of a plurality of sensing optical fibres, from properties of probe light backscattered within the sensing optical fibres. The sensor includes a light-pulse-generating probe light source, a detector, an optical switch. The sensor is arranged to control the optical switch such that all of the sensing optical fibres can be used concurrently to detect acoustic vibration, and an analyser is arranged to determine vibration, as a concurrent function of position along each of the sensing optical fibres, from the detected backscattered probe light.

Abstract: A scour monitoring system may provide a housing that is separated into multiple segments that are fluidically isolated from each other. The scour monitoring system may be position adjacent to a structure to be monitored for bridge scouring. Each of the segments may provide a water-swellable material positioned near or in contact with a fiber Bragg grating (FBG) cable. If water penetrates a segment, the water-swellable material may expand to deform the FBG cable. The wavelength of the FBG cable may be monitored periodically for changes, thereby providing moisture detection when a change in wavelength is detected.

Abstract: Provided is an apparatus for controlling a laser light propagation direction, including: a substrate configured to transmit at least a wavelength range of a laser light incident on the apparatus and deflected; and a metasurface disposed on the substrate, and comprising a plurality of nano-antennas, wherein each of the plurality of nano-antennas may include: a first contact and a second contact that are disposed apart from each other, and comprise an electrically conductive material to transmit at least the wavelength range of the laser light; and a semiconductor p-i-n heterostructure that disposed between the first contact and the second contact and comprises a p-region, an i-region and an n-region, which are disposed in parallel to the substrate.

Abstract: A molecularly imprinted polymer sensor for sensing a target molecule includes (a) a porous polymer film that is molecularly imprinted with a homolog of the target molecule and includes a conductive polymer having resistance sensitive to binding with the target molecule and a structural polymer providing porosity to the polymer film, and (b) interdigitated electrodes, located on a surface of the polymer film, for measuring a change in the resistance to sense said binding.

Abstract: A method and system for measuring a sample property (X) by means of photonic circuit (10). The photonic circuit (10) comprises at least two photonic sensors (11, 12) configured to modulate the light according to respective output signals (S1,S2) with periodically recurring signal values (V1, V2). The photonic sensors (11, 12) comprise a low range sensor (11) with a relatively low range or high sensitivity for measuring a change (?X) of the sample property (X) and a high range sensor (12) with a relatively high range or low sensitivity to measure the change (?X) of the sample property (X). The sample property (X) is calculated by combining the output signals (S1, S2) of the sensors (11, 12). Particularly, the second output signal (S2) of the high range sensor (12) is used to distinguish between recurring signal values (V1) in the first output signal (S1) of the low range sensor (11).

Abstract: Many monitoring systems, including distributed fiber optic sensing systems, are deployed to measure temperature, strain, acoustic, pressure, and electromagnetic data in a multi-well hydrocarbon field. By coupling disparate fiber optic cables together for strain sensing, a tubular cable is created that can be spooled and deployed as a single unit while allowing for multi-parameter sensing. Multiple tubular cables can measure and transmit sensing data from wellbores and geological formations. The data can be used to continually update a reservoir model and optimize production efficiency while also managing and mitigating subsidence by controlling injection and production rates.

Abstract: A microorganism detection system is provided for being disposed on a device to be detected which is closed, including a flow channel and a detection module. A fluid to be detected in the device to be detected flows in the flow channel. The detection module is disposed within the flow channel, including two slides, a microscopic module and at least one telescopic mechanism, each of the at least one telescopic mechanism is connected to one of the two slides and the flow channel. When the two slides approach each other, the fluid to be detected in a gap between the two slides is observable through the microscopic module.

Abstract: A distributed acoustic sensing method that includes sending a sequence of optical pulses along an optical fiber, of at least two different widths, demodulating backscattered light from the optical fiber to obtain interferometric phase measurements as a function of position, combining the interferometric phase measurements to obtain a set of fade-resistant phase measurements, and storing or displaying the set of fade-resistant phase measurements. A distributed acoustic sensing system that includes a transmitter that sends a sequence of optical pulses along an optical fiber, of at least two different widths, a receiver that demodulates backscattered light from the optical fiber to obtain interferometric phase measurements as a function of position and combines interferometric phase measurements to obtain a set of fade-resistant phase measurements, and a storage or display device.

