71 results about "Sagnac loop" patented technology

A source and / or method of generating quantum-correlated and / or entangled photon pairs using parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550 nm fiber-optic communication band and detected by a detection system including InGaAs / InP avalanche photodiodes operating in a gated Geiger mode. A generation rate>103 pairs / s is observed, a rate limited only by available detection electronics. The nonclassical nature of the photon correlations in the pairs is demonstrated. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks. The detection system also provides high rate of photon counting with negligible after pulsing and associated high quantum efficiency and also low dark count rate.

The invention relates to a device and a method for generating microwave signals by using a multi-wavelength Brillouin laser. An existing device obtains a high frequency difficultly. The device of the invention comprises an adjustable narrow-band light source, two isolators, three couplers, an erbium-doped optical fiber amplifier, two optical fiber circulators, a Sagnac loop mirror, an optical fiber Bragg grating and a photodetector. The adjustable narrow-band light source is in optical connection with the isolators; the isolators are in optical connection with the couplers; outputs of the couplers are in optical connection with another coupler respectively; one of optical paths is provided with the erbium-doped optical fiber amplifier, the two optical fiber circulators and the Sagnac loop mirror. The method for generating the microwave signals by using the device comprises the following steps that: pump spectrum light emitted by the adjustable narrow-band light source is split into two paths of pump spectrum light after passing through the isolators and the couplers, one path of the pump spectrum light performs beat frequency with the other path of the pump spectrum light after outputting single-channel high-order Stocks light so as to obtain high-frequency microwave signals. The device and the method change the wavelength of the pump spectrum light to make a multi-wavelength pass band continuously adjustable.

We have demonstrated a novel Sagnac loop and micro-ring based laser cavity which is simple and reliable, with accurately controlled reflectivity and negligible excess loss. The resonant wavelength of a 2 μm radius micro-ring is shown to be lithographically controlled to a standard deviation of 3.6 nm. Both C- and O-Band lasers based on Sagnac loop mirror and micro-ring cavity have been demonstrated. The lasers are shown to be able to be modulated at 40 Gb / s.

The invention relates to a method and a device for measuring an optical fiber length with high precision and large range. An acoustooptic modulator is connected with a Sagnac loop. The acoustooptic modulator is asymmetrically arranged in the Sagnac loop. One end of the optical fiber the length of waiting to be detected is connected with the Sagnac loop by a three-port 3-dB optical fiber coupler and the other end is a free end which can generate end surface reflection; the acoustooptic modulator is driven by a RF signal with variable frequency; when the frequency of the RF signal is changed, the transmittivity of the Sagnac loop is changed; the change of the transmittivity is relevant with the length of the optical fiber to be measured; the change of the transmittivity is measured by a photodiode; the output end of the photodiode is connected with a data collection card; the data collected by the collecting card is transmitted to a computer. The length of the optical fiber to be measured is obtained by fast Fourier change and relevant operations. The method and the device for measuring an optical fiber length with high precision and large range overcome the defects of being incapable of simultaneously meeting the demand of measuring with high precision and large range and having a relative lower cost. As the optical fiber to be measured is connected with the Sagnac loop, the anti-external temperature fluctuation and the mechanical anti-disturbance performances of the device are high.

The invention relates to a fiber Sagner loop dynamic weighing sensor. In the sensor, a tail fiber of a light source module is connected with a first port of a fiber circulator; a second port of the fiber circulator is connected with a first port of a fiber coupler; a third port and a fourth port of the fiber coupler are connected to form a loop circuit by fibers; a fiber polarization controller, a fiber protection and enhancement sensing head and a piezoceramics actuator are connected in series to the loop circuit; a third port of the fiber circulator is connected with an input terminal of a first photodetection unit; a second port of the fiber coupler is connected with an input terminal of a second photodetection unit; an output terminal of the first photodetection unit is connected with a data acquisition card; an output terminal of the second photodetection unit is connected with the data acquisition card; the data acquisition card is connected with an input terminal of the piezoceramics actuator to form a feedback loop and connected with a signal processing and displaying system. The fiber Sagner loop dynamic weighing sensor has the characteristics of strong environmental intrusion resisting capacity, high measuring precision and accuracy and wide measuring scope.

