Polarimetric Sensor Research Articles

Passive three-dimensional imaging using polarimetric diversity

The results of experiments in developing a method for extracting three-dimensional information from a scene by means of a polarimetric passive imaging sensor are summarized. This sensor provides a full Stokes vector at each sensor pixel location from which degree and angle of linear polarization are computed. The angle of linear polarization provides the azimuth angle of the surface normal vector. The depression angle of this surface normal vector is obtained in terms of the emitting object's index of refraction from the solution of an equation derived from Fresnel equations, Snell's law, and percent of linear polarization. Results of the application of this approach to simulated infrared polarimetric data are provided.

Acoustic emission monitoring using a polarimetric Single Mode optical fibre sensor

Since the hydrocarbon reservoirs in Europe are rapidly depleting, there is a need for new 'intelligent' technology for the efficient commercial exploitation of the remaining hydrocarbon reservoirs: an intelligent and high-temperature, corrosion and fatigue resistant thermoplastic composite coiled tubing. This paper describes the polarimetric Fibre Optic Sensor and accompanying advanced transient signal detection techniques for an early detection of damage in this new type of intelligent composite tubing built for drilling and exploiting hydrocarbon reservoirs. The capabilities of the new optical system for detecting growing damage are demonstrated by carrying out bending tests on short test models of the tube.

All-fiber quasi-distributed polarimetric temperature sensor

This paper presents an all-fiber design of a quasi-distributed polarimetric temperature sensor array that utilizes commercially available single polarization and high birefringence fibers. The modulation depth of temperature induced loss and the operational temperature range of individual sensors in the network are set by the rotational alignment of fibers before fusion splicing and through fine adjustment of the sensing fiber lengths. A practical sensor network was built with sensors that operated in the temperature range from 0 to 100 C. Individual sensors in the network generated temperature dependent loss that changed proportionally from 0.9 to 1.8 dB. With current standard telecommunication OTDRs, more than 20 prototype sensors could be interrogated.

Thermooptical sensitivity analysis of highly birefringent polarimetric sensing photonic crystal fibers with elliptically elongated veins

The spectral and thermooptical sensitivity responses of highly birefringent photonic crystal fibers (PCFs) with elliptically elongated veins integrated in their profile are being investigated using a novel sensitivity analysis based on an accurate semivectorial modal solver combined with temperature-dependent Sellmeier equations for pure silica and dry air. We demonstrate that by an appropriate selection of the design parameters it is possible to optimize the sensitivity of the modal birefringence or even to obtain null response at specific wavelengths. Thus, our investigation adds evidence to the potential use of highly birefringent PCFs as polarimetric sensors. Optimized overall temperature sensitivity could be obtained up to 7.5middot10-7 K-1 at operational wavelength of 1.55 mu m

Review of passive imaging polarimetry for remote sensing applications

Imaging polarimetry has emerged over the past three decades as a powerful tool to enhance the information available in a variety of remote sensing applications. We discuss the foundations of passive imaging polarimetry, the phenomenological reasons for designing a polarimetric sensor, and the primary architectures that have been exploited for developing imaging polarimeters. Considerations on imaging polarimeters such as calibration, optimization, and error performance are also discussed. We review many important sources and examples from the scientific literature.

Interaction between optical fibre sensors and matrix cracks in cross-ply GFRP laminates. Part 2: Crack detection

Polarimetric optical fibre sensors have been embedded within the 0° ply and close to the 0°/90° interface of transparent cross-ply GFRP coupons. The coupons have been subjected to an increasing quasi-static load so that transverse ply cracks initiate and propagate across the coupon. Crack accumulation has been monitored using the optical output signal from the polarimetric sensor, strain measurements from a long gauge-length extensometer, load recordings during the test and by video recording of crack development. These combined observations have enabled a direct correlation to be made between matrix crack growth past the sensor and a step-change in the sensor response. The use of band-pass FFT filtering has demonstrated that such cracks could be detected in real time.