Abstract: Arrays of integrated analytical devices and their methods for production are provided. The arrays are useful in the analysis of highly multiplexed optical reactions in large numbers at high densities, including biochemical reactions, such as nucleic acid sequencing reactions. The integrated devices allow the highly sensitive discrimination of optical signals using features such as spectra, amplitude, and time resolution, or combinations thereof. The arrays and methods of the invention make use of silicon chip fabrication and manufacturing techniques developed for the electronics industry and highly suited for miniaturization and high throughput.

Abstract: A method of monitoring thermomechanical behavior of an undersea pipe (2) transporting fluid under pressure and made by assembling unit pipe elements (4), comprising determining a mechanical signature specific to each unit pipe element, using a measurement cable (16) having an optical fiber sensor using Brillouin backscattering to measure deformation of the pipe element while it is subjected on land to various mechanical stresses in predetermined directions and magnitudes, and establishing a stiffness matrix associated with the mechanical signature of each pipe element, a step of determining a thermal signature specific to each unit pipe element, which step consists in measuring the temperature changes of the unit pipe element while it is being subjected on land to various different electrical heating powers, and in establishing a thermal transfer function associated with the thermal signature of each pipe element, and a monitoring step consisting of recovering.

Abstract: A method of monitoring mechanical behavior of an undersea pipe (2) transporting fluid under pressure and made by assembling a plurality of unit pipe elements (4). A calibration step is performed consisting of using a measurement cable having an optical fiber sensor to measure deformations experienced by each pipe element while it is subjected on land to various mechanical stresses in predetermined directions and magnitudes, and, on the basis of the measurements, establishing the mechanical signature of each pipe element. A monitoring step is performed consisting of using a measurement cable (18) having an optical fiber sensor that makes uses Brillouin backscattering and is helically positioned at constant pitch (p) on each pipe element with the handedness of the helical pitch alternating for two adjacent pipe elements to recover variations in optical signal injected into the sensors while the pipe is in service.

Abstract: Film-forming compositions are provided comprising: (a) a zwitterionic-functional polymer; and (b) an organometallic compound. Also provided are methods of reducing adhesion of an organic substance to a substrate and methods of treating a siliceous or metal (M) oxide-containing subterranean formation penetrated by a well using the film-forming compositions described above.

Abstract: A fiber optic sensor device comprising an optical fiber with a multilayer coating on the optical fiber at least in a fiber section of the optical fiber. The multilayer coating comprises a chrome layer on the optical fiber, a metal layer such as a copper layer on the chrome layer and an indium or lead layer on the metal layer. The indium or lead layer having a thickness larger than thicknesses of the chrome and metal layers, preferably with a thickness about equal to the radius of the optical fiber.

Abstract: An electrical cable includes a conductor assembly having a first conductor, a second conductor and an insulator surrounding the first conductor and the second conductor. The insulator has an outer surface. The conductor assembly extends along a longitudinal axis for a length of the electrical cable. The first conductor has a first core and a first conductive layer on the first core. The second conductor has a second core and a second conductive layer on the second core. The first and second cores are dielectric. The electrical cable includes a cable shield around the conductor assembly engaging the outer surface of the insulator and providing electrical shielding for the first and second conductors. The cable shield extends along the longitudinal axis.

Abstract: Devices, systems and techniques for measuring optical polarization-related parameters in optical materials and devices such as polarization maintaining (PM) fiber links based on polarization crosstalks that spatially distribute over a length of a material such as a PM fiber link.

