83 results about "Nonlinear phase shift" patented technology

System, apparatus and method of optical communication are provided for performing digital compensation of the self-phase modulation (SPM) effect experienced by a polarization-division multiplexed (PDM) orthogonal frequency-division multiplexed (OFDM) signal in fiber transmission by compensating a complex digital waveform representing one orthogonal polarization component of the optical PDM-OFDM signal based on both digital waveforms representing two orthogonal polarization components of the PDM-OFDM signal. The compensation of the digital waveform may be further based on an anticipated mean total nonlinear phase shift experienced by the signal during fiber transmission due to SPM. The compensation may be divided into pre-compensation at the PDM-OFDM transmitter and post-compensation at the PDM-OFDM receiver. The fiber transmission link preferably includes a pre-dispersion compensation module, distributed inline dispersion compensation modules, and a post-dispersion compensation module arranged in a judiciously chosen manner.

A method for overcoming the drawback in a fiber CPA laser system that includes a process of generating a large negative TOD by implementing an AODS in a pulse shaper as a dispersive component. The AODS is implemented to arbitrarily modulate both the spectrum shape and phase to control with controllable amplitude to generate different orders of dispersions including a large negative TOD for compensating the positive TOD generated by the pulse stretching and amplification processes. The AODS, implemented as a dispersive component, can be an active and controllable dispersive component to generate adjustable levels of dispersions for flexibly compensating any order of dispersions generated in the amplifier chain including the nonlinear phase shift. The AODS implemented as a dispersive component can be an active and programmable dispersive component to interactively generate adjustable levels of dispersions in response to output laser amplitude and pulse shape measurements for flexibly compensating any order of dispersions generated in the amplifier chain including the nonlinear phase shift to achieve the shortest pulse duration.

The invention provides a method and a device for optimizing dynamic transmission performance in a wavelength switched optical network. The method comprises the following steps of: making the optical signal-to-noise ratio cost of a dispersion-optimized optical path and the accumulative nonlinear phase shift have a one-to-one correspondence relationship by carrying out pre-dispersion compensation and post-dispersion compensation on source and destination nodes of an optical path; then, obtaining the optical signal-to-noise ratio cost of the optical path, using the power regulating quantity of a power-regulating point as a variable, by using the correspondence relationship, further setting a target function according to the optical signal-to-noise ratio cost and the optical signal-to-noise ratio of the optical path, and optimizing according to a predetermined optimization target and constraint conditions to obtain a node needing power regulation and the power regulating quantity of the same. According to the invention, the transmission performance of the optical path can be improved, and the blockage of physical layers, caused by the substandard physical transmission performance, is avoided.

The invention relates to an optical signal receiving method, an optical signal receiving device and an optical transmission system; the method comprises the following steps: receiving a 16QAM optical signal and local oscillator light, carrying out coherent detection to the signal and the light to obtain a 16QAM signal; according to the nonlinear phase shift factor and the drift phase error make-up corresponding to a previous 16QAM signal, pre-compensating for the phase of a current 16QAM signal, calculating the nonlinear phase shift factor and the shift phase error corresponding to the current 16QAM and takes the same as the nonlinear phase shift factor and the shift phase error required by compensating for a next 16QAM signal. The realization of the embodiment of the invention not only can effectively compensate for the shift phase error caused by frequency shift and phase shift between optical carrier and the local oscillator light, but also can compensate for the nonlinear phase shift of the 16QAM optical signal when transmitted in an optical fiber caused by nonlinear effect, thereby greatly reducing the error rate of the system and not producing format effect.

A nonlinearity compensation technique for a CO-OFDM transmission system in which a proportion (e.g. up to 50%) of OFDM subcarriers is transmitted along with a phase-conjugate copy (PCP) on another subcarrier (replacing a data carrying subcarrier) to enable nonlinear distortion compensation. Nonlinear distortion experienced by closely spaced subcarriers in an OFDM system is highly correlated. The PCPs are used at the receiver to estimate the nonlinear distortion (e.g. nonlinear phase shift) of their respective original subcarriers and other subcarriers close to the PCP. With this technique, the optical fibre nonlinearity due to the Kerr effect in OFDM systems can be effectively compensated without the complexity of DBP or 50% loss in capacity of the phase conjugate twin wave (PC-TW) technique. Moreover, the technique proposed herein can be effectively implemented in both single polarization and PMD systems, in both single channel and WDM systems.

