554 results about "Faraday rotator" patented technology

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.

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.

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.

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 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.

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.

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 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.