559 results about "Faraday rotator" patented technology

An Optical Coherence Tomography (OCT) device irradiates a biological tissue with low coherence light, obtains a high resolution tomogram of the inside of the tissue by low-coherent interference with scattered light from the tissue, and is provided with an optical probe which includes an optical fiber having a flexible and thin insertion part for introducing the low coherent light. When the optical probe is inserted into a blood vessel or a patient's body cavity, the OCT enables the doctor to observe a high resolution tomogram. In a optical probe, generally, a fluctuation of a birefringence occurs depending on a bend of the optical fiber, and this an interference contrast varies depending on the condition of the insertion. The OCT of the present invention is provided with polarization compensation means such as a Faraday rotator on the side of the light emission of the optical probe, so that the OCT can obtain the stabilized interference output regardless of the state of the bend.

Systems and methods for optically determining casing collar and / or corrosion locations within boreholes, using the diffraction effect of Faraday crystals through which depolarized continuous light is transmitted within optical fibers.

A polarization independent (PI) interferometer design that can be built from standard optical components is described. Based upon a Michelson interferometer, the PI interferometer uses a 50 / 50 splitter and Faraday Rotator Mirrors (FM's). The interferometer achieves good optical characteristics, such as high extinction ratio (ER) and low insertion loss (IL). Lack of polarization sensitivity reduces interferometer construction tolerances and cost, enhances performance and utility, and expands the scope of interferometric based devices. Such characteristics can be used to construct flexible, high performance, polarization insensitive, multi-rate, self-calibrating, optical DPSK receivers, power combiners, optical filters and interleavers, all-optical switches, and cascaded interferometers. Since polarization is not maintained in standard fiber optic networks, a PI-DPSK receiver allows for use of more sensitive DPSK communications over fiber, without need for costly polarization control hardware. Other applications of PI interferometers include optical CDMA, secure communications, optical coherence tomography (OCT), and temporal gratings with ultra-precise timing.

An optical equalizer / dispersion compensator (E / CDC) comprises an input / output for receiving a multiplexed channel signal comprising a plurality of channel signals of different wavelengths. An optical amplifier may be coupled to receive, as an input / output, the multiplexed channel signals which amplifier may be a semiconductor optical amplifier (SOA) or a gain clamped-semiconductor optical amplifier (GC-SOA). A variable optical attenuator (VOA) is coupled to the optical amplifier and a chromatic dispersion compensator (CDC) is coupled to the variable optical attenuator. A mirror or Faraday rotator mirror (FRM) is coupled to the chromatic dispersion compensator to reflect the multiplexed channel signal back through optical components comprising the chromatic dispersion compensator, the variable optical attenuator and the optical amplifier so that the multiplexed channel signal is corrected partially for equalization and chromatic dispersion compensation with respect to each pass through these optical components. The E / CDC components may be integrated in a photonic integrated circuit (PIC) chip. In several embodiments, a photonic integrated circuit (PIC) chip comprises an input into the chip that receives at least one channel signal having experienced chromatic dispersion, a chromatic dispersion compensator (CDC) that separates the at least one channel signal into separate wavelength components over a free spectral range (FSR) spanning only a signal channel width and subjects the wavelength components to a phase shift to change the wavelength group delay in the wavelength components and that recombines the wavelength components to reconstitute the at least one channel signal, and an output from the chip for the recombined at least one channel signal having reduced chromatic dispersion compared to the same channel signal received at the chip input. The CDC device may include a tuning section to vary the phase shift of wavelength components as they propagate through the device. Such a CDC device may include a Mach-Zehnder interferometer (MZI) or a cascaded group of Mach-Zehnder interferometers, or at least one arrayed waveguide grating (AWG) or at least one Echelle grating.

In all-optical networks, high speed optical switching and routing becomes one of the most important issues for interconnecting the transport network layers. This invention describes novel polarization-independent high speed optical switches using a digital Faraday rotator, which can also be used for various other optical switching devices. The basic digital Faraday rotator device is composed of (a) a semi-hard or hard iron garnet based magneto-optic crystal having bi-stable magnetization states at zero external magnetic field. (b) a wire winding around the crystal for changing the magnetization states by pulsed current having both fast rise time and short duration. (c) a circuit generating the required current pulses with both polarities. After a driving current pulse excitation to set the magnetization direction, the high coercive force and high remnant squareness in the garnet-based crystal will maintain the saturation magnetization state in the crystal without the need of any external current or magnetic field to sustain the remnant state. The apparatus and the method disclosed in this invention effectively reduces the overall power consumption. By using this digital Faraday rotator device, the polarization independent 1x2 and 2x2 optical switches are designed and fabricated.

