Abstract: A detection system for measuring glass that has been placed under strain and the resulting stress lines in the glass has a light source of individual elements configured to create a light distribution. The light distribution has a discontinuity which enhances the viewing of a photoelastic effect in the glass. The light source creates a viewable optical interference (i.e., color changes) which results from stress lines in the glass.

Abstract: An imaging polarimeter includes a polarization dispersing element, a spatial light modulator, a complementary polarization dispersing element, a polarization analyzer, an electronic detection plane, and a processor. The polarization dispersing element polarimetrically disperses an image of an object. The spatial light modulator spatially modulates the polarimetrically dispersed image. The complementary polarization dispersing element polarimetrically combines the spatially modulated and polarimetrically dispersed image. The polarization analyzer mixes orthogonal input polarizations with the polarization states of the polarimetrically combined spatially modulated image. The electronic detection plane measures the polarimetrically combined spatially modulated image that includes mixed polarization states.

Abstract: A short-pulse measurement and detection apparatus utilizing an aperiodic non-linear quasi-phase matched (A-QPM) material. The bandwidth of the A-QPM non-linear material is such that an interaction between a first signal and a second signal occurs, facilitating measurements of signal properties by techniques such as intensity auto-correlation, intensity cross-correlation, and pulse sampling.

Abstract: A method and a configuration for the depth-resolved optical detection of a specimen, wherein a specimen or a part of the specimen is scanned by means of preferably linear illumination, the illumination of the specimen is periodically structured in the focus in at least one spatial direction, light coming from the specimen is detected and images of the specimen are generated, and at least one optical sectional image and/or one image with enhanced resolution is calculated through the specimen is calculated [sic], images are repeatedly acquired and sectional images are repeatedly blended while changing the orientation of the linear illumination relative to the specimen and/or spatial intervals between from lines exposed to detection light from the illuminated specimen region are generated for the line-by-line non-descanned detection on an area detector or a camera and/or, during a scan, light is further deflected upstream of the detector through the line in the direction of the scan of the specimen.

Abstract: A system and method for biomolecular sensing are disclosed. The system includes a receptor for a target, a source of p-polarized light positioned to direct light toward the receptor in a manner effective to result in a condition of near perfect interference in the absence of target binding; and a detector positioned to measure any light reflected from the front and back surfaces of the coating. The receptor includes a substrate and a translucent coating on the substrate having front and back surfaces, wherein the incident angle for one of the substrate/coating interface and the medium/coating (probe) interface is greater than its Brewster angle and the incident angle for the other interface is less than its Brewster angle.

Abstract: Systems and methods for measuring a pulse length (?0) of an ultra-short light pulse (P0) based on processing a number of substantially similar light pulses. The system includes an autocorrelation optical system adapted to receive the light pulses P0 and create from each light pulse two beams having an associated optical path length difference ?OPL. Providing a different ?OPL for each light pulse creates an autocorrelation interference pattern representative of an autocorrelation of the light pulse P0. An LED detector detects the autocorrelation interference pattern and generates therefrom an autocorrelation signal. A signal-processing unit forms from the autocorrelation signal a digital count signal representative of a number of counted peaks in the autocorrelation signal above the full-width half maximum. Control electronics unit causes the varying ?OPL and provides a difference signal (S?) representative of the ?OPL to the signal-processing unit.

Abstract: An approach to diagnosing various physiological conditions in a subject entails determining the presence and, optionally, the amount or concentration of cell-free DNA in a sample from the subject. For this purpose one can employ an element that includes an optical surface with DNA-binding molecules immobilized thereon, where the optical surface is adapted for an optical instrument configured to detect DNA bound by the surface-immobilized molecules. Accordingly, one can diagnose in the subject a disease or other physiological condition by (A) contacting a sample from the subject with DNA-binding molecules and then (B) determining optically whether DNA has bound to the DNA-binding molecules, consequent to contacting the sample.

Abstract: A method and apparatus for accurately retrieving the position of an optical feature. The method uses the optical properties of biaxial crystals to conically refract the optical feature and transform the image of the optical feature to a circular ring structure. The position of the optical feature is then calculated by locating a center point associated with the circular ring structure.

Abstract: In one aspect, the disclosure features methods that include using a microscope to direct light to a test object and to direct the light reflected from the test object to a detector, where the light includes components having orthogonal polarization states, varying an optical path length difference (OPD) between the components of the light, acquiring an interference signal from the detector while varying the OPD between the components, and determining information about the test object based on the acquired interference signal.

