38 results about "Laser phase noise" patented technology

The invention relates to a self-adaptive damage compensation method and system for a digital-related optical communication system. The self-adaptive damage compensation method includes inserting two pulse modulation pilot frequency signals symmetrically distributed on an input signal frequency fc (fiber channel) at a transmitting terminal; acquiring an input signal power spectrum by the Fourier transform at a receiving terminal, and receiving the pilot frequency signals of a signal power spectrum and subjecting the pilot frequency signals to location and filtering extraction; calculating size of frequency offset of a vibration laser and performing compensation by a pilot frequency; acquiring pilot time domain waveforms by the Fourier transform and calculating a delay delta tau between two pilot light pulses, and calculating size of dispersion by the delta tau and performing the compensation; finally extracting pilot phase noises and subtracting the same from a signal phase so as to eliminate laser phase noises and nonlinear fiber damages. The self-adaptive damage compensation method has the advantages of high accuracy, low complexity, small occupation of bandwidth and fast response speed, so that self-adaptive compensation of various damages can be realized.

A high resolution measurement method and apparatus for tracking wavelength transients in tunable lasers. The apparatus comprises a Mach-Zehnder interferometer (MZI) which is used to generate a self-heterodyne signal between the wavelength transient to be measured, which is effectively the laser signal passed along the time-delayed arm of the MZI, and the laser wavelength after the tuning transient has subsided, which is effectively the same laser signal passed along the direct arm of the MZI. The heterodyne signal is detected on a receiver, and can then be measured with the frequency resolution typical of electronic measurements, such as by means of an oscilloscope. The only laser required is the laser under inspection. The wavelength measurement accuracy is up to twice the laser linewidth, and is only effectively limited by the laser phase noise. The method can be used to implement an automatic frequency control system for tunable lasers.

The invention discloses a method and device for monitoring and controlling a high-precision optical fiber optical frequency comb. The method and device are used for monitoring and controlling working conditions of links of the optical fiber optical frequency comb and improving the long-term stability, the operation reliability and the product replicability of the optical fiber optical frequency comb. By means of the device, pulse carrier-envelope phases output by an optical fiber laser oscillator and optical fiber amplifiers in all stages are monitored, transmission and fluctuation of laser phase noise in the power amplification process are observed and controlled, carrier-envelope phase output signals of the main amplifier are negatively fed back to a carrier-envelope phase control unit in the laser oscillator, namely an electronic control polarization controller modulates the pulse polarization evolution process or modulates the pump light strength of the laser oscillator, and stable control over the carrier-envelope phases is achieved. By means of the method and device, the working conditions of the laser oscillator and the amplifiers in all stages can be monitored and controlled in real time, monitoring indexes are timely and comprehensive, and a stable and reliable feedback mechanism is provided.

This application describes methods and apparatus for distributed fiber optic sensing that reduce or compensate for the effects of laser phase noise. The method involves repeatedly interrogating an optical fiber (101), where each interrogation involves launching at least one interrogating pulse into the optical fiber; detecting optical radiation which is backscattered from within the fiber, and forming a measurement signal from a plurality of sensing portions of the fiber. The method involves forming a laser noise template based on the measurement signals within a frequency band of interest from a first set of said sensing portions; and applying a correction to the measurement signals from said plurality of sensing portions based on said laser noise template. The first set of sensing portions may be temperature and/or strain stable portion from an isolated section of fiber (301, 303) or may comprise a selected set of sensing portions, which may include substantially all the sensing portions, which are averaged to form the laser phase noise template. For a phase based DAS type sensor the laser phase noise template may simply be subtracted from the measurement signals. For an intensity based sensor it may be necessary to polarity align and normalize the signals of the first set before averaging and then determine a gain-time profile for each sensing portion prior to applying the correction.

The invention provides a laser phase noise-based miniature random number generator. The random number generator comprises a laser device, a coupler, a photoelectric detector, an analog-digital converter and a post-processing module, wherein the laser device generates continuous light or pulse light; the continuous light or the pulse light generates interference at the coupler, and phase noises are converted into an intensity signal; the coupler is connected with the photoelectric detector, and the intensity signal is subjected to photoelectric conversion through the photoelectric detector; the photoelectric detector is connected with the analog-digital converter, and the analog-digital converter performs quantification on an output electric signal of the photoelectric detector to obtain an initial random bit; and the post-processing module performs randomness optimization on the initial random bit to obtain a final random bit. Compared with the prior art, the random number generator has the advantages that an output result is stable, random number generation does not depend on polarization and phase compensation technologies, and the random number generation speed is high.