Abstract: A sensing apparatus, system, and use method for selective detection of a target molecule in a gaseous medium with a limit of detection of less than 50 ppm are provided. The sensing apparatus comprises an optical fiber having a core with a tilted grating, and a coating assembly that is both active to surface plasmon resonance (SPR) and reversibly reactive to the target molecule to allow for repeated detection. Upon a compatible light propagating in the optical fiber, surface plasmon waves at an interface between the coating assembly and the medium can be generated to thereby derive information of the target molecule. Signals from core mode optical waves can additionally be used as inherent reference to remove influences of fluctuations from environmental factors and input power level. There is at least one range of concentrations for the target molecule allowing for linear measurement. Multiplexing of a plurality of sensing apparatuses is also disclosed.

Abstract: A pupil-replicating waveguide suitable for operation with a coherent light source is disclosed. A waveguide body has opposed surfaces for guiding a beam of image light. An out-coupling element is disposed in an optical path of the beam for out-coupling portions of the beam at a plurality of spaced apart locations along the optical path. Electrodes are coupled to at least a portion of the waveguide body for modulating an optical path length of the optical path of the beam to create time-varying phase delays between the portions of the beam out-coupled by the out-coupling element.

Abstract: Fronthaul monitoring systems and methods include a Radio Frequency (RF) analysis module configured to receive an optical RF signal for RF testing thereof; a fiber monitoring module configured to perform fiber monitoring testing; an optical switch configured to switch a port connected to the RF analysis module and the fiber monitoring module between one or more Remote Radio Heads (RRH); and a test coordinator software module configured to coordinate the RF testing and the fiber monitoring testing. The optical RF signal is at different wavelengths than a fiber test signal for the fiber monitoring testing, such that the RF testing and the fiber monitoring testing can be performed concurrently.

Abstract: Disclosed herein is an optical cable comprising a plurality of cable sensors helically wound around a support; and an outer jacket that is disposed on the plurality of cable sensors and surrounds the plurality of cable sensors; where each cable sensor comprises an optical fiber; where the optical fiber comprises an optical core upon which is disposed a cladding; a primary coating; a deformable material surrounding the optical fiber; and an outer tube surrounding the deformable material; where the optical fiber is of equal length to the outer tube; and where an allowable strain on the optical cable with zero stress on the optical fiber is determined by equations (1) and (2) below: ? = ? 2 ? ( D + d 2 ) 2 + p 2 p - ? 2 ? ( D - d 2 ) 2 + p 2 p = ? 2 ? dD p 2 = 10 ? ? dD p 2 ( 1 ) ? × 100 = Percent ? ? elongation ? ? or ? ? contraction ; ( 2 ) where d is the amount of optical fiber clearance for free movement

Abstract: To realize a reservoir computing system with a small size and reduced learning cost, provided is a laser apparatus including a laser; a feedback waveguide that is operable to feed light output from the laser back to the laser; an optical splitter that is provided in a path of the feedback waveguide and is operable to output a portion of light propagated in the feedback waveguide to outside; and a first ring resonator that is operable to be optically connected to the feedback waveguide, as well as a reservoir computing system including this laser apparatus.

Abstract: A chemical sensor, including a porous optical waveguide. The loss or index of refraction, or both, of the porous waveguide is affected by the presence of one or more chemicals of interest.

Abstract: The invention relates to a mounted module (20) for a motor vehicle (1), comprising an optical sensor system (3) that is suitable for a) monitoring a detection area (21) located outside the vehicle (1), b) triggering a signal for starting an authentication process between an ID generator (13) and the motor vehicle (1) if a user (10) is detected in the detection area (21), c) monitoring an actuation area (22) which is located outside the vehicle (1) and differs from the detection area (21), d) providing an operating signal for the vehicle (1) if a user is detected in the actuation area (22).

Abstract: Embodiments of the present disclosure include a low crosstalk, optical fiber based disturbance detection system that includes single-mode optical fiber (SMF) arranged into dual ring Sagnac interferometer wherein both rings share a common sensing section of optical fiber path length. Certain embodiments further include fiber Bragg gratings (FBG's), circulators and couplers to be able to separate the optical signals of the two rings of the dual ring Sagnac interferometer and to perform processing of their individual signals. Embodiments are also disclosed that enable the position of a physical disturbance, the magnitude of the physical disturbance and the frequency of the physical disturbance to be known.