A polarization element and a polarization-sensitive optical isolator are integrated to form an integrated VOA. A preferred embodiment uses a liquid crystal cell as the polarization element to which is attached an optical isolator core of a first polarizer, Faraday rotator, and second polarizer. Voltage on the liquid crystal cell electrodes controls the amount of polarized light from the liquid crystal cell passing through the first polarizer and light in the opposite direction is blocked. The integrated VOA can be mounted within a laser device package so that the power of the source laser diode on the output fiber can be controlled and yet the laser diode is protected from light undesirably entering laser device package through the output fiber.

Systems and methods for analyzing the anatomy of a patient's eye with circular or rotated polarized laser beams, or with laser beams of different wavelengths are disclosed. One system includes a polarization beam-splitter and a quarter-wave plate, wherein the quarter-wave plate is configured to circularly rotate a laser beam received from a laser that is transmitted and passes through the polarization beam-splitter, and to transform a circularly rotated back-reflected beam to a linearly polarized laser beam that is perpendicular to the beam that was transmitted through the polarization beam-splitter. Substantially all of the back-reflected beam is directed to a photo-detector for analysis. A Faraday rotator subsystem may be substituted for a polarization beam-splitter. An optical system including a laser that generates a laser beam of a first wavelength for therapeutic treatment, and another laser that generates a laser beam of a second wavelength for measurement is also disclosed.

In all-optical networks, high speed optical switching and routing becomes one of the most important issues for interconnecting the transport network layers. This invention describes novel polarization-independent high speed optical switches using a digital Faraday rotator, which can also be used for various other optical switching devices. The basic digital Faraday rotator device is composed of (a) a semi-hard or hard iron garnet based magneto-optic crystal having bi-stable magnetization states at zero external magnetic field. (b) a wire winding around the crystal for changing the magnetization states by pulsed current having both fast rise time and short duration. (c) a circuit generating the required current pulses with both polarities. After a driving current pulse excitation to set the magnetization direction, the high coercive force and high remnant squareness in the garnet-based crystal will maintain the saturation magnetization state in the crystal without the need of any external current or magnetic field to sustain the remnant state. The apparatus and the method disclosed in this invention effectively reduces the overall power consumption. By using this digital Faraday rotator device, the polarization independent 1x2 and 2x2 optical switches are designed and fabricated.

The invention relates to an unbalanced interferometer based fiber bragg grating (FBG) demodulation system and method, belonging to the technical field of fiber optic sensing. The system sequentially passes through a superluminescent diode (SLD) or an amplified spontaneous emission (ASE) broadband light source, an optic isolator, a circulator or a coupler, and a fiber bragg grating and returns back to the circulator or the coupler, and then passes through the coupler, an unbalanced Michelson interferometer with two channels and a Faraday rotator mirror and returns back to an interferometer and the coupler or passes through a Mach-Zehnder interferometer with two channels and the coupler, wherein one channel of the interferometer is wound around a piezoelectric ceramic or an electrooptical modulator, and an acousto-optic modulator, finally passes through a dense wave division multiplexer and a photoelectric detector and is connected with an ARCTAN based PGC (Phase Generation Carrier) signal response demodulation module. The invention has the advantages; by adopting the combination of the an FBG sensor and ARCTAN-based PGC phase modulation, the system has high sensitivity, large dynamic range and good linearity, good response to an abrupt signal and easiness of multiplexing, low cost and easiness of implementing.

A polarization independent (PI) interferometer design that can be built from standard optical components is described. Based upon a Michelson interferometer, the PI interferometer uses a 50 / 50 splitter and Faraday Rotator Mirrors (FM's). The interferometer achieves good optical characteristics, such as high extinction ratio (ER) and low insertion loss (IL). Lack of polarization sensitivity reduces interferometer construction tolerances and cost, enhances performance and utility, and expands the scope of interferometric based devices. Such characteristics can be used to construct flexible, high performance, polarization insensitive, multi-rate, self-calibrating, optical DPSK receivers, power combiners, optical filters and interleavers, all-optical switches, and cascaded interferometers. Since polarization is not maintained in standard fiber optic networks, a PI-DPSK receiver allows for use of more sensitive DPSK communications over fiber, without need for costly polarization control hardware. Other applications of PI interferometers include optical CDMA, secure communications, optical coherence tomography (OCT), and temporal gratings with ultra-precise timing.