The invention discloses a tunable microwave photonic filter based on a photoinjection semiconductor laser system. The tunable microwave photonic filter comprises a master laser, a first polarization controller, a variable optical attenuator, an optical circulator, a slave laser, a second polarization controller, a third polarization controller, a phase modulator, a fourth polarization controller, an opto-isolator, a 3dB optical coupler, a Sagnac loop filter, single mode dispersion fiber, an optical amplifier and a photoelectric detector. By making use of the nonlinear dynamic behavior of light when the light enters the semiconductor laser system, by exciting the single-cycle oscillation effect P1 of the semiconductor lasers to generate similar beam-shaped spectra with variable frequency space, and by adjusting the intensity of injecting the master laser to the slave laser or the off-resonance frequency between the two lasers, the invention realizes the tunable microwave photonic filter with a tunable filtering window and at the same time the reconfigurability and multi-tap structure of the filters are realized.

We have demonstrated a novel Sagnac loop and micro-ring based laser cavity which is simple and reliable, with accurately controlled reflectivity and negligible excess loss. The resonant wavelength of a 2 μm radius micro-ring is shown to be lithographically controlled to a standard deviation of 3.6 nm. Both C- and O-Band lasers based on Sagnac loop mirror and micro-ring cavity have been demonstrated. The lasers are shown to be able to be modulated at 40 Gb / s.

The invention relates to a method and a device for demodulating a frequency domain fiber grating sensing network. In the invention, an electro-optic modulator is connected with a Sagnac loop; an FBG sensing network formed by connecting a plurality of sensing FBGs in series is connected with the Sagnac loop by a three-port 3-dB fiber coupler; the bragg wavelengths of each reference FBG on a reference FBG array are the same as the sensing FBGs with same sequence numbers. The electro-optic modulator is driven by a RF signal with variable frequencies. When the frequencies of the RF signal are changed, the change of the transmittance is detected by a photodiode; the drift amount of the bragg wavelengths of each sensing FBG on the sensing network is obtained by carrying out fast Fourier transformation and relevant operations on the output data of the photodiode collected by a collecting card, and finally the change of the sensed physical quantity is obtained. The invention can have an extremely high response speed for meeting the requirements of real time sensing; besides, as the sensing network is connected with the Sagnac loop, the performances of anti-external temperature fluctuation and anti-mechanical disturbance of the device are high.

In various exemplary embodiments, the present invention provides coherent non-differential detection systems and methods for the detection of optical communication signals by the Brillouin fiber amplification of an optical communication signal carrier, the coherent non-differential detection systems including: a Sagnac loop including a single-mode fiber span; a fiber span with negligible birefringence (i.e. a spun fiber span or the like); or a fiber loop with negligible birefringence (i.e. a spun fiber loop or the like).

The invention relates to an oscilloscope detection temperature sensor based on parallel connection of a Sagnac loop and an FP cavity, which comprises a first coupler, an isolator, a second coupler, anFP cavity, an attenuator, a third coupler a Sagnac loop, a fourth coupler and a flat top grating, and is characterized in that the first coupler is connected with the isolator and a first inlet of the second coupler, one part of a first outlet of the second coupler is connected with an inlet of the FP cavity, the other part of the first outlet of the second coupler is connected with the Sagnac loop through the attenuator and the third coupler, one part of a second inlet of the second coupler is connected with an outlet of the FP cavity, the other part of the second inlet of the second coupleris connected with the attenuator, a second outlet of the second coupler is connected with a first inlet of the fourth coupler, a first inlet of the fourth coupler is connected with an inlet of the flat top grating, an outlet of the flat top grating is connected with a second inlet of the fourth coupler, a second outlet of the fourth coupler is connected with a photoelectric detector and an oscilloscope. The sensitivity of the temperature sensor based on the parallel connection of the Sagnac loop and the FP cavity is improved by dozens of times than that of a temperature sensor based on a single Sagnac loop structure by using a vernier effect.