Abstract: A system for tracking an instrument including an intraoperative transducer array configured to generate signals from array positions to generate real-time images of an area of interest. The instrument can be a penetrating instrument having a sensor mounted at a position of interest and being responsive to the signals from the array positions. A signal processing module can be provided and configured to determine a position and orientation of the instrument in accordance with the signals and to classify media of the position of interest based upon a response of the sensor to the signals from the array positions. An overlay module can be provided and configured to generate an overlay image registered to the real-time images to identify a position of the position of interest and provide feedback on the media in which the position of interest is positioned. A display can be provided and configured to provide visual feedback of the overlay image on the real-time images.

Abstract: A system comprises a first cannula comprising a proximal end and a cannula opening at the proximal end. The system further comprises a teleoperated surgical instrument, and a manually operated surgical instrument configured to be inserted into the cannula opening. The system further comprises a teleoperated manipulator, a controller, and a first position sensor coupled to the teleoperated surgical instrument, the first position sensor configured to provide a first sensor input to the controller. The system further comprises a second position sensor coupled to the manually operated surgical instrument, the second position sensor configured to provide a second sensor input to the controller, the second sensor input comprising an insertion depth of the manually operated surgical instrument into the first cannula.

Abstract: A distributed temperature sensing (DTS) system is connected to a buried fiber optic cable that is used to monitor a structure. The DTS system is operated to obtain temperature measurements along the length of the fiber cable. The temperature measurements are then used to calculate a measure of diurnal temperature variability at each point along the cable. This calculation is used to identify points at which the diurnal temperature variability changes rapidly over a short length of the cable. These points can be identified with features along the cable, such as splice chambers, where the cable burial conditions change. The known geographic location of these features can then be identified with specific distances along the fiber.

Abstract: A laser radar system using collocated laser beams to unambiguously detects a range of a target and a range rate at which the target is moving relative to the laser radar system. Another aspect of various embodiments of the invention may relate to a laser radar system that uses multiple laser radar sections to obtain multiple simultaneous measurements (or substantially so), whereby both range and range rate can be determined without various temporal effects introduced by systems employing single laser sections taking sequential measurements. In addition, other aspects of various embodiments of the invention may enable faster determination of the range and rate of the target, a more accurate determination of the range and rate of the target, and/or may provide other advantages.

Abstract: The invention is an electromechanical resonator, comprising a fixed portion and an oscillator oscillating at a resonant frequency and comprising a fluidic channel. The channel defines a fluidic circuit, can receive a fluid, and can be deformed at the resonant frequency. The resonator includes a waveguide, defining a photonic circuit, guiding a light wave between an input and an output of the waveguide and being able to be deformed at the resonant frequency. The waveguide input can be connected to a light source and the waveguide output can be connected to a photodetector able to form a signal representative of the light wave propagated by the waveguide towards the photodetector, the light wave being modulated at a frequency dependent on the resonant frequency. A variation in a mass of the fluid, inducing a variation in the resonant frequency, may be detected via the signal formed by the photodetector.

Abstract: A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

Abstract: A sensor system (10) and method for monitoring a powertrain (20) having a drive shaft (1). The sensor system (10) comprises an optical fibre (2) with a strain sensitive element (3). According to one aspect, a connection structure (4) is configured to hold at least a part of the optical fibre (2) with the strain sensitive element (3) at a radial distance (R2-R1) remote from the drive shaft (1) for amplifying the strain (S2) on the strain sensitive element (3) with respect to the strain (51) on the drive shaft (1). According to a further aspect, at least three respective lengths of one or more optical fibres follow parallel, e.g. helical, paths with respect to each other to distinguish different strain forces.

Abstract: An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.