An integrated measurement system for measuring a plurality of parameters is disclosed. The integrated system includes a fiber Bragg grating (FBG) sensor configured for modulating a wavelength of an FBG input signal to provide an FBG output signal corresponding to an FBG parameter, a fiber Faraday rotator (FFR) sensor module configured for rotating a polarization and modulating an intensity of an FFR input signal to provide an FFR output signal corresponding to an FFR parameter, wherein the FBG sensor and FFR sensor module are coupled to provide an integrated system output signal, and a detection system configured for receiving the integrated system output signal and for using the integrated system output signal to obtain values associated with at least one FBG or FFR parameter.

Monostatic LIDARs use the same telescope to send the laser beam in atmosphere and to collect the backscattered echo. An important element of monostatic LIDARs is the optical separator between the emission and reception paths of the laser beam. By using a system made by a Faraday rotator in combination with two polarizing beam splitters suitably oriented, it is possible to achieve this separation with minimum losses with respect to prior systems using semi-reflective plates and / or polarizing beam splitters in conjunction with quarter-wave plates. The effectiveness of this system does not rely on the maintenance of the polarization status of the laser beam when backscattered by the atmosphere molecules and particles, neither on the reduction of the received laser power relatively to the transmitted one. The system is simple, compact, and can work at several wavelengths of the laser source.

An integrated isolator array is provided having a plurality of waveguides fabricated in a planar optical substrate, each waveguide having input and output sections. An isolator subassembly is received within a transverse trench formed in the substrate between the input and output sections such that it intersects the optical paths of the waveguides. The isolator subassembly, which may consist of layers of Faraday rotator material sandwiched between layers of birefringent crystal material, permits the forward passage of light from the input sections to the output sections of the waveguides while preventing the backward passage of light from the output to the input sections. Each waveguide input section is preferably adapted with a mode-expanding input taper to collimate light propagating through the waveguide. Similarly, each output section is preferably adapted with a mode-reducing output taper to reduce the mode size of forward-traveling light to match that of an output fiber, as well as to collimate light traveling backward within the output section.

An integrated photonic polarization-separating apparatus includes a first waveguide polarization beam splitter (PBS) having a first port, a second port, a third port, and a fourth port and a first polarization rotator optically coupled to the first port of the first waveguide PBS. The apparatus also includes a first Faraday rotator optically coupled to the first polarization rotator and a second polarization rotator optically coupled to the second port of the first waveguide PBS. The apparatus further includes a second Faraday rotator optically coupled to the second polarization rotator and a second waveguide PBS having a first port, a second port, a third port, and a fourth port. The third port is optically coupled to the first Faraday rotator and the fourth port is optically coupled to the second Faraday rotator.

The embodiment of the invention provides a light transceiving integrated device applied to fiber sensing. The light transceiving integrated device comprises a light source, a photoelectric detector, a polarizing beam splitter, a half-wave plate, a Faraday rotator, a reflector and a lens, wherein the polarization state of emergent light emitted by the light source is regulated through the half-wave plate and the Faraday rotator so that the emergent light is changed between parallel transmission light and vertical reflected light; and the emergent light after the polarizing regulation enters tail fibers of polarization maintaining fibers through the polarizing beam splitter, the reflector and the lens, and the emergent light is received through the photoelectric detector and returned from an interferometer sensor. The structure and the light path process can realize integration and encapsulation of discrete components in a single module, reduce the fiber welding point number in a fiber gyro system, eliminate the 6db inherent loss in the conventional system, and improve the reciprocity and stability of a fiber gyro.