Performance analysis of all-fiber polarimetric strain sensor for composites structural health monitoring

An improved design comprising a multifiber configuration for a polarimetric fiber optic sensor in real time structural health monitoring is presented in this paper. The sensor is in the form of a multifiber assembly composed of a high-birefringent (HiBi) sensing fiber and a single mode polarization maintaining (PM) fiber or a HiBi fiber as a lead-in and lead-out fiber, all spliced in sequence. The polarization behavior of the assembly is analyzed theoretically using Stokes matrix method for the monochromatic case. Based on this model a phase shift compensation method for multifiber sensors is proposed. The design also helps reduce the bulky optical component in the sensor. The static and dynamic responses of these multifiber sensors are experimentally evaluated to test the structural integrity of composites.

Fiber lasers with hybrid birefringence resonators

We propose the combination of low- and high-birefringence fibers (Low-Bi and Hi-Bi, respectively) to form a hybrid birefringence resonator. The transmission characteristics as a function of different parameters for the fibers used within these hybrid resonators are obtained by means of Jones matrix analysis. This yields information on fiber laser features such as polarization mode-beating frequencies (PMB), which are used as readout for polarimetric sensors. We compare theoretical predictions with experimental results on the dependence of PMB frequencies as a function of wavelength and effective birefringence of the laser cavity. Applications of this hybrid fiber laser arrangement for polarimetric sensors and wavelength monitoring through PMB frequencies are also discussed. The results provide a simple way for optimizing fiber laser parameters and increase the sensitivity of PMB signals to wavelength variations.

Remote sensing using passive infrared Stokes parameters

We address the problem of detecting vehicle targets on the ground by means of an autonomous polarimetric sensor on board a high-altitude air- or spaceborne platform. We studied a sensor system that incorporates a micropolarizer array, a microscanner, and digital signal processors that host algorithms for detecting small targets. These algorithms use statistical techniques to fuse a target's Stokes-vector infrared signature measurements. Fusion is achieved by constructing the joint statistical measures for the target's polarization states. Those states are expressed in terms of the intensity, the percentage of linear polarization, and the angle of the polarization plane. The performance of the sensor system on synthetic polarimetric infrared imagery was evaluated. Relatively good detection and low false-alarm probabilities were achieved even when the number of pixels on targets is as small as four. This is the first report of the development and evaluation of automatic detection in polarimetric imagery containing targets subtending only a small number of pixels.

The Use of Fibre Optic Sensors for Damage Detection and Location in Structural Materials

The measurement of changes in the properties of ultrasonic Lamb waves propagating through structural material has frequently been proposed as a method for the detection of damage. In this paper we describe work that uses optical fibre sensors to detect the Lamb waves and show that the directional properties of these sensors allow us to not only detect damage, but also to locate it. We look at two types of optical fibre sensor, a polarimetric sensor and the fibre Bragg grating. The polarimetric sensor measures the change in birefringence of a fibre caused by the pressure wave of the ultrasound acting upon it. This is an integrated sensor since the fibre length bonded to the sample needs to be greater than the ultrasonic wavelength in order to obtain the required sensitivity. The maximum sensitivity of this sensor is when the fibre is positioned normal to the direction of wave propagation. Fibre Bragg gratings are essentially point sensors since the grating length needs to be a fraction of the ultrasound wavelength to obtain maximum sensitivity. Ultrasound is detected mainly through the in-plane strain it produces and maximum sensitivity is therefore produced when the grating is aligned parallel to the direction of wave propagation. Holes drilled into sample plates can be detected using both type of sensor by examining the changes in either the transmitted Lamb wave or through detection of the reflections produced by the hole. The sensitivity of the technique is shown to be determined by the relative positions of the acoustic source, the hole and the sensor. If we use fibre Bragg gratings in a rosette configuration (i.e. 3 gratings forming an equilateral triangle) then the direction of the Lamb wave can be determined using the directional sensitivities of the gratings. Using two such rosettes allows us to calculate the source of the wave from the intersection of two of these directions. If the source of the wave is the hole (which acts as a passive source), then the location of that hole can be determined.