Abstract: An interferometer has a first reflective surface having a nominal orientation; a second reflective surface having a nominal orientation orthogonal to the nominal orientation of the first reflective surface; a retroreflector facing the first reflective surface; a double polarizing beam splitter (DPBS) between the first reflective surface and the retroreflector; and a respective quarter-wave plate between the DPBS and each of the reflective surfaces. The DPBS has first and second beam-splitting surfaces each having a nominal orientation with respect to the first reflective surface. At least part of at least one of the first reflective surface, the second reflective surface and the beam-splitting surfaces is effectively tilted relative to the respective nominal orientation of such surface, and constitutes a respective tilted surface.

Abstract: Exemplary embodiments of detection and transmission arrangements are disclosed herein. For example, some of the disclosed embodiments comprise a splitter, a detector, first and second paths defined between the splitter and the detector, and a manipulation arrangement. In certain embodiments, the splitter is arranged to direct an incoming particle along the first or second path depending upon the value of a parameter of the incoming particle. In particular embodiments, the manipulation arrangement is located on at least one of the first and second paths, so that, if a particle in a superposition of values of the parameter impinges on the splitter and a wavefunction of the particle is directed along both the first and second paths, the manipulation arrangement will act on the wavefunction to allow interference, at or near the detector, between the portions of the wavefunction that were directed along the first and second paths.

Abstract: An apparatus and method for detecting a PMUX multilevel DPSK signal having at least two polarization components with equal symbol periods, which comprises utilizing two polarization-independent Optical Delay Interferometers (ODIs), detecting the four outputs of the two ODIs with two balanced detectors, and digitizing the two detected electronic signals at a sampling rate of twice the symbol rate of the said polarization component signals.

Abstract: An optical characteristic measuring apparatus includes: a light source section which sweeps wavelengths of a first input light and a second input light respectively, frequencies of the first and second input lights being different from each other and polarized states of the first and second input lights being perpendicular to each other, and outputs the first and second input light; an interference section which inputs one branched light of the first and second input lights to a measuring object, makes output light from the measuring object interfere with other branched light of the first and second input lights, and outputs a plurality of interference lights; a plurality of light receiving sections which are respectively provided for the interference lights, receives the interference lights respectively, and outputs signals in accordance with optical powers of the interference lights respectively; and a low-pass filter for filtering the outputted signals.

Abstract: In a defect inspecting apparatus, a differential interference optical system forms a differential interference image which is produced from an optical interference of images in a predetermined direction, the images corresponding to inspecting parts of a pattern formed on a mask. A control part varies the predetermined direction so as to cause the differential interference optical system to produce another differential interference image. An image pickup sensor picks up the differential interference images in accordance with the variation of the predetermined direction. A defect detecting unit detects a defect in the pattern formed on the mask from comparing the differential interference images with reference images, respectively.

Abstract: The present invention provides a measurement apparatus comprising a first polarization control unit configured to control a polarization state of light which enters an optical system to be measured to at least two different polarization states, a wavefront splitting unit which is inserted between the first polarization control unit and the optical system, a second polarization control unit which is inserted between the optical system and an image sensor, includes a phase plate, and is configured to control the polarization state of the light, and a processing unit configured to calculate the optical characteristics of the optical system, based on a plurality of interference patterns sequentially sensed by the image sensor by rotating the phase plate.

Abstract: Interference measurements obtained by comparison of a same beam (i.e. same nominal polarization, intensity, coherence length and wavelength) striking a same region on a sample at a same angle, but having a different beam wavefront upon intersection with the region are shown to provide images with independent coherent speckle noise patterns. Accordingly a plurality of interference measurements with diverse beam wavefronts can be used to identify or reduce coherent speckle noise. Reduction of the coherent speckle noise can be performed by compounding the aligned images. A change in the beam wavefront may be provided by displacing the sample in the direction of the beam between or during the measurements, when the beam is a focused beam (i.e. converging or diverging).

Abstract: An apparatus and a method of polarization dependent analyzation of an optical signal transmitted through a DUT includes splitting the optical signal into a first signal part having an initial first polarization and a second signal part having an initial second polarization, coding the first signal part using a first code and coding the second signal part using a second code, providing the coded signal parts to the DUT, detecting a DUT-signal coming from the DUT in response to the coded signal parts, and determining a first part of the DUT-signal corresponding to the first signal part by means of the first code and determining a second part of the DUT-signal corresponding to the second signal part by means of the second code.