Scanning apparatus which scans input radiation from a scene and output radiation is transmitted to a receiver system, for example a millimetre wave imaging camera or a radar receiver by a rotatable reflective plate having an axis of rotation passing through the centre of its surface, secondary reflector and static reflector, wherein the secondary reflector is a second rotatable reflective plate having a common axis of rotation with the first rotatable reflective plate, wherein the common axis of rotation is inclined at a non-zero zero angle thetab to the normal to the second reflective plate. The normal to the first rotatable plate is inclined at a small angle to the common axis of rotation, typically a few degrees and forms the secondary reflector. The static reflector may be a polarising roof reflector through which radiation is input to and output from the apparatus. The apparatus also includes a 45° Faraday rotator or a birefringent surface such as a Meander-line. An additional Faraday rotator and an inclined polariser may be included in the apparatus and arranged such that radiation output to the receiver system may be separated from the path of input radiation. Alternatively, the scanning apparatus may include a reflector lens arrangement, such that focused output radiation may be output directly to the receiver system.

The invention discloses an optical fiber watt transducer using a reflective quasi-reciprocal light path. Two schemes are provided, wherein one of the schemes is that optical fiber watt transducer comprises a light source, a first beam splitter, a polarizer, a phase modulator, a first delay optical fiber, a second beam splitter, a Faraday rotator, a voltage probe, a compensation optical fiber, a first reflector, a second delay optical fiber, a 1 / 4 wave plate, a current probe, a second reflector and a photoelectric detector; the another scheme is that the optical fiber watt transducer comprises the light source, the first beam splitter, an integrated phase modulator, a polarization beam splitter / combiner, the first delay optical fiber, the second beam splitter, the Faraday rotator, the voltage probe, the compensation optical fiber, the first reflector, the second delay optical fiber, the 1 / 4 wave plate, the current probe, the second reflector and the photoelectric detector. The optical fiber watt transducer disclosed by the invention has good capacity to resist environmental interferences such as temperature and vibration, is good in stability, low in noises, large in dynamic range and good in linearity, and can realize closed-loop detection.

The invention relates to a single-component fiber-optic geophone, a three-component fiber-optic microseismic geophone comprising the same and a three-component fiber-optic microseismic detection array also comprising the same, belongs to the technical field of fiber-optic sensors and aims to solve the problems that an unground system of the existing fiber-optic geophone is complex, the existing fiber-optic geophone is low in sensitivity and sensors are large in size. The single-component fiber-optic geophone is characterized in that two fiber Bragg gratings and a fiber coil form a fiber grating F-P (Fabry-Perot) cavity structure; sensitivity of the geophone is effectively improved. A faraday rotator mirror is replaced by low-reflectivity FBGs (fiber Bragg gratings) serving as a reflector; the structure is greatly simplified. In addition, compared with the traditional fiber Bragg grating with the F-P cavity, the single-component fiber-optic geophone has high sensitivity. The single-component fiber-optic geophone is applicable to microseismic monitoring.

Transparent heat-conductive layers of significant thickness are bonded or adhered to opposing optical faces of a Faraday optic to form a Faraday optic structure that can be used with beam-folding mirrors and an external magnetic field to form a multi-pass Faraday rotator with minimal thermal gradient across the beam within the Faraday optic. The transparent heat conductive layers conduct heat through the Faraday optic substantially parallel to the beam propagation axis for each pass through the Faraday optic structure and thereby reduce thermal gradients across the beam cross section that would otherwise contribute to thermal lens focal shifts and thermal birefringence in the Faraday optic structure. The multi-pass Faraday rotator of this invention is suitable for use with any device based upon the Faraday effect such as optical isolators, optical circulators and Faraday mirrors that are scalable with beam size to power levels in excess of 2 kW.

In one of embodiments of passive polarizing fiber optic gyroscope and current sensor, the core is a 3X3 ''round''polarization maintaining optic fiber coupler composed of ''round'' polarization maintaining fiber coupler. The coupler realizes light splitting and passive polarization effects simultaneously in Sagnac interference sensor optic fiber loop. A variable 3X3 hybrid optic fiber coupler is composed by two linear polarization maintaining optic fibers and a regular single mode optic fiber, wherein the tail fiber of the two linear polarization maintaining optic fibers are connected in interference optic fiber loop based on the linear polarization maintaining optic fiber, the two ends of the single mode optic fiber are cut into short sections by diagonal angles, in order to form matching end face on the two ends. In other embodiment of the passive polarizing fiber sensor, the core is an integrated Faraday rotator, comprising accurate magnetic-optic 45 degree rotation unit, of which one end is connected with a one-quarter glass of ''zero-to-rapid'' optic fiber, other end is connected with a one-quarter glass of ''rapid-to-zero'' optic fiber. The main merit of the passive polarization comprises: simple structure, working stability without manually tuning.