An optical device which monolithically integrates a variety of structures to route or demultiplex data. One or more ring resonators are used to couple a control signal into and out of a waveguide loop residing within the optical device. The device includes a waveguide loop interferometer, such as a Sagnac loop, and a nonlinear element, such as a semiconductor optical amplifier, inserted in the loop. A ring resonator removes the control signal from the waveguide loop after it passes through the nonlinear element. The control signal is removed via a path that is independent of paths used for managing the flow of data through the optical device. Data is selectively outputted from one of two output ports, depending upon the state of the nonlinear device, as determined by the control signal.

The invention relates to an optical fiber Prague raster sensing network fast demodulating method and a device thereof. The invention uses a narrow linewidth continuous semiconductor laser as an optical source; acousto-optic modulators are asymmetrically arranged inside a Sagnac ring; a FBG sensing network is connected with the Sagnac ring through a three-port 3-dB optical fiber coupler; each FBG in series at the sensing network has the consistent Prague wavelength with the central wavelength of a laser optical source under a room temperature; the acousto-optic modulator is driven by the radio-frequency signal with changeable frequency. When the frequency of the radio-frequency signal is changed, the transmissivity of a Sagnac interferometer is changed. The drift rate of the Prague wavelength of each sensing FBG at the sensing network is obtained by fast Fourier transform and related operations, and the sensed physical quantity variation is obtained finally. The method is a novel FBG sensing network which is suitable for the field which requires the sensing network with multiple nodes, high precision, good electromagnetic interference resistance and real time monitoring.

The invention discloses a method and device for fabrication of a frequency degenerate multi-photon entangled source using an integrated waveguide. The method comprises the following steps that (1), two pulsed light beams with different frequencies are obtained; (2), intensity of the two pulsed light beams is amplified; (3), relative time delay of the two pulsed light beams is adjusted to synchronize the two pulsed light beams, and the polarization directions of the two pulsed light beams are adjusted to be consistent; and (4), the two pulsed light beams are introduced into a Sagnac loop, eachpulsed light beam is divided into two beams of light orbiting in different directions and generates photon pairs under the spontaneous four-wave mixing of a third-order nonlinear medium, the pulsed light beams returning from different directions are combined and elicited from the Sagnac loop, and the frequency degenerate multi-photon entangled source is obtained. The method has higher stability and expansibility, can achieve complexity which is difficult to achieve in space optics, and has a high application prospect.

The invention relates to a fiber grating sensing demodulation method and devices based on microwave photon filters. The method converts the wavelength drift quantity of sensing Fiber Bragg Grating into the strength variable quantity of electric signals with specific frequency by utilizing chirped fiber grating unequal-armed Sagnac circular structure and utilizing the filter action of the structure to the electric signals, thus demodulating the wavelength information. The devices for realizing the method comprise a broadband light source, a three-port optical circulator, a sending Fiber Bragg Grating, an electro-optical modulator, an optical fiber amplifier, a Sagnac ring, a photodetector and an electro-dynamometer; two ports of a 3-dB four-port optical fiber coupler are optically connected with the two ends of a linear chirped fiber grating by two-section optical fiber , and the other two ports thereof as used as the input port and the output port of the Sagnac ring. The invention changes the wavelength variable quantity of the fiber grating into the power variable quantity of modulation electric signals, thus implementing power detection to the demodulated electric signals and greatly reducing the cost and complexity of the demodulation system.

An optical filtering device based on a silicon-based double-Sagnac-loop-mirror loop structure comprises two Sagnac loop mirrors and a directional coupler, wherein waveguides on one side of the two Sagnac loop mirrors are connected, waveguides on the other side are respectively connected with two waveguides on one side of the directional coupler, and an input port, a transmission port and a reflection port are arranged at the other side of the directional coupler. According to the invention, the coupling coefficient of each coupler and the length of each waveguide are adjusted, and the transmission function and the reflection function of the double-Sagnac-loop-mirror loop structure can be changed, so that an interleaver adjustable in wavelength and a comb filter adjustable both in wavelength and bandwidth are realized; in addition, the size is small, the adjusting efficiency is high, and the extinction ratio is high.