The invention discloses an RF pilot based CO-OFDM system phase noise compensation method and system, and belongs to the technical field of optoelectronic communication. The system disclosed by the invention comprises a coarse compensation module and a fine compensation module, wherein a receiving end extracts the RF pilot by using a digital low-pass filter after coherent demodulation and analog-to-digital conversion; after being compared with a sending end and conjugated, the pilot is multiplied by a signal, so that coarse phase compensation is realized; the coarse compensation signal is converted to the frequency domain through FFT, so that constellation prejudgement is carried out; time domain partition on a prejudgement result and a coarse compensation result is carried out at the sametime; and, fine phase correction on the coarse compensation result of each partition is carried out by taking the prejudgement result as reference. The invention further discloses the RF pilot based CO-OFDM system phase noise compensation method. Compared with the existing subcarrier pilot based phase noise compensation scheme, the RF pilot based CO-OFDM system phase noise compensation method hasbetter ICI compensation performance; and in addition, due to fine compensation based on prejudgement and partition correction, the nonlinear phases shift resisting capability of the RF pilot is further improved.

A short-pulse fiber amplifier system (10) is designed so that nonlinear phase shifts and third-order dispersion are purposely introduced that compensate each other. In particular, the nonlinear phase shift accumulated in the amplifier is compensated by the third-order dispersion of the combination of a fiber stretcher (12) and a grating compressor (16). In the presence of third-order dispersion, an optimal nonlinear phase shift reduces the pulse duration, and enhances the peak power and pulse contrast compared to the pulse produced in linear propagation.

The coherent imaging method of 4f position based on the Michelson's interferometer is the nonlinear refractive method of 4f position coherent imaging measuring medium based on the Michelson's interferometer. It can solves the problem of data treating bother, nonlinear absorption of traditional 4f coherent imaging technology and the small deform range, high request for stability and complex data treating of Mach-Zehnder interference. The method is composed of the processes: one: starting and adjusting the device; two: collecting the image without image; three: collecting the linear image; four: collecting the nonlinear image; five: computing the linear penetrant ratio; six: computing the nonlinear phase movement; seven: computing the third-order nonlinear refraction coefficient.

A chirped-pulse fiber amplification method and system operates with large nonlinear phase shifts (as large as ˜20π or more). In this regime, the pulse spectrum is modified by strong self-phase modulation and gain shaping. With large-enough nonlinear phase shift, substantial spectral broadening occurs. The amplified spectrum can therefore be much broader than the spectrum that is obtained with small nonlinear phase shifts. The broader spectrum enables the formation of a shorter pulse, and the bandwidth generated in nonlinear chirped-pulse amplification can in fact be exploited to generate shorter pulses. Ultimately, this allows the generation of pulses shorter than the gain-narrowing limit of a fiber amplifier.

A fiber Chirped Pulse Amplification (CPA) laser system includes a fiber mode-locking oscillator for generating a laser for projecting to a fiber stretcher for stretching a pulse width of the laser. The fiber CPA laser further includes a multistage amplifier for amplifying the laser for projecting into a pulse shaper then to a compressor having a nonlinear phase generator for compensating high order dispersions and compressing the pulse width of the laser. The pulse shaper is further provided to minimize a nonlinear phase shift inside the multistage amplifier for reducing a Stimulated Raman Scattering (SRS

The invention provides an optical fiber parameter calculating method and device, and aims to obtain optical fiber parameters via calculation. The invention further provides a phase sensitive amplifier and a full-optical phase regeneration device, wherein the phase sensitive amplifier is used for regeneration of full-optical phase; the involved optical fiber is obtained by using the calculating method and the calculating device. The optical fiber parameter calculating method comprises the following steps: acquiring signal optical waves, first pumping optical waves and second pumping optical waves, performing four-wave mixing in an optical fiber of double-pump degeneracy PSA so as to generate four sideband-idle optical waves, establishing a 7-wave value model, and dissolving a coupling equation of the signal optical waves, and calculating so as to obtain vibration amplitude phase of the regenerated optical waves; adjusting non-linear phase shift and optical second-order dispersion coefficients, so as to obtain the minimum and optimal optical second-order dispersion coefficient corresponding to non-linear phase shift. The optical fiber is manufactured according to the parameter, the optical fiber is applied to PSA, then the PSA has relatively large GER and works in relatively small non-linear phase shift, and furthermore, a regeneration device of low power consumption and full optical phase can be obtained.