Abstract: A photonic pressure sensor device includes a cantilever pivotally attached to a fixed mount. The cantilever has an electromagnetic reactive material located thereon that is configured to cause a movement of the cantilever based on a photonic pressure exerted on the electromagnetic reactive material from an electromagnetic radiation source incident on the material. An etalon is coupled to the cantilever such that a position of the etalon changes based on the movement of the cantilever. A light source is optically coupled to the etalon to provide a light beam to the etalon. The change in the position of the etalon causes interference of the light within the etalon resulting in an interference light beam. A light detector is positioned to receive the interference light beam from the etalon and configured to measure an intensity value for the interference light beam.

Abstract: In some embodiments, phonon based temperature measuring apparatuses include a light source positioned to direct a light toward a prism-resonant cavity interface of an optical resonant cavity inducing an evanescent wave that is guided into the resonant cavity having surface phonon polariton properties; a detector positioned proximate the resonant cavity and configured to detect reflected light from the prism-resonant cavity interface; and a temperature calculator coupled with the detector and configured to determine evanescent light coupling to one or more phonon polariton modes from the resonant cavity, calculate a quality factor as a function of a frequency spectrum of at least one of the one or more phonon polariton modes, and determine a temperature of a dielectric material within the resonant cavity as a function of the quality factor.

Abstract: A fiber optic sensor, a process for utilizing a fiber optic sensor, and a process for fabricating a fiber optic sensor are described, where a double-side-polished silicon pillar is attached to an optical fiber tip and forms a Fabry-Pérot cavity. In an implementation, a fiber optic sensor in accordance with an exemplary embodiment includes an optical fiber configured to be coupled to a light source and a spectrometer; and a single silicon layer or multiple silicon layers disposed on an end face of the optical fiber, where each of the silicon layer(s) defines a Fabry-Pérot interferometer, and where the sensor head reflects light from the light source to the spectrometer. In some implementations, the fiber optic sensor may include the light source coupled to the optical fiber, a spectrometer coupled to the optical fiber, and a controller coupled to the high-speed spectrometer.

Abstract: The present disclosure provides an apparatus and a method for measuring a concentration of pollutants in water. A passive Q-switched fiber laser outputs an evanescent wave to a to-be-tested water sample after emitting a Q-switched pulse laser signal and transmitting it via an evanescent field fiber, and based on an evanescent wave change caused by an absorption effect of the pollutants in the to-be-tested water sample to the evanescent wave and an output repetition frequency change of the passive Q-switched fiber laser due to the evanescent wave change, outputs an output repetition frequency result of the passive Q-switched fiber laser. The method is simple; and the apparatus based on the method is simple in structure and low in cost.

Abstract: In one embodiment, a device for measuring blood coagulation includes a substrate having a surface, an optical waveguide provided on the surface of the substrate, the waveguide having a tip, and means for spatially separating objects from the tip of the waveguide.

Abstract: The present invention is directed to an optical fiber grating having a core, that is capable of controlling the light signal transmission therethrough by causing at least one of: at least one spectral peak, and/or at least one spectral dip in its core light transmission spectrum, corresponding to at least one predetermined wavelength. The inventive optical fiber diffraction grating comprises at least one longitudinally positioned structural element of a predetermined geometric profile and that is configured for diffracting a portion of the transmitted light signal at at least one predefined wavelength thereof, from at least one core mode into at least one of: at least one cladding mode and/or at least one radiating mode. Various embodiments of a number of novel techniques for fabrication of the inventive optical fiber diffraction grating are provided, inclusive of a novel technique for fabricating the inventive grating from a single material.

Abstract: A device and system for detecting dynamic strain. The device comprises a longitudinally extending carrier and an optical fiber embedded along an outer surface of a length of the carrier. The optical fiber comprises at least one pair of fiber Bragg gratings (FBGs) tuned to reflect substantially identical wavelengths. The system comprises the device and an interrogator comprising a laser source and a photodetector. The interrogator is configured to perform interferometry by shining laser light along the optical fiber and detecting light reflected by the FBGs. The interrogator outputs dynamic strain measurements based on interferometry performed on the reflected light.

Abstract: A dome light assembly that includes a light-producing element comprising a polymeric film between two glass substrates, a reflective surface facing an interior, and a plurality of edges; and a controller configured to direct LED sources to (a) excite photoluminescent structures within the element to transmit decorative light patterns, and (b) transmit functional light patterns, into the interior. Further, the sources are configured to direct incident light into the edges.