The related loop fiber laser multiple wavelength output device based on mixed gain of Lamb amplifier and erbium-doped fiber amplifier comprises: an optical loop with second port connected with Sagnac loop filter included two polarization controllers whose another end connects with 3dB optical coupler port, an optical coupler, a fiber Lamb amplifier, and the erbium-doped fiber amplifier. This invention can output laser stably.

The invention relates to a dual-Sagnac loop chromatic dispersion measuring device and method. The dual-Sagnac loop chromatic dispersion measuring device comprises a broadband light source module, a frequency spectrum monitoring module, a control and data processing module and a dual-Sagnac loop chromatic dispersion detection module. The dual-Sagnac loop chromatic dispersion detection module comprises a first Sagnac loop and an anti-interference module. The first Sagnac loop comprises a first single mode fiber, a second single mode fiber, a frequency shift controller, a polarization controller and a first optical fiber coupler. The anti-interference module comprises a third single mode fiber, a fourth single mode fiber, a disturbance source and a second optical fiber coupler. The dual-Sagnac loop chromatic dispersion measuring device and method have the advantages that the anti-interference module is additionally arranged in an existing chromatic dispersion detection module, the disturbance source is actively introduced so as to restrain the influence of an external interference signal, the contrast ratio of interference fringes is improved, so that the chromatic dispersion measuring precision is improved, the structure is simple, and the measuring speed is high.

The invention relates to an optical gyroscope, in particular to a fiber laser gyroscope. It consists of an ultra-narrow linewidth fiber mode-locked laser, a wavelength division multiplexer, a fiber Sagnac loop, a circulator, a polarizer and a detector, and a difference frequency signal processing circuit. It is characterized in that it uses a semiconductor pump with a pigtail Active fiber ring laser with Sagnac effect composed of laser, isolator, wavelength division multiplexer and gain fiber; two sets of fiber coupler, circulator, ultra-narrow linewidth photon injection fiber mode-locking device, polarizer and detector The mode selection filter output system composed of the device forms the optical path scheme of the fiber laser gyroscope. The photon injection fiber mode-locking technology introduced in the present invention can make the gyroscope work stably in the ultra-narrow linewidth single longitudinal mode laser state, thereby obtaining the high-resolution detection result of the angular rate; The difference can automatically eliminate the zone-locking effect of the laser gyro. As a high-precision gyroscope, the invention can be applied to inertial measurement units of aviation, spaceflight, navigation and land weapons.

The invention relates to a method and a device for fast measuring the length of an optical fiber. In the invention, an ordinary continuous semiconductor laser is used as an optical source; an electro-optic modulator and the optical fiber to be measured are all connected with a Sagnac loop; wherein, the electro-optic modulator is asymmetrically arranged in the Sagnac loop and near one opening of an optical fiber coupler; the electro-optic modulator is driven by a RF signal the frequency of which can be linearly scanned; when the RF signal frequency is changed, the transmittivity of a Sagnac interferometer is changed; the variable frequency of the transmittivity is relevant with the length of the optical fiber to be measured; the change of the transmittivity is measured by a photodiode; the output end of the photodiode is connected with a data collection card; The length of the optical fiber to be measured is obtained by fast Fourier change and relevant operations on the the data collected by the data collection card. The method and the device for fast measuring the length of the optical fiber overcome the defects of being incapable of simultaneously meeting the demand of measuring with large range and high precision and having a relative lower cost. As the optical fiber to be measured is connected with the Sagnac loop, the anti-external temperature fluctuation and the mechanical anti-disturbance performances of the device are high.