The invention provides a laser phase noise elimination device, system and method. The device comprises a Mach-Zehnder interferometer and a fiber delay loop. The fiber delay loop is coupled on the reference arm of the Mach-Zehnder interferometer through a first optical coupler. The fiber delay loop comprises a series connected acousto-optic modulator and a delay fiber of the preset length, wherein the preset length is not greater than the coherent length of the laser. With application of the laser phase noise elimination device, system and method, the problem that the optical frequency domain reflectometer technology has low spatial resolution for long distance measurement in the relevant technology can be solved so that the spatial resolution of the optical frequency domain reflectometer technology for long distance measurement can be enhanced.

A system for gravity measurement includes one or more atom sources, two or more laser beams, and a polarizing beamsplitter and a retro-reflection prism assembly. The one or more atom sources is to provide three ensembles of atoms. The two or more laser beams is to cool or interrogate the three ensembles of atoms. The polarizing beamsplitter and the retro-reflection prism assembly are in a racetrack configuration. The racetrack configuration routes the two or more laser beams in opposing directions around a loop topology, intersecting the three ensembles of atoms with appropriate polarizations chosen for cooling or interferometer interrogation. The three ensembles of atoms are positioned coaxially when interrogated.

The present invention relates to a method and device for reducing the phase noise of a laser signal from a laser source. This device comprises a first current generator for supplying a driving current to the laser source in view of producing the laser signal. A phase noise detector is responsive to the laser wavelength for generating a phase error signal and a second current generator is responsive to the phase error signal for generating a compensation current added to the driving current supplied to the laser source for generating a phase-adjusted laser signal. The device therefore defines a phase stabilization loop formed by the phase noise detector and the second current generator, for reducing the phase noise of the laser signal.

Embodiments of the present disclosure provide a signal processing apparatus, a signal transmitting apparatus and a receiver, which are adapted for a frequency division multiplexing system having a high-order modulation format. A receiver having a high-magnification sampling rate by inserting a pilot signal between neighboring subcarriers at a transmitter side, calculating a laser phase noise according to a phase of the pilot signal at a receiver side, and performing down-sampling and equalization processing after performing carrier phase recovery according to the laser phase noise, so that a laser phase noise having a wide frequency may be accurately compensated, thereby having a relatively powerful carrier phase recovery ability.

The invention discloses a light IQ modulator parameter monitoring method and device and relates to the field of a light IQ modulator. The method comprises the steps of collecting plural signals outputthrough modulation of the light IQ modulator; converting the collected plural signals into a track constellation diagram; and inputting the signal track constellation diagram into a trained deep convolutional neural network, reading a mapping relationship between transmitting end time differences and amplitude ratios, and adjusting light IQ modulator parameters according to the mapping relationship, wherein the mapping relationship is output by the deep convolutional neural network. According to the light IQ modulator parameter monitoring method and device provided by the invention, a zero difference detection mode is employed, a signal light path and a light source path are guaranteed to be equal in length, and further influence resulting from laser phase noises is eliminated, and inconvenience that two lasers are employed in an existing method and the influence resulting from the phase noises needs to be eliminated in a digital signal processing mode is avoided.

A laser amplifier phase noise measurement system which comprises a master oscillator, an optical beam splitter, a phase modulator, a phase modulation signal generator, an optical path adjustment device, an optical path adjustment device controller, a laser amplifier to be measured, laser alignment systems, a high reflectivity mirror, a power receiver, a total reflective mirror, polarization rotators, a polarization beam combiner, polarizers, photoelectric detectors, phase demodulation systems, 3dB electricity beam splitters, pi/2 phase shifters and a data acquisition module. The phase modulator is connected with the phase modulation signal generator which is used for applying modulating signals with needed frequencies on the phase modulator, and the optical path adjustment device is connected with the optical path adjustment device controller which accurately controls the optical path adjustment device. According to the laser amplifier phase noise measurement system, the influence of factors such as the polarization state and the amplitude ratio of a light beam on the phase noise measurement system can be avoided, and the accurate measurement of laser phase noise can be achieved.