Abstract: The disclosed technology provides a dynamic interconnection system which allows to couple a pair of optical beams carrying modulation information. In accordance with the disclosed technology, two optical beams emanate from transceivers at two different locations. Each beam may not see the other beam point of origin (non-line-of-sight link), but both beams can see a third platform that contains the system of the disclosed technology. Each beam incident on the interconnection system is directed into the reverse direction of the other, so that each transceiver will detect the beam which emanated from the other transceiver. The system dynamically compensates for propagation distortions preferably using closed-loop optical devices, while preserving the information encoded on each beam.

Abstract: Systems configured to provide illumination of a specimen or to inspect a specimen are provided. One system includes a light source configured to generate pulses of light at a repetition rate. The system also includes optical elements arranged in a first interferometer configuration followed by a second interferometer configuration. The optical elements are configured to quadruple the repetition rate of the pulses of light. In addition, the system includes an electro-optic phase modulator configured to receive the pulses of light from the optical elements and to alter a polarization of the pulses of light at a rate of one half the quadrupled repetition rate such that the pulses of light can be directed to the specimen as effectively continuous-wave uniformly polarized illumination.

Abstract: A back-end assembly for use with a front-end assembly in acquiring phase-shifted interferograms having a plurality of imaging modules (Ma, Mb, Mc). Each module (Ma, Mb, Mc) has a quarter wave plate (30a, 30b, 30c), a polarizer (32a, 32b, 32c), and an image sensor (34a, 34b, 34c) so that each polarizer has a different rotation orientation thus acquiring phase-shifted interferograms.

Abstract: An optical measuring apparatus, includes an optical branch element for splitting a measured light into plural lights, a time delay processing portion for giving a predetermined time delay to one split light of the measured light, an optical phase diversity circuit for outputting an in-phase signal component and an quadrature-phase signal component of the measured light by virtue of an interference between the measured light and a reference light between which a relative time difference corresponds to a time give by the time delay, while using other split light of the measured light or the measured light to which a process is applied by the time delay processing portion as the reference light, a data processing circuit for calculating at least one of an amount of change of an amplitude and an amount of change of a phase of the measured light, based on the in-phase signal component and the quadrature-phase signal component, and an optical time gate processing portion or an electric time gate processing portion

Abstract: An optical characteristic measuring apparatus includes: a light source section which sweeps wavelengths of a first input light and a second input light respectively, frequencies of the first and second input lights being different from each other and polarized states of the first and second input lights being perpendicular to each other, and outputs the first and second input light; an interference section which inputs one branched light of the first and second input lights to a measuring object, makes output light from the measuring object interfere with other branched light of the first and second input lights, and outputs a plurality of interference lights; a plurality of light receiving sections which are respectively provided for the interference lights, receives the interference lights respectively, and outputs signals in accordance with optical powers of the interference lights respectively; and a low-pass filter for filtering the outputted signals.

Abstract: A method for characterizing a device under test includes propagating multiple optical signals through the device under test and combining the multiple optical signals with a reference optical signal. The multiple optical signals are mixed with the reference optical signal and a relative perturbation between the multiple optical signals from the mixing of the multiple optical signals with the reference optical signal is determined. In another embodiment a modulated optical signal is provided from a local oscillator and the modulated optical signal is combined with the input optical signal. The modulated optical signal is mixed with the input signal to provide a mixed signal and at least one polarization-resolved parameter of the input optical signal is extracted from the mixed signal.

Abstract: A passive optical system substantially simultaneously separates light received at an optical input into three or more output light beams on optical outputs. The output light beams may have intensities that are proportional to intensities of optical projections of the received light onto three or more basis vectors of a tetrahedral basis set of a Stokes space. The system includes either multiple partial polarization splitters or multiple optical interferometers.

Abstract: A polarization sensitive spectral interferometer apparatus and method for analyzing a sample. The polarization sensitive spectral interferometer apparatus and method determines polarization properties of the sample.

Abstract: The present invention relates to an imaging apparatus and comprises input and output polarisers, a first polarising beam splitter and at least one additional polarising beam splitter, a light sensitive detector and focussing means arranged on an axis. The input polariser resolves incident light into a single linear polarisation state. The first polarising beam splitter receives light from the input polarises, and resolves it into equal magnitude orthogonally polarised rays which are mutually spaced and have a path difference therebetween. The or each additional polarising beam splitter is arranged to receive light from the first polarising beam splitter. The transmission axis of the output polariser is parallel to or perpendicular to the transmission axis of the input polarises to resolve the orthogonally polarised light rays having past through the or each additional polarising beam splitter into the same or perpendicular polarisation state as light resolved by the, first polariser.

