40results about How to "Suppress phase noise" patented technology

The invention relates to an all-optical phase noise inhibition method for coherent detection. Aiming at the current situation that the local oscillation coherent reception phase noise characteristic is improved through an ultra-low noise performance light source and complex circuit processing technology at present, the all-optical method is provided to inhibit the phase noise and improve the receiving performance. The method comprises the steps that: through a transmitting terminal, one path of a pair of light carrier waves with relevant properties is loaded with information to form signal light, while the other path is used as coherent light and is subjected to wave combination with the signal light to enter optical fibers for transmission; and a receiving terminal performs frequency mixing on the extracted signal light and coherent light, and photovoltaic conversion and signal demodulation are performed in turn. In the method, the phase noise in the coherent detection is inhibited by utilizing the characteristic that homologous generated light carrier waves have relativity without using a local light source and a complex signal processing process, so the structure is simplified and the cost is reduced. In addition, multiple groups of light carrier waves can be acquired by using the technology of combining a wide-spectrum and multi-wavelength light source with spectral partitioning, so the inhibition of the phase noise in a multi-channel coherent light communication system is easy to realize.

The invention discloses a phase-locked loop system, which comprises an input end, an output end, a first phase frequency detector, a first charge pump connected with the first phase frequency detector, a first low-pass filter connected with the first charge pump, a first voltage-controlled oscillator connected with the first charge pump and the first low-pass filter, a second phase frequency detector connected with the first voltage-controlled oscillator, a second charge pump connected with the second phase frequency detector, a second low-pass filter connected with the second charge pump, a second voltage-controlled oscillator connected with the second charge pump and the second low-pass filter, a first digital frequency divider connected between the first phase frequency detector and the second voltage-controlled oscillator, and a second digital frequency divider connected between the second phase frequency detector and the second voltage-controlled oscillator. The invention also discloses a working method of the phase-locked loop system. Input noise and the phase noise of the second voltage-controlled oscillator can be simultaneously suppressed, so that the noise of the phase-locked loop system is greatly reduced.

A phase-shifting fiber Bragg grating strain sensing system based on a photoelectric oscillator comprises a wave-length tunable laser; an input end of a polarization controller is connected with an output end of the wave-length tunable laser; a light input end of a phase modulator is connected with an output end of the polarization controller; an end a of an optical circulator is connected with an output end of the phase modulator; one end of a phase fiber Bragg grating pi is connected with an end b of the optical circulator; an input end of a photoelectric detector is connected with an end c of the optical circulator; an input end of a microwave power beam splitter is connected with an output end of the photoelectric detector; an input end of a microwave power amplifier is connected with a first output end of the microwave power beam splitter; an output end of the microwave power amplifier is connected with a radio frequency input end of the phase modulator; an input end of a frequency spectrograph is connected with a second output end of the microwave power beam splitter.

The invention discloses a phase unwrapping algorithm based on MECKF. According to the algorithm, an embedded cubature Kalman filter modified via a Levenberg-Marquardt method, a local phase gradient estimation algorithm based on a corrected matrix beam model (AMPM) and a quantified tracking strategy are combined to unwrap a wound phase image accurately in high efficiency. The algorithm comprises the main steps that a recursion state estimation model of the phase unwrapping algorithm based on MECKF is established, and the phase gradient estimation method based on the AMPM is used to obtain phase gradient information needed by the recursion state estimation model; and the quantified path guiding graph strategy, the recursion state estimation model of the phase unwrapping algorithm based on MECKF is guided to unwrap wound pixels rapidly along a path from a high-quality area to a low-quality area till phases of all wound pixels are unwrapped. The algorithm is characterized by higher precision and robustness.

The invention belongs to the field of signal sources, and specifically discloses a fractional frequency division circuit for stray suppression. The fractional frequency division circuit includes a phase detector, a loop filter, and a voltage-controlled oscillator connected in sequence; in addition, the fractional frequency division circuit also includes a frequency divider, a synchronization module, and a Σ-Δ modulator; wherein, the voltage-controlled oscillation The output signal of the detector, one way is directly output, and the other way is fed back to the frequency divider; the reference clock signal is divided into two ways, one way is divided by two and enters the phase detector as the phase detector reference clock signal, and the other way is used as the clock signal of the synchronization module , used to beat the frequency division ratio generated by the Σ-Δ modulator into the frequency divider; one way of the frequency-divided clock signal generated by the frequency divider enters the phase detector, and the other enters the Σ-Δ modulator and is used as a Σ-Δ modulation device clock signal. Compared with the fractional frequency division circuit in the prior art, the present invention adds a frequency divider and a synchronization module, and at the same time adds a random jitter module inside the FPGA to suppress the limit cycle phenomenon, further reducing spurs.

The invention discloses an OCT (optical coherence tomography)-based high-sensitivity measurement system and method with a large dynamic range of flow speed. According to the measurement system and method disclosed by the invention, a two-dimensional scanning strategy combining fast scanning driven by saw-tooth waves and slow-speed scanning driven by step waves is adopted, and a high-speed CMOS (complementary metal oxide semiconductor) camera is utilized for acquiring an interference spectrum. A traditional phase resolution algorithm is adopted in the fast scanning direction for extracting high-flow-speed information, and a high-order correlation phase resolution algorithm is adopted in the slow-speed scanning direction for extracting slow-flow-speed information and a phase variance value corresponding to the large dynamic rate of the flow speed. A flow speed image is synthesized from the high-flow-speed information and the slow-flow-speed information. After space filtering and binarization are performed on a phase variance image, a mask image is obtained, and the flow speed image is processed by the mask image to get the final flow speed image. According to the measurement system and method disclosed by the invention, the dynamic range of measurement flow speed can be expanded, and the noise-limited speed detection sensitivity is further broken through.