A dispersion compensation apparatus capable of compensating for dispersion while the state of polarization is maintained overall all channels between the input and output ends. Input signal light in alignment with the transmission polarization axis of a polarization beam splitter passes through the multiplexer and a wavelength dispersion-compensating device and is reflected by a Faraday rotator mirror so as to pass through the wavelength dispersion-compensating device again. Owing to the action of the Faraday rotator mirror, the signal light that returns to the wavelength dispersion-compensating device has a polarization that is orthogonal to the polarization that prevailed when the signal light first passed through the device. Thus the polarization beam splitter now operates in the reflective polarization mode with respect to the returning signal light. As a result, 100% of the signal light is output to a Polarization-maintaining optical fiber. Moreover, the polarization is fixed linear polarization.

Faraday rotator or isolator with mode stripping ferrules and collimators having fiber pigtailed mode stripping components. An example is a compact Faraday Isolator module employing mode stripping ferrules and mode stripping collimators at the input and / or at the output of a fiber pigtailed Faraday Isolator. Two basic isolator types are a Polarization Independent Faraday isolator and a Polarization Maintaining Faraday isolator. The device is substantially immune to damage due to back-reflection, thermal lensing, energy leakage and absorption. Mode stripped optical energy propagating in the reverse direction is diverted onto a heat absorbing and heat sinking structure, as for example at the input of a compact birefringent wedge-based PI isolator. Alternatively, the optical energy propagating in the reverse direction is angularly refracted away from the forward incident beam path and is coupled into the energy dispersive cladding of the input fiber or the ferrule itself.

The invention provides a system for improving the laser collimation precision by utilizing an optical phase conjugation principle, comprising a laser device, wherein a polarizer, a beam expanding and collimation system, a first beam splitter, a first polarization spectroscope and a reflector are sequentially arranged along an emitting light beam of the laser device; a position detector is arranged in a beam splitting direction of the first beam splitter; reflection light of the reflector is parallel to the emitting light beam of the laser device; a second polarization spectroscope, a Faraday rotator, a second beam splitter and a space optical phase modulating device are sequentially arranged on the reflection light of the reflector; a wave-front detector is arranged in the beam splitting direction of the second beam splitter; and the space optical phase modulating device and the wave-front detector are connected to a computer. The invention further provides a method for improving the laser collimation precision by utilizing the system; the system disclosed by the invention has a simple structure and influences of uneven atmosphere on the laser collimation can be effectively compensated; and the space optical phase modulating device is used as a phase conjugation mirror so that the system has the advantages of small size, easiness for controlling and the like.

The invention aims at designing a quantum key distribution network scheme that is easy to construct, enables the cost to be low, has high anti-interference capability, and is capable of realizing communication between any users and overcoming the defect caused by imperfect performances of parts of key devices. The provided scheme has the following advantages: firstly, combination of quantum channels, phase modulators, 90-degree faraday rotator mirrors is used, the birefrigent effect of the optical fiber and the optical device can be compensated automatically, the system stability is enhanced, and the anti-interference capability of the quantum key distribution system is improved; secondly, on the basis of the optical switch control, quantum key sharing between any two users in a network can be realized; thirdly, besides the master control side, each controlled side only needs one phase controller, faraday rotator mirror, and attenuator, so that the networking cost is substantially reduced; and fourthly, the master control side only serves as the auxiliary communication end in the network and will publish modulation information and detection results after communication completion, so that immunity to an attack strategy caused by the imperfect performance of the detector in the actual system can be realized.

The invention provides an optical coherence polarization measuring device capable of restraining interferential noises. The optical coherence polarization measuring device capable of restraining the interferential noises is composed of a high polarization stability broadband light source, an element to be detected, an optical path demodulator, a polarization crosstalk detector and a recording device. The optical path demodulator comprises a Faraday rotator for eliminating the optical interferential polarization fading effect and an optical circulator for detecting optical path difference, and polarization state controllers are arranged in front of the Faraday rotator and the optical circulator respectively. The polarization state of the transmitting light is adjusted to enable the polarization state of the input light to meet the minimum reflection condition under the Brewster angle, residue reflecting light signals in a device are reduced and eliminated, the optical interferential noises are restrained, and the polarization crosstalk measuring sensitivity is improved. The optical coherence polarization measuring device capable of restraining the interferential noises has the advantages of being high in measuring accuracy, wide in dynamic range, small in size, convenient to adjust, low in loss, and high in reliability, and can be applied to the optical performance quantitative test to high extinction ratio integration waveguide over 80 db and optical polarization devices.