Abstract: The invention relates to a polarization maintaining optical delay circuit (1) for providing a time delay to an incident light (S1), comprising an optical directional element (11) adapted for directing an incident light (S1) from a first port (111) to a second port (112) and directing a returning light from the second port to a third port (113), a mirror element (12) adapted for reflecting the incident light (S1), thereby changing the polarization state, so that the returning light (S2) has a substantially orthogonal polarization state compared to the polarization state of the incident light (S1), and an optical waveguide (13) adapted for optically connecting the second port (112) of the optical directional element (11) and the mirror element (12). The invention also relates to a ring cavity (2,3) comprising such an optical delay circuit, and an optical interferometer (4,5) with said optical delay circuit.

Abstract: The invention relates to a device, for measuring the contrast of fringes in a Michelson interferometer at full field, comprising a Wollaston prism for diverting two perpendicular incident polarisations into two different emergent directions, said diverting means being arranged within the interferometer as substitute for a single polariser. The device is of application to a Michelson interferometer used in an OCT tomographical system and comprising means for obtaining interferometric contrast without use of a modulation technique or synchronous detection methods.

Abstract: An interferometric optical analyzer apparatus comprises a light source, an interferometer and a detection system for determining the linear response, and subsequently any optical parameter, of one or more optical elements using substantially unpolarized light. In one embodiment, the light source supplies substantially unpolarized coherent light over a predetermined range of optical frequencies. The optical element is coupled in one arm of the interferometer and the other arm of the interferometer is used as a reference. The unpolarized light is first passed through the interferometer then through a three-way polarization splitter unit to split the light into at least three light beams according to preselected polarization axes corresponding to three linearly independent states of polarization. The three light beams are coupled to individual detectors and a controller computes Jones matrix elements from the resulting electrical signals.

Abstract: Methods and compositions are provided for detecting biomolecular interactions. The use of labels is not required and the methods can be performed in a high-throughput manner. The invention also provides optical devices useful as narrow band filters.

Abstract: A vibration detection device includes: a light source emitting a laser beam; an interferometer including a first vibrating body and a second vibrating body both capable of reflecting the laser beam, the interferometer splitting the laser beam into beams traveling along first to third optical paths, and the interferometer causing interference between a first reflected beam reflected by the first vibrating body in the first optical path and a reference beam passing through the third optical path to form a first interference pattern, and causing interference between a second reflected beam reflected by the second vibrating body in the second optical path and the reference beam to form a second interference pattern; and a detection means quantizing the vibrations of the first and second vibrating bodies on the basis of the formed first and second interference patterns to detect the vibrations.

Abstract: Disclosed is an optical sensing device including a source unit providing a beam of light with continuously modulated phase retardation between p- and s-polarization components of the light by employing a LCM; a reference unit receiving a first part of the light to provide a reference signal; a SPR sensing unit receiving a second part of the light to induce a phase retardation change between the p- and s-polarization components due to SPR associated with a sample; a probe unit receiving the light after SPR to provide a probe signal; and a detection unit connected to the reference unit and the probe unit to detect characteristics of the sample by comparing the reference signal with the probe signal. By using active phase modulation technologies and differential phase measurement, it is possible to fulfill chemical and biological detection.

Abstract: Provided herein are systems, methods, and compositions for optical coherence tomography implementations.

Abstract: A heterodyne optical signal analyzer (HOSA) permits accurate reconstruction of an optical input signal (Es) in the time domain. In one embodiment, a vector representation of the light is used to account for two polarization states of the optical signal. The components of a heterodyne optical signal analyzer (10), including optical couplers (12), all have errors and offsets. For example, optical power detectors (16) are very sensitive to changes in polarization of the optical signal (Es) and of the reference signal (Er). Several HOSA calibration procedures including detector calibration, vector calibration, and reference signal calibration are described.

Abstract: A method and apparatus for determining the optical parameters of a device under test (DUT) is disclosed. A first portion of an optical signal is modulated to generate a first modulated signal. The first modulated signal is applied to the DUT to output a test signal. A second portion of the optical signal is modulated to create a reference signal. The test signal and reference signal are optically combined into a combined signal. An electrical signal generated from the combined signal is processed to determine at least one optical parameter of the DUT. Processing the electrical signal includes demodulating the electrical signal.