All-optical polarization rotation switch is disclosed. A linearly polarized probe light is split by a polarization beam splitter (PBS) into two orthogonal linear polarization components, which are coupled with respective ends of a nonlinear optical fiber in loop configuration. A linearly polarized control pump light is launched into one direction of the fiber. The probe light component co-propagating with the control light pulse undergoes a nonlinear phase shift due to cross phase modulation (XPM). The phase shift of the light co-propagating with the control pulse thus causes a rotation of the recombined light output from the PBS. The rotation is detected by using a polarizer. Exploiting XPM instead of the nonlinear birefringence enables the use of highly nonlinear PM fiber.

The invention relates to an 8-shaped passive lock mode impulse fiber laser, wherein another end of central coupler is connected to the polarization controller, the wavelength division multiplexer, the yttrium doping fiber, the light separator and the coupler, to form chamber; the non-linear light annular mirror is formed by connected single-mode fiber and coupler to form chamber; the couple input of wavelength division multiplexer has pump source. The invention has low impulse energy fluctuation and low cost. And the coupler is asymmetry arranged near the central coupler; and the annular mirror uses same fibers; the light transmitted reversed has different density after coupler to the light not passing coupler, and the non-linear phase shifts are different; and lights transmitted with same direction have same density when interfered in central coupler, therefore, the lock-mode effect is better.

The invention relates to a phase aperture which is used for a 4f phase coherence imaging system. The aperture body is composed of an annular light penetrating strip which is at the periphery side and a phase object which is at the center part. The invention is characterized in that the phase object is divided into two parts. The phase difference between one part of the phase object and the annular light penetrating strip is 2mPi plus Pi / 2, and the phase difference between the other part of the phase object and the annular light penetrating strip is 2nPi-Pi / 2. In the formula, m and n are integers. The measuring precision of the system can be increased in the range of a nonlinear phase shift of |PsiNL| being less than Pi by an improved phase aperture. For a positive nonlinear phase shift, the improvement of the sensitivity can be reached 1.72 times at the most degree. But for a negative nonlinear phase shift, the improvement of the sensitivity is especially obvious. When the formula PsiNL being equal to minus Pi is valid, the improvement of the sensitivity can be enhanced by 7.26 times.

A control method, which is applicable to a variety of network configurations, controls an optical transmission system to determine optimum optical input power to a transmission path for increased optical transmission quality. The optical transmission system has terminal stations, repeaters, dispersion compensation modules, and a dispersion compensation controller. The terminal stations transmit and receive an optical signal through an optical fiber transmission path. The repeaters are disposed in the optical fiber transmission path for amplifying the optical signal. The dispersion compensation modules are disposed in the terminal stations and the repeaters for compensating for dispersion of the optical signal. The dispersion compensation controller determines a target value for a nonlinear phase shift, which is an indication of a self-phase modulation caused by a transmission medium of the optical fiber transmission path, to have a maximum residual dispersion tolerance, and adjusts at least one of the input powers applied to transmission paths connected to the terminal stations or the repeaters and the input powers applied to the dispersion compensation modules to equalize the nonlinear phase shifts of paths in the optical transmission system to the target value.

An apparatus for and a method of pre-emphasis the launch power profile of a section in an optical network are provided. The method comprises the steps of measuring the output power at the output of the section, determining the predicted output power associated with a flat launch power profile using design characteristics of the section and determining the total power deviation between the measured output power and the predicted output power. The method also comprises the steps of determining the signal to noise ratio deviation and the nonlinear phase shift deviation as a function of the total power deviation, and pre-emphasis the launch power profile based on a function of the calculated signal to noise ratio deviations of each span and the calculated nonlinear phase shift deviations of each span, such that the sum of the nonlinear phase shift deviations and the sum of the signal to noise ratio deviations of each channel are reduced by an equal amount.