The invention relates to a method and a device for demodulating a fiber bragg grating sensor array. In the invention, a continuous semiconductor laser with narrow line width is used as an optical source; an electro-optic modulator is connected with a Sagnac loop; an FBG sensing array is connected with the Sagnac loop by a three-port 3-dB fiber coupler; the bragg wavelengths of each sensing FBG connected in series on the sensing array under the room temperature are consistent with the central wavelength of the laser optical source; besides, the reflection rates are all less than 3 percent; the electro-optic modulator is driven by a RF signal the frequencies of which can be modulated; the change of the transmittance is detected by a low-speed photodiode; the drift amount of the bragg wavelengths of each sensing FBG on the sensing array is obtained by carrying out fast Fourier transformation and relevant operations on the data collected by a collecting card, and finally the change of the sensed physical quantity is obtained. The invention can have an extremely high response speed for meeting the requirements of real time sensing and has a relative lower cost; besides, as the sensing array is connected with the Sagnac loop, the performances of anti-external temperature fluctuation and anti-mechanical disturbance of the device are high.

The invention relates to a fiber bragg grating wavelength demodulation system with a long-period fiber bragg grating Sagnac loop, belonging to the optical fiber sensor field. In the system, the light source of the demodulation system is a line cavity type fiber laser formed by using a fiber Bragg grating (4) and the Sagnac loop (8) with a long-period fiber bragg grating as the endoscopy; one end of the long-period fiber bragg grating (7) is connected with the third port (63) of a 2*2 coupler, the other end of the long-period fiber bragg grating is connected with the fourth port (64) of the 2*2 coupler, thus forming the Sagnac loop with the long-period fiber bragg grating; one end of the fiber Bragg grating is connected with the first port (61) of the 2*2 coupler through an Er-doped fiber (5), the other end is connected with the third port (63) of a wavelength division multiplexer; the second port (32) of the wavelength division multiplexer is connected with a pump light source (2), and the first port (31) of the wavelength division multiplexer is connected with a signal processing system (1). By using the demodulation system of the invention, the defects that signal-to-noise ratio and measurement precision are low and the system is subject to environmental disturbance.

The present invention relates to an oscilloscope detection temperature sensor based on serial connection of a Sagnac loop and an FP cavity. The sensor comprises a first coupler, an isolator, a secondcoupler, a Sagnac loop, a circulator, a FP cavity, a third coupler, a flat grating and an attenuator. The first coupler is connected with the isolator, the second coupler and an inlet of the Sagnac loop, an outlet of the Sagnac loop is connected with a second inlet of the second coupler, a second outlet of the second coupler is connected with a first inlet of the circulator and the inlet of the FPcavity, the outlet of the FP cavity is connected with a second inlet of the circulator, a second outlet of the circulator is connected with the third coupler, the flat grating and the attenuator, andthe attenuator is connected with a photoelectric detector and the attenuator. The oscilloscope detection temperature sensor based on the serial connection of the Sagnac loop and the FP cavity employsa vernier effect is several-dozen times higher in sensitivity than a temperature sensor based on a single Sagnac loop structure.

The invention discloses a high-precision rapid measurement device and method for an engine blade tip gap, and belongs to the field of engine blade tip gap measurement. The high-precision rapid measurement device for an engine tip gag comprises a mode-locked pulse laser, a wavelength division demultiplexer, a loop unit, an isolator, a delay line, an aero-engine, a measuring head, a signal acquisition and processing apparatus, a balance detector, a wavelength division demultiplexer,a signal locking apparatus, a coupler and an electro-optical modulator. The invention further discloses a high-precision rapid measurement device and method for the engine blade tip gap. The measurement resolution is remarkably improved by combining the ultrashort mode-locked pulse laser and a Sagnac ring, the measurement value of the blade tip gap of each turbine blade can be obtained in the high-rotating-speed working state of the aero-engine, the highest measurement precision can reach the sub-nanometer magnitude, and a subsequent signal processing method is simple and efficient.