Abstract: A polarization control system includes a light source that generates two light beams with different polarization states and optical frequencies. A polarization state modulator changes the polarization states of the two light beams. A first detector path generates a first beat signal from the two light beams passing through a first polarizer. A second detector path generates a second beat signal from the two light beams passing through a second polarizer that is oriented substantially orthogonal to the first polarizer. An amplitude detector generates an amplitude beat signal from the first and the second beat signals. The system then uses the amplitude beat signal to determine how to adjust the polarization state modulator in order to generate the first and the second light beams with the desired polarization states.

Abstract: A method and apparatus that uses specific source modulation and detectors to detect a response that carries information about a system response matrix associated with each sensor in a interferometric sensor array and extracting a sensor response in a manner that eliminates polarization-induced signal fading and that is insensitive to lead fiber birefringence fluctuations.

Abstract: Quantum resonance fluorescent microscope systems for detecting component substances in a specimen are described. The systems are based on exciting the sample containing the material with a femtosecond to nanosecond probe pulse of collimated light, which is tailored to optimize detection of a given material by separating the probe pulse into component features of frequency, polarization, phase and/or amplitude. The component features are independently shaped and formed into a composite pulse selected to optimize a signature response pulse received from the material. In some cases, two independently re-shaped pulses are combined, where one re-shaped pulse has two mixed polarization states and the other re-shaped pulse is linearly polarized. These two pulses are made to intersect at an angle of 90 degrees so that the combined pulse has electric field in each of the XYZ axes.

Abstract: The present invention relates to a new model for interpreting interferometric measurements, able to lead to a new method, system (10) and device (27) for measuring the PMD (Polarisation Mode Dispersion) of an optical fibre (11). The model, which is based on the theory of propagation of the optical signal as can be determined according to the socalled Prindpal States of Polarisation (PSPs) of the fibre, leads to a new interpretation of the interferogram generated with the interferometric measurements and is characterized in that it identifies in said interferogram a central peak and two side lobes. Thanks to this new model, it is possible to determine the PMD of the fibre based on the information content associated to at least one of the two side lobes identified in the interferogram.

Abstract: The present invention relates to an apparatus and to a method of load dependent analyzing an optical component (114), comprising the steps of: splitting an initial signal (115) into the reference signal (115b) into and into a measurement signal (115a), intermittently providing a load signal (108) to the component (114), providing the measurement signal (115a), to the component (114),so that the component (114) can influence the measurement signal (115a) to create a signal (120) influenced by and received from the component (114), superimposing the reference signal with the signal (120) received from the component (114), to provide a superimposed signal (118), detecting the superimposed signal (118) when the loading signal (108) is not present at the component (114) to provide an information containing signal (126), and processing the information containing signal (126) to determine an optical property of the component (114) dependent on a property of the load signal (118).

Abstract: An exposure apparatus includes an interferometer which forms interference fringes including aberration information on projection optics using polarized light beams emitted from an illumination system, and a processor which calculates the optical characteristics of the projection optics on the basis of interference patterns sequentially formed by the interferometer using at least three different polarized light beams sequentially generated by a polarization controller. The optical characteristics include unpolarization aberration which does not depend on the polarization state of light entering the projection optics, and polarization aberration which depends on the polarization state of the light entering the projection optics.

Abstract: The present invention integrates the surface plasmon resonance and common-path phase-shift interferometry techniques to develop a microscope for measuring the two-dimensional spatial phase variation caused by biomolecular interactions on a sensing chip without the need for additional labeling. The common-path phase-shift interferometry technique has the advantage of long-term stability, even when subjected to external disturbances. Hence, the developed microscope meets the requirements of the real-time kinetic studies involved in biomolecular interaction analysis. The surface plasmon resonance microscope of the present invention using common-path phase-shift interferometry demonstrates a detection limit of 2×10?7 refractive index change, a long-term phase stability of 2.5×10?4? rms over four hours, and a spatial phase resolution of 10?3 ? with a lateral resolution of 100 ?m.