The polarimetric 𝒢 distribution for SAR data analysis

AbstractRemote sensing data, and radar data in particular, have become an essential tool for environmental studies. Many airborne polarimetric sensors are currently operational, and many more will be available in the near future including spaceborne platforms. The signal‐to‐noise ratio of this kind of imagery is lower than that of optical information, thus requiring a careful statistical modelling. This modelling may lead to useful or useless techniques for image processing and analysis, according to the agreement between the data and their assumed properties. Several distributions have been used to describe synthetic aperture radar (SAR) data. Many of these univariate laws arise by assuming the multiplicative model, such as Rayleigh, square root of gamma, exponential, gamma, and the class of 𝒦I distributions. The adequacy of these distributions depends on the detection (amplitude, intensity, complex, etc.), the number of looks, and the homogeneity of the data. In Frery et al. (1997), another class of univariate distributions, called 𝒢, was proposed to model extremely heterogeneous clutter, such as urban areas, as well as other types of clutter. This article extends the univariate 𝒢 family to the multivariate multi‐look polarimetric situation: the 𝒢p law. The new family has the classical polarimetric multi‐look 𝒦p distribution as a particular case, but another special case is shown to be more flexible and tractable, while having the same number of parameters and fully retaining their interpretability: the 𝒢 law. The main properties of this new multivariate distribution are shown. Some results of modelling polarimetric data using the 𝒢 distribution are presented for two airborne polarimetric systems and a variety of targets, showing its expressiveness beyond classical models. Copyright © 2004 John Wiley & Sons, Ltd.

A novel all-fibre configuration for a flexible polarimetric current sensor

In this paper a polarimetric fibre-optics current sensor in a new highly versatile all-fibre configuration is described. The optical configuration is particularly simple and is based on a back-and-forth propagation through a twisted sensing fibre. This results in a very flexible sensing cable which can be adapted to a great number of existing power installations, by simply winding the fibre around the uninterrupted electrical conductor. The prototype presented here is designed to measure ac and dc currents with an excellent accuracy over more than three decades.

비틀린 광섬유 센서코일을 이용한 편광분석형 광섬유 전류센서

보호계전 시스템의 전류센서로 사용할 목적으로 편광분석형 광섬유 전류센서를 개발하였다. 광섬유의 선형복굴절에 의한 출력의 왜곡을 최소화하기 위하여 단일모드 광섬유를 미터 당 20회 이상 비틀고 그 끝단에 FRM(Faraday rotator mirror)을 부착하여 센서코일을 제작하였다. 광섬유 센서코일의 비틀림 정도를 달리하며 다양한 환경에서의 전류측정 실험을 행하였다. 실험결과로부터 광섬유 센서코일이 진동 등의 환경적 노이즈를 효율적으로 차단함을 알 수 있었으며 ±3% 이내의 시스템 출력안정도를 얻었다.

Universal Readout System for Temperature, Elongation and Hydrostatic Pressure Sensors Based on Highly Birefringent Fibers

In this paper, we present a universal readout system, which can be used to decode polarimetric fiber-optic sensors based on highly birefringent fibers. All such sensors use the same sensing principle, relying upon the dependence of modal birefringence on different physical parameters. To register the measurand-induced phase changes between polarization modes, we use the coherence-addressing principle. This requires that the interrogated sensor be powered by a broadband source (superluminescent diode) and that the total optical path delay introduced by the sensor be balanced in the decoding interferometer. The system performance in decoding elongation, temperature and hydrostatic pressure sensing is demonstrated.

Polarimetric fiber laser sensor for hydrostatic pressure

A polarimetric Fabry-Perot fiber laser sensor for fluid pressure up to 100 MPa is investigated. The fluid acts on one of two elliptical-core fiber sections in the laser cavity, producing a shift in the differential phase of the two orthogonal polarization modes and thus a variation in the beat frequencies of the corresponding longitudinal laser modes. The second fiber section, with a 90 degrees offset in the core orientation, compensates for temperature-induced phase shifts. The dispersion in the birefringent fiber Bragg grating reflectors is employed to remove the near degeneracy of the polarization mode beat frequencies of a given order and to improve substantially the resolution of the sensor to a few parts in 10(6) of the free spectral range. Further investigations address the effect of the fluid on the integrity of the fiber, the influence of various fiber coatings on the sensor response, and the intrinsic stability of erbium-doped and undoped sensing fibers under fluid pressure.