A modified Sagnac loop phase-modulated microwave photonic link with a pulsed optical source is disclosed. Unlike a conventional Sagnac loop, the optical phase offset of the loop can be adjusted to quadrature by applying a synchronized modulation signal to an in-loop phase shifting phase modulator. Thereby, it exemplifies the fundamental RF response.

A Sagnac loop coherent phase modulated RF photonic link employing an ACP-OPLL linear phase demodulator was presented. This structure demonstrated stable signal transmission over a 1-km long coherent RF photonic link.

In various exemplary embodiments, the present invention provides coherent non-differential detection systems and methods for the detection of optical communication signals by the Brillouin fiber amplification of an optical communication signal carrier, the coherent non-differential detection systems including: a Sagnac loop including a single-mode fiber span; a fiber span with negligible birefringence (i.e. a spun fiber span or the like); or a fiber loop with negligible birefringence (i.e. a spun fiber loop or the like).

The invention belongs to the field of optical fiber sensing and signal processing technologies and particularly provides a system for detecting the position of a sound source by using optical fibers. The system comprises a broad spectrum light source, an optical fiber interference system, a sensing optical fiber, a photoelectric detector, a data acquisition card and a signal processing platform. The sensing optical fiber forms a fiber-optic acoustic sensor array by using a full optical fiber sensing probe, and realizes the simultaneous collection of multi-path optical signals through the wavelength division multiplexing process. The light emitted from the light source is input into the optical fiber interference system. A signal applied onto the sensing optical fiber is interfered by the interference system and then is collected by a computer after being detected by the photoelectric detector. The signal processing platform processes the received acoustic signal to obtain the position information of the sound source, and then displays the position coordinates of the sound source. The fiber-optic acoustic sensor array is composed of a Sagnac loop-based interference light path, or a feedback-based interference light path. According to the technical scheme of the invention, the system can determine the position of the sound source, and has the advantages of wide detectable sound frequency band, anti-electromagnetic interference, corrosion resistance and the like. The system can be used for detecting low-altitude flying objects, underwater submarines and the like.

An adjustable interleaver based on silicon-substrate Michelson GT interferometer including a first directional coupler, a first resonance cavity unit and a second resonance cavity unit, wherein the length of each of the first resonance cavity unit and the second resonance cavity unit is equal to that of a resonance cavity in cascade connection with one side of the first directional coupler. A first port of the first directional coupler is provided with a first wave guide directly connected with the input terminal of the first resonance cavity unit. A second port of the first directional coupler is provided with a first phase shifter connected with the input terminal of the second resonance cavity. The first resonance cavity unit includes a first Sagnac loop mirror, a second phase shifter and a third Sagnac loop mirror connected in series. The second resonance cavity unit includes a second Sagnac loop mirror, a second phase shifter and a third Sagnac loop mirror connected in series. The ratio between the length difference Delta L of two arms of the first directional coupler and the length d of the resonance cavities is constant and can be in proportional control. According to the invention, adjustment of the central wavelength of a square filter wave spectrum of the interleaver is realized through the Sagnac loop mirrors. The device is small in integral size and high in adjustment efficiency.

A microwave photonic filter based on a photonic crystal fiber sagnac loop comprises a broadband light source, a sagnac loop, a coupler B, a spectrum analyzer, a phase modulator, an analog signal generator, a single mode fiber, a photoelectric detector and a spectrum analyzer. The sagnac loop is composed of an sdB coupler A, a polarization controller and a liquid-filled photonic crystal fiber; the photonic crystal fiber of the sagnac loop is filled with liquid, the birefringence is changed by changing the temperature, the wavelength interval of the sagnac loop transmission spectrum is affected, the wavelength interval of input light is changed accordingly, and the filter passband center frequency can be tuned continuously. The microwave photonic filter has the advantages that the microwave photonic filter is simple in structure and easy to implement, the photonic crystal fiber of the sagnac loop is filled with liquid, the temperature is changed, the continuous tuning of the filter passband center frequency can be implemented, the dynamic response range is large, the manufacture technology is mature, cost is low, and the promotion and application are benefited.