The invention discloses a high repetition frequency fiber laser based on the principle of a phase offset device and a control method. According to the invention, a high repetition frequency fiber laser forms a nonlinear amplifying loop mirror; a mirror and a beam splitter are used to divide a pulse into two lights, and the lights are rotated counterclockwise and clockwise respectively; Faraday rotation and a birefringent crystal form a phase shift unit; the first light and the second light produce phase difference of pi / 2; the first light and the second light are recombined to realize nonlinear phase-shift mode locking; the threshold for mode locking startup is greatly reduced; the repetition frequency is improved; the overall stability and reliability are improved; a fiber wavelength division multiplexing collimator is used to replace a conventional fiber wavelength division multiplexer and a fiber collimator; the Faraday rotating mirror of a thin-film magneto-optic material is used to replace a conventional optical fiber isolator or the free-space isolator of a crystal magneto-optic material, which greatly shortens the length of a fiber in the fiber laser; the laser system is simplified; the coupling power and the efficiency are improved; and the repetition frequency is improved.

A method and apparatus to linearize the phase shifts produced by the wavelength-varying driving mechanism of an interferometer used in phase shift interferometry for the measurement of multiple reflective surfaces first calibrates a sequence of physical values used as the input to the driving mechanism to produce a known linear or a known constant phase shift increment between any two adjacent interferograms. The calibration process, in essence, involves the determination of the sequence of physical values, such as the voltage change with respect to the time, through the process of iteration. This sequence then is used as an input to the phase shift driving mechanism for ongoing operation of the system, thereby compensating for non-linear characteristics of the system.

The invention discloses a nonlinear effect suspension method and system for a CO-OFDM (Coherent Optical Orthogonal Frequency Division Multiplexing) system. The nonlinear effect suspension method comprises the steps of: at a system sending end, for a random group, acquiring a conjugate symbol in phase conjugation with a pilot symbol so as to obtain a corresponding neighbor estimation group; carrying out carrier mapping on the pilot symbol, the conjugate symbol and a data symbol and sending a carrier to a system receiving end; at the system receiving end, carrying out frequency domain signal reduction on the carrier sent from the system sending end, and extracting the pilot symbol, the conjugate symbol and the data symbol; carrying out coherent superposition on the extracted pilot symbol andthe corresponding conjugate symbol so as to compensate a nonlinear phase shift in the pilot symbol; and estimating a nonlinear phase shift of the data symbol in the same neighbor estimation group byutilizing the extracted pilot symbol and the corresponding conjugate symbol, and carrying out compensation on the nonlinear phase shift of the data symbol. According to the invention, damage caused bya nonlinear effect in the CO-OFDM system can be effectively and comprehensively compensated in real time.

It is propose to use a DI-NOLM comprising an optical loop made of two spools of dispersive fibers with large effective area but of local dispersion of opposite sign and a HLN fiber in between. In this configuration according to the invention, the input optical signal needs to be initially chirped. A nonlinear phase shift is then generated between both counter propagating optical fields inside the HNL as the consequence of the peak power imbalance. Advantageously, it is possible to process RZ or RZ / DSPK with a rather large shape at half-way taking even more than 65% of bit time. This can be achieved without any alteration of the optical regeneration. Moreover, in this configuration by using the method according to the invention, the compensation dispersion is realized inside the DI-NOLM, and so it is not necessary to add a compensating dispersion state at this interferometer.

The invention discloses an all-optical logic gate based on a non-linear phase shift fiber bragg grating. A signal source is arranged and is connected with a first wavelength division multiplexer port I, a first wavelength division multiplexer port II is connected with a second optical isolator port I, a second optical isolator port II is connected with a third band-pass filter port I, a third band-pass filter port II is connected with a second non-linear phase shift fiber bragg grating input port I through a second optical circulator, an output port of the second non-linear phase shift fiber bragg grating is connected with a fourth band-pass filter port I, and a fourth band-filter port II is connected with a second wavelength division multiplexer; a first optical isolator is connected with a first band-pass filter port I, a first band-pass filter port II is connected with an input port I of a first non-linear phase shift fiber bragg grating through a first optical circulator, an output port of a first non-linear phase shift fiber bragg grating is connected with a second band-pass filter port I, and a second band-pass filter port II is connected with a third wavelength division multiplexer.