Land use mapping with evidential fusion of features extracted from polarimetric synthetic aperture radar and hyperspectral imagery

Abstract As part of the Earth Observation Application Development Program (EOADP) program sponsored by the Canada Space Agency, Lockheed Martin Canada––in partnership with Defense Research and Development Canada––has initiated a study aiming at studying the exploitation of the synergy between polarimetric SAR and hyperspectral imagery with the development of a system prototype called Intelligent Data Fusion System (IDFS). This system, based on the evidential fusion of features extracted from each type of imagery, is made of three modules. The polarimetric SAR module contains polarimetric classifiers, textural classifiers to provide hypotheses related to the textural and scattering properties of the illuminated area. The hyperspectral module contains an end-members selection technique and a collection of spectral indices. Each feature giving an incomplete representation of an object of interest, it is expected that the combination of complementary, redundant features will contribute to reduce the false alarm rate, improve the confidence in the target identification and the quality of the scene description as a whole. The combination of information provided by each feature extractor is performed according to the theory of evidence (Dempster–Shafer) in the third module. This paper presents an overview of the current functionality of IDFS. First results of evidential fusion are shown for land use mapping. Data sets were acquired over Indian-Head (Saskatchewan) with an airborne C-band polarimetric SAR and HSI Probe-1 sensors and were provided by the Canada Center for Remote Sensing.

Determination of solid materials rigidity modulus by a new nondestructive optical method

We propose a new optical method for the determination of the rigidity modulus G of solid materials. The rigidity modulus is determined by measuring the twisted angle θ as a response of the material sample, depending on the applied force. The measuring of this twisted angle can be carried out by using an adapted polarimetric sensor. The effective measurement of rigidity modulus G for aluminum, Plexiglas and steel was experimentally obtained 1.4464×10 10,0.99417×10 9 and 1.0395×10 11 N m , respectively. The study has demonstrated the effective usefulness of our method for evaluating the rigidity modulus. A good agreement between the theoretical and experimental results was achieved.

Imaging multispectral polarimetric sensor: single-pixel design, fabrication, and characterization.

A discrete-component approach was taken to establish the operational feasibility of a novel, imaging, midinfrared, multispectral, polarimetric sensor for remote-sensing application. The sensor is designed to exploit the spectral and polarimetric characteristics of the scene as discriminants. Pixelated multispectral filters and polarization filters were designed and fabricated on sapphire and Si substrates, respectively, and both were characterized. A single-pixel spectropolarimetric composite filter was characterized by use of a Fourier transform infrared spectrometer and a Pt-Si thermal-imaging camera. The experimental results show excellent agreement with theoretical predictions.

Dispersion effects in a highly birefringent fiber laser sensor with fiber Bragg grating reflectors

The effects of dispersion in the highly birefringent fiber Bragg grating reflectors of a polarimetric elliptical-core fiber laser sensor are experimentally and theoretically investigated. The laser sensor is designed to measure fluid pressure. It is experimentally and theoretically shown that the wavelength-dependent phase shifts in the gratings can be employed to remove the near degeneracy of the polarization mode beat frequencies of a given order, which substantially improves the resolution of the sensor. A resolution of a few parts in 10(6) of the free spectral range of the laser is demonstrated.

Structural health monitoring using a fiber optic polarimetric sensorand a fiber optic curvature sensor - static and dynamic test

In this paper, a fiber optic polarimetric sensor (FOPS) and a fiberoptic curvature sensor (FOCS), for global health\\damage monitoringof an aluminum specimen with different cracks, are theoretically andexperimentally analyzed. The relation between the sensor sensitivity and thespecimen stiffness is given and a static damage factor (SDF) is introducedto describe the stiffness reduction of the specimen. Based on this parameter,the experimental results show that the two sensors can be used as quantitativedamage indicators for the global health monitoring of structures. The dynamicdamage factor (DDF) is also introduced to describe the damage level ofcracked beams. The relation between DDF and the frequency of nth mode isdeduced. The experimental results from FOPS show that the DDF is an alternatemeasure of the damage and is shown to be similar to the SDF.