The invention discloses a Faraday rotator suitable for a high-power opto-isolator. The Faraday rotator comprises a thermal compensation crystal, a half-wave plate, an iron ring, a first magnetic rotation crystal, a second magnetic rotation crystal, a first magnet and a second magnet. The first magnetic rotation crystal, the thermal compensation crystal, the half-wave plate and the second magnetic rotation crystal are laid out in the forward sequence of a Z axis, the iron ring is connected to the outside of the thermal compensation crystal and the outside of the half-wave plate in a sleeved mode, the first magnet is connected to the outside of the first magnetic rotation crystal in a sleeved mode, and the second magnet is connected to the outside of the second magnetic rotation crystal in a sleeved mode. When used for the opto-isolator, the Faraday rotator enables the opto-isolator to meet the requirement for high power of hundreds of watts and improves isolation degrees by at least 3dB.

The invention discloses an interferometry-based optical fiber Verdet constant measuring system. The system comprises an ASE (amplified spontaneous emission) light source, a single-mode optical fiber coupler, a Y-waveguide integrated optical modulator, 1 / 4 wave plates, Faraday rotator mirrors, a solenoid, a sine alternating-current driving circuit, matching fluid, a probe, an information processing module, a computer and measured optical fibers. The ASE light source, the single-mode optical fiber coupler, the Y-waveguide integrated optical modulator, the measured optical fibers and the Faraday rotator mirrors are connected through optical fibers in sequence. Each 1 / 4 wave plate is arranged between the Y-waveguide integrated optical modulator and the corresponding measured optical fiber. A signal processing portion comprises a feedback servo circuit, an FPGA (field programmable gate array) module and a phase modulation driving circuit. The system is of an all-optical-fiber structure and simple and convenient to set up; by the aid of the Faraday rotator mirrors, influences of linear birefringence of the optical fibers on measurement can be eliminated, and measurement accuracy is improved; and Verdet constants of various optical fibers can be measured by the system.

An optical apparatus and methods for operating on a polarization state of a light beam using a compound tri-state non-reciprocal rotator having two Faraday rotators. A first Faraday rotator rotates the polarization state into one of two partially rotated states at angles +α, −α, where α=22.5°, and the second Faraday rotates the polarization state from one of the partially rotated states into one of three fully rotated states at angles +2α, 0, −2α. A polarization selection mechanism guides light in the three fully rotated states differently to enable various devices and different modes of operation. For example, the polarization selection mechanism can generate a tri-state output in the form of two distinct output beams corresponding to two of the three fully rotated states, and an overlapping pair of output beams obtained when the compound tri-state non-reciprocal rotator produces the third of the three fully rotated states. The various methods permitted by the invention permit simple and cost-effective multicasting switches and methods.

The invention relates to a downhole optical fiber distributed flow monitoring system. The downhole optical fiber distributed flow monitoring system comprises an ultra-narrow line width laser, wherein laser light passes through an acousto-optic modulator, a first light amplifier and an ultra-narrow bandwidth first light filter, then enters a first circulator and then is filled into sensing optical fibers, and Rayleigh back-scattering light in the sensing optical fibers returns back to the first circulator, passes through a second light amplifier, enters an ultra-narrow bandwidth second light filter, passes through a polarization controller, enters a second circulator, then enters a 3x3 coupler, is split into a first faraday rotator mirror, a second faraday rotator mirror and a fourth photoelectric detector; the fourth photoelectric detector feeds electric signals into an optical fiber distributed flow demodulation system; the Rayleigh back-scattering light passes through the 3x3 coupler and enters a second photoelectric detector, a third photoelectric detector and the second circulator, and the second circulator outputs light signals to a first photoelectric detector; the first photoelectric detector, the electric signals of the second photoelectric detector and the third photoelectric detector simultaneously arrive at the optical fiber distributed flow demodulation system.