The invention relates to a method and an arrangement for determining the dispersion of an optical transmission link. By determining the signal quality, the bit error rate is measured for a modulated data signal depending on the modulation frequency of a noise signal (STS). The dispersion coefficient of the transmission link is calculated on the basis of the resulting discrete minima of the bit error rates. These measurements can take place advantageously during the operation of the data transmission. The method also provides additional information about the quality of the data transmission by determining the non-linear phase shift.

A system for all-optical signal regeneration is provided, which makes it possible to exhibit desired intensity noise suppressing function with respect to pulsed input signal light without increasing the injection current of semiconductor optical amplifiers even if the magnitude of nonlinear phase shift of the input signal light is less than π. The output light of the first delay interference unit is subjected to phase shift in the first nonlinear semiconductor waveguide and then, applied to the second delay interference unit along with the clock light. In the second delay interference unit, the first interfered light is generated from the output light while the second interfered light is generated from the clock light having an opposite logic to the input light. The second interfered light is subjected to phase shift by the first interfered light in the second nonlinear semiconductor waveguide and then, applied to the third delay interference unit. The third interfered light having an opposite logic to the input light is generated from the second interfered light in the third delay interference unit. The third interfered light is the output light of the system.

The invention discloses a fiber vibration signal detection device and a method. The device comprises a narrow band coherent light source, an optical switch, an optical annular device, a fiber sensing array, a first fiber coupler, a delay fiber, a connection fiber, a second fiber coupler, a first optical Kerr medium, a second optical Kerr medium, a third fiber coupler, a balancing detector and a data acquisition and control plate card. The method comprises steps of using the two optical Kerr media to carry out nonlinear phase shifting on two paths of interference light and then carry out interference; the signal acquisition and control plate card is used for controlling the optical switch to modulate narrow band light given out by the narrow band coherent light source to form pulse narrow band light; and by acquiring the output signals of the balancing detector, the size of the sensing signals is obtained. According to the invention, it is achieved that the sensing signals are amplified in case of not adopting an active amplified; phase position flexibility of the sensing signals is improved; response degree of the system is improved while complexity of a system signal processing device is reduced; and system cost is reduced.

The invention disclose a 'percent sign' counter passive mode-locking optical fiber laser, comprising an optical fiber amplifier and two non-linear optical fiber ring mirrors, wherein the two non-linear optical fiber ring mirrors are welded at an input port and an output port of the optical fiber amplifier to form a 'percent sign' counter structure. The two non-linear optical fiber ring mirrors and the optical fiber amplifier compose a F-P cavity which can realize an optical pulse output with stable line width; through the output of the non-linear optical fiber ring mirrors and by launching a feedback loop technology, the optical pulse output with stable line width can be realized; configurations of the non-linear optical fiber ring mirrors enable the light transited in the ring counter clockwise and clockwise to obtain different non-linear phase shift when reaching a coupler, only a phase shift difference rate of the central wavelength reaching pi first and a starting mode-locking forms.

The invention provides a saturable absorption mirror based on a highly nonlinear twin-core optical fiber. The saturable absorption mirror includes a single-mode optical fiber, high nonlinear twin-coreoptical fiber and mirror; Single-mode optical fiber comprises a core (A1) of a single-mode optical fiber and a cladding (A2) wrapped around the core of the single-mode optical fiber; The highly nonlinear twin-core optical fiber comprises two cores (B1) of the nonlinear twin-core optical fiber, a core (B2) and a cladding (B3) wrapped around the two cores; The optical signal is injected into the fiber core (B1) through a single-mode fiber coupling. The optical signal is reflected by a mirror at the other end of the highly nonlinear twin-core fiber, propagates backward along the direction of theincident fiber core and is outputted from the single-mode fiber. The invention increases the nonlinear phase shift of the optical signal in the cavity by adopting the highly nonlinear twin-core optical fiber, reduces the volume to enhance the compactness of the structure, and adjusts the saturation power by the fiber core distance of the adjustable nonlinear twin-core optical fiber, so as to increase the working stability of the laser under the condition of higher power damage threshold.