The invention provides a fiber laser frequency stabilization system using fast and slow locking, which includes an ultra-narrow linewidth fiber laser, an acousto-optic modulator, a phase modulator, a quadrature demodulation device and a feedback control device. It is characterized in that the laser output from the ultra-narrow linewidth fiber laser is modulated by an acousto-optic modulator and a phase modulator in sequence. After being input into a fiber grating Fabry-Perot interference cavity through a circulator, it is demodulated through a quadrature demodulation circuit. The slow PID controller is used to adjust the wavelength of the light source to compensate low frequency signals; the fast PID controller is used to adjust the acousto-optic modulator to compensate high frequency signals. This scheme can overcome the limitations of the frequency modulation response and frequency modulation bandwidth of the fiber laser, and realize the stable tracking between the output wavelength of the fiber laser and the reference resonant cavity.

The invention discloses a double-conjugation pumping modulating signal all-optical regeneration device based on an optical frequency comb. The all-optical regeneration device comprises a pumping laser device, the optical frequency comb, a photodecomposition multiplexer, a first coupler, erbium-doped optical fibers, a second coupler, a first section of HNLF, a wavelength selective switch, a second section of HNLF and a light bandpass filter. The device can be used for phase position regeneration of various degraded QPSL signals (including DQPSK) in a high-speed optical fiber communication network, so that influence on performance of an optical communication system by phase noise is reduced, the all-optical relay transmission distance is improved, and the error rate of a receiver is reduced. The invention further discloses a double-conjugation pumping modulating signal all-optical regeneration method based on the optical frequency comb. The double-conjugation pumping modulating signal all-optical regeneration device has the advantages of being concise in structure, stable in performance, easy to operate, remarkable in regeneration effect and the like.

The invention relates to a modulation circuit of a digital transmitter, a digital transmitter and a signal modulation method. The modulation circuit includes: a first synchronous circuit and a digital modulator; wherein, the first synchronous circuit includes a first synchronous unit and a second synchronous unit, which respectively phase-delay the first local oscillator signal or the second local oscillator signal Obtain the corresponding delay signal, and use the delay signal to adjust the phase of the digital baseband signal to generate the first adjustment signal and the second adjustment signal, so that the rising edge and falling edge of the first adjustment signal respectively fall on the first phase In the low-level interval of the oscillator signal; and the rising edge and falling edge of the second adjustment signal respectively fall in the low-level interval of the second local oscillator signal; the digital modulator uses the first local oscillator signal to perform the first adjustment signal modulating, generating a first radio frequency signal, and modulating the second adjustment signal with the second local oscillator signal to generate a second radio frequency signal.

The invention discloses a quadrature demodulation-based detection system and a quadrature demodulation-based detection method of a resonator optic gyro. Firstly, the phase of laser input to an opticalring resonant cavity is modulated, and synchronous quadrature demodulation is performed on clockwise and counterclockwise output signals going out of the cavity, wherein one quadrature demodulation signal is processed and then serves as an error signal for controlling the frequency of a laser through a servo loop, so that the output light frequency of the laser is locked at the resonant frequencythereof in a tracking manner; the other quadrature demodulation signal is processed and then output as a gyro signal. By the detection method of the resonator optic gyro, provided by the invention, automatic adjustment of the demodulation phase to the maximum sensitivity point is facilitated; the phase noise of a component in a system loop is suppressed, and the signal-to-noise ratio of the system is increased.

The invention relates to a correction method of phase noise at a multi-antennae Orthogonal Frequency Division Multiplexing (OFDM) system receiving end belonging to the wireless data-transmission field. The method places a pilot OFDM symbol every a plurality of data OFDM symbols. In the pilot symbols, the receiving end obtains a channel matrix of the current symbol as a reference channel matrix ofsubsequent data symbols according to a receiving signal on a pilot sub-carrier and the receiving end pilot. In the data symbols, the receiving end obtains the channel matrix of the current symbol according to the receiving signal on the pilot sub-carrier and a reservation signal at the receiving end and obtains a united matrix of a transceiving phase noise mean values by comparing the channel matrix with that of the pilot symbol. According to an estimate value of the transceiving phase noise mean values which are separated from the united matrix, a detection matrix is adjusted. The method cansimultaneous estimate and correct the phase noise of the transmitting and receiving antennas, and improve the system performance.

The invention relates to an optical fiber sensing technology and provides a method and device for phase noise suppression of a remote optical fiber interference system in spectral line operation. The device comprises a narrow linewidth single frequency laser, a first electro-optic phase modulator, an erbium-doped optical fiber amplifier, a transmission optical fiber, a second electro-optic phase modulator, an optical fiber Michelson interferometer, a photoelectric detector and a signal collecting and processing device. The method comprises the steps of applying modulating signals at the input end of the transmission optical fiber through the electro-optic phase modulators to generate multifrequency laser, utilizing the modulating signals of the electro-optic phase modulators again at the output end of the transmission optical fiber to recover the multifrequency laser generated by modulation to single frequency laser, simultaneously enabling phase difference between the two modulating signals to be odd number times of pi, and enabling the two modulating signals to have identical frequency and amplitude. The two electro-optic phase modulators are utilized to achieve recoverable spectral line operation, an SBS is suppressed, system phase noises are reduced, and accordingly maximum input power and the sensing distance of a sensing system are improved.