Abstract: In a method for measuring an absorption coefficient and a reduced scattering coefficient of a multiple scattering medium, a source light beam is outputted, and is transformed into a transformed light beam that includes a mutually parallel circularly polarized photon pair. The transformed light beam is split into a signal beam, which is focused and projected into the multiple scattering medium to produce a diffused polarized photon pair density wave, and a reference beam, which is converted into a reference heterodyne interference signal. The diffused polarized photon pair density wave is converted into a test heterodyne interference signal. Amplitude attenuation and phase delay of the signal beam that has propagated through the multiple scattering medium is obtained based on the reference and test heterodyne interference signals, from which the absorption coefficient and the reduced scattering coefficient of the multiple scattering medium are inferred.

Abstract: A system and method for analyzing the characteristics of a thin film is provided whereby the in-plane birefringence of thin films is determined by measuring the interference fringes in the transmission or reflection spectra using unpolarized light and light linearly polarized along the MD and CD directions. The three spectra can be measured simultaneously or sequentially. The in-plane birefringence data can be used to characterize clear polymer films, which are principally made of biaxial oriented polymer, as the film is being continuously fabricated on a production line.

Abstract: A method and an apparatus for determining the influencing of the state of polarization of optical radiation by an optical system under test, wherein radiation with a defined entrance state of polarization is directed onto the optical system, the exit-side state of polarization is measured, and the influencing of the state of polarization is determined by the optical system with the aid of evaluation of the exit state of polarization with reference to the entrance state of polarization. An analyser arrangement which can be used for this purpose is also disclosed. The method and the apparatus are used, e.g., to determine the influencing of the state of polarization of optical radiation by an optical imaging system of prescribable aperture, the determination being performed in a pupil-resolved fashion.

Abstract: Arrangements and methods are provided for obtaining data associated with a sample. For example, at least one first electro-magnetic radiation can be provided to a sample and at least one second electro-magnetic radiation can be provided to a reference (e.g., a non-reflective reference). A frequency of such radiation(s) can repetitively vary over time with a first characteristic period. In addition, a polarization state of the first electro-magnetic radiation, the second electro-magnetic radiation, a third electro-magnetic radiation (associated with the first radiation) or a fourth electro-magnetic radiation (associated with the second radiation) can repetitively vary over time with a second characteristic period which is shorter than the first period. The data for imaging at least one portion of the sample can be provided as a function of the polarization state.

Abstract: A device for polarization-specific examination of an optical system having a detector part that has polarization detector means for recording the exit state of polarization of radiation emerging from the optical system. Also, an associated optical imaging system, and a calibration method for the device. The device includes a polarization detector with a polarizing grating structure. Provided as an alternative is a device for snapshot polarimetry having a birefringent element and downstream polarizer element that adequately polarizes nonquasi-parallel radiation. The device may be used for determining the influence on the state of polarization of UV radiation by a microlithographic projection objective.

Abstract: The invention concerns a tandem interferometer for temperature sensing. The low coherence interferometry (LCI) system comprises a polarization-based sensing interferometer comprising a birefringent crystal having a sensor temperature sensitivity and a birefringence dispersion, and a readout interferometer being either a Fizeau interferometer using an optical wedge or a polarization interferometer using a birefringent wedge. In one embodiment of the invention, the birefringent crystal has dispersion properties similar to that of the birefringent wedge or that of the optical wedge of the readout interferometer. The present invention also provides a signal processing method for correcting the dispersion effect and for noise filtering in LCI-based optical sensors of the tandem interferometer arrangement.

Abstract: The invention provides a method and a system for measuring a physical quantity by means of a tandem interferometer optical sensor system based on low-coherence interferometry. The system comprises a light system, a sensing interferometer and a polarization readout interferometer. The invention provides a polarization interferometer comprising a single birefringent wedge. The invention also provides for a dispersion-compensated optical sensor system. The invention also provides an interferometer sensitive to temperature that comprises a trajectory in a LiB3O5 crystal with an x-cut orientation.

Abstract: An optical fiber interferometer (10) with relaxed loop tolerance, and a quantum key distribution (QKD) system (200) using same is disclosed. The interferometer includes two optical fiber loops (LP1 and LP2). The loops have an optical path length (OPL) difference between them. A polarization-maintaining (PM) optical fiber section (60) of length (L60) and having fast and slow optical axes (AF and AS) optically couples the two loops. The length and fast-slow axis orientation is selected to introduce a time delay (?T1-2) between orthogonally polarized optical pulses traveling therethrough that compensates for the OPL difference. This allows for drastically relaxed tolerances when making the loops, leading to easier and more cost-effective manufacturing of the interferometer as well as related devices such as a optical-fiber-based QKD system.