The invention provides an optical fiber vibration measurement device and method for improving light source noise, and relates to the field of optical fiber distributed vibration measurement. In a feed-forward loop of a light source noise suppression feed-forward structure, two paths of mutually orthogonal interference optical signals are obtained based on an optical fiber interferometer and a 90-degree optical mixer, are respectively output to a photoelectric balance detector 1 and a photoelectric balance detector 2 and are converted into two paths of interference electric signals which are output to a tracker. A light source noise suppression feed-forward structure is used for phase noise suppression of continuous light output by a laser, the light source noise suppression feed-forward structure is added to a classical 0-OTDR measuring device, laser phase noise is reduced, and the measurement precision of external vibration signals is further improved.

The embodiment of the invention provides a subcarrier modulation format identification method and device in an OFDM-EON system. The method comprises the following steps: calculating signal MMS valuesof subcarriers in X polarization and Y polarization of an OFDM-EON system, and calculating an MMS average value corresponding to the subcarriers with the same number in the X polarization and the Y polarization; sorting the various preset modulation formats according to the MMS values of the various preset modulation formats, and taking the average value of the MMS values of any two adjacent preset modulation formats after sorting as a judgment threshold value; and comparing the average value corresponding to each number with each decision threshold, and determining the modulation format of the subcarrier of each number according to a comparison result. According to the embodiment of the invention, the dynamically changing subcarrier modulation format in the OFDM-EON system can be intelligently, rapidly and stably identified, and the method has high tolerance to polarization mode dispersion, laser phase noise and frequency offset.

The invention discloses a multi-wavelength laser phase noise elimination and frequency stabilization device and method. The invention discloses a device for simultaneously realizing high-frequency phase noise suppression of two lasers with different wavelengths and ensuring long-term stability of frequency of the two lasers with different wavelengths. A cavity length stabilizing system stabilizes a tunable Fabry-Perot cavity to a main laser; a first laser frequency stabilizing system locks a first laser to the tunable Fabry-Perot cavity, a second laser frequency stabilizing system locks a second laser to the tunable Fabry-Perot cavity; and first Fabry-Perot cavity transmission light and second Fabry-Perot cavity transmission light are input into an injection locking system so as to be subjected to power amplification. The invention also discloses a method for simultaneously realizing high-frequency phase noise suppression of two lasers with different wavelengths and ensuring long-term stability of the frequency of the two lasers with different wavelengths. By locking the Fabry-Perot cavity to the main laser with extremely small frequency drift, the cavity length change of the Fabry-Perot cavity caused by external environment temperature change and cavity absorption is reduced, and the effect of long-term stability of laser frequency is achieved.

The invention relates to a wide-range frequency sweeping technology for narrow-linewidth laser. A closed-loop feedback optical phase-locked laser frequency sweeping method is adopted. According to theclosed-loop feedback light phase-locked laser frequency sweeping method, a frequency sweeping light signal emitted by a DFB-LD passes through an unbalanced Mach-Zehnder optical fiber interferometer to obtain an intermediate frequency beat signal; the intermediate frequency beat signal is compared with the low-phase-noise reference signal with the same frequency to obtain an error signal of laserfrequency sweeping nonlinear and phase noise for feedback control of laser driving current. The closed-loop feedback optical phase-locked laser sweep frequency corrects laser sweep frequency and phasenoise through a closed loop to achieve phase locking of beat frequency signals and reference signals, and thus linear sweep frequency optical signals with the phase noise effectively restrained are obtained. According to the wide-range frequency sweeping technology for the narrow-linewidth laser, the closed-loop feedback light phase-locked laser frequency sweeping method is provided, wide-range frequency sweeping of the narrow-linewidth laser is achieved, frequency sweeping nonlinearity is effectively corrected, the laser linewidth is compressed, laser phase noise is reduced, and the measuring distance, the resolution and the sensitivity of equipment are improved.

The invention relates to the technical field of laser testing, in particular to a laser phase noise measuring method and system. The system comprises a laser, a delay interference device and a spectrum analyzer, and further comprises a balanced photoelectric detector, the laser is used for generating a laser signal and transmitting the laser signal to the delay interference device, the delay interference device is used for obtaining two paths of phase noise optical signals through interference after receiving the laser signal, and the spectrum analyzer is used for analyzing the phase noise optical signals. The delay interference device transmits the obtained two paths of phase noise optical signals to the balance photoelectric detector, the balance photoelectric detector generates radio frequency signals according to the received two paths of phase noise optical signals and transmits the radio frequency signals to the spectrum analyzer, and the spectrum analyzer displays a measurement result according to the received radio frequency signals. According to the invention, the amplitude of the radio frequency signal output to the spectrum analyzer is very strong, the noise signal of the laser can be clearly observed on the spectrum analyzer, and a more accurate noise measurement result can be obtained.