Abstract: An optical sensor device includes an optical waveguide portion having a core, the core having a first refractive index, and a functional material layer coupled to the optical fiber portion, the functional material layer being made of a metal oxide material, the functional material layer being structured to have a second refractive index, the second refractive index being less than the first refractive index. The functional material layer may be a nanostructure material comprising the metal oxide material with a plurality of holes or voids formed therein such that the functional material layer is caused to have the second refractive index.

Abstract: A spectrometer-equipped lighting device detects substances in an environment around the device. A fiber detector is optically coupled to receive light from a light source. The fiber detector has a bare area from which emanates an evanescent wave of light surrounding an exterior of the fiber detector to interact with the environment in which the fiber detector is exposed. The spectrometer, optically coupled to an opposite end of the fiber detector, detects the light output and in response, generates signals representative of the spectral power distribution of the light of the evanescent wave that has interacted with the surrounding environment. A controller analyzes the spectrometer generated signals and initiates action based on the analysis of the generated signals or outputs a report indicating an environmental condition detected by the spectrometer-equipped device.

Abstract: Disclosed is a chip.

Abstract: A radio-opaque plastic scintillator detector (PSD) for use in various medical applications and methods of making and using the PSD. The method requires coating a plastic scintillator fiber with a radio-opaque material; cutting the scintillator fiber; stripping the end of a plastic fiber optic fiber; cutting the naked end of a plastic fiber optic fiber; inserting a closely fitting guide tube over the naked end and inserting the cut scintillating fiber into the guide tube; coating the detector end of the cable with a light opaque polymer or jacket and adding a connector to the other end.

Abstract: Disclosed is a planar waveguide including: a core (11) which is a flat plate through which light propagates; a cladding (12) which is a flat plate for reflecting the light in a state of being joined to an upper surface of the core (11); and a cladding (13) which is a flat plate for reflecting the light in a state of being joined to a lower surface of the core (11), in which each of the claddings (12) and (13) is a multilayer film in which multiple films made from different materials are layered. As a result, a material having a low index of refraction can be used as the material of the core (11), and the limit on materials usable as the material of the core (11) is relaxed.

Abstract: When a plurality of amplification devices each including a display unit are used in combination, deterioration in visibility of displayed information is prevented. An amplifier unit includes a connection mode specifying unit that detects another amplifier unit including another display unit which is disposed to form one display area along with the display unit and a display control unit that displays information in the display area formed by a plurality of display units.

Abstract: A planar lightwave circuit may include a set of components. The set of components may include an input waveguide to couple to an optical communications transceiver. The set of components may include an output waveguide to couple to the optical communications transceiver. The set of components may include a common port to couple to an optical fiber. The set of components may include a first polarization beam splitter. The set of components may include a second polarization beam splitter. The set of components may include a third polarization beam splitter. The set of components may include a rotator assembly including a Faraday rotator and a quarter-wave plate.

Abstract: A technique facilitates monitoring of flow conditions with respect to flow through a tubing. A distributed sensor is routed along an interior of the tubing to monitor flow conditions. For example, the distributed sensor may be routed over a length of the tubing having a lateral opening. Fluid is flowed along the distributed sensor and within the interior of the tubing. The distributed sensor is operated to measure strain which results from flow of the fluid along the distributed sensor. The strain may then be evaluated to determine a change in a flow condition, such as a change in a flow condition related to the lateral opening.

Abstract: Systems and methods that use a differential spectral liquid level sensor to measure the level of liquid in a reservoir (e.g., a fuel tank or other storage container). The use of a differential spectral liquid level sensor solves the problem of common-mode intensity variations (i.e., intensity variations not due to the level of the liquid) by having two different wavelengths propagate through the same optical path but have different spectral attenuations in the liquid. By determining the ratio of the received optical powers, common-mode intensity variations can be neutralized, thereby enhancing the accuracy of the received power reading and the resulting liquid level indication.