84 results about "Few mode fiber" patented technology

The invention discloses an optical fiber transmission image recovery method and device based on a complex amplitude regulation metasurface diffraction device, and the method comprises the steps: obtaining the complex amplitude distribution of each diffraction layer through the training of a diffraction neural network, designing a corresponding metasurface array, and preparing a cascaded metasurface diffraction device with a complex amplitude regulation function, deploying a cascade metasurface diffraction device to the far end of the multimode optical fiber and performing complex amplitude modulation on emergent circularly polarized light to realize high-resolution or high-sampling-rate image recovery; or an optical fiber transmission inverse matrix is solved by using an analytical method, and a corresponding metasurface array is designed, so that the single-layer metasurface diffraction device with a complex amplitude regulation and control function is prepared; and deploying the single-layer metasurface diffraction device to the far end of the few-mode optical fiber and carrying out complex amplitude modulation on emergent circularly polarized light to realize low-resolution or low-sampling-rate image recovery. Miniaturization of a multimode optical fiber imaging system can be realized, and the image recovery quality is effectively improved based on complex amplitude modulation of the metasurface diffraction device.

The invention discloses a vernier effect and Sagnac ring-based dual-parameter optical fiber sensor, which belongs to the technical field of optical fiber sensors and comprises a broadband light source SLED (1), a coupler (2), a sensing structure A (3), a circulator (4), a sensing structure B (5) and a spectrum analyzer (6). The device comprises a first single-mode fiber (301), a polarization-maintaining photonic crystal fiber (302), a few-mode fiber (303), a fiber Bragg grating (304), a second single-mode fiber (501), a first hollow-core fiber (502) and a second hollow-core fiber (503). Parasitic interference is avoided by grinding the end face of the hollow-core optical fiber, and the reliability of the sensor is improved; two transmission peaks appear on the fiber bragg grating inscribed on the few-mode fiber through different mode numbers in the few-mode fiber, and gas concentration and temperature sensitivity of two signals can be calculated by observing drifting of the transmission peaks; an optical vernier effect can be formed through superposition of a Sagnac interferometer formed by polarization-maintaining photonic crystal fibers and an F-P interferometer formed by hollow core dislocation, and the gas concentration and the temperature sensitivity of the sensor are improved. The sensor has the characteristics of high sensitivity, wide measurement range, simple structure, small size and the like.

The invention discloses a relay device and method for long-distance few-mode optical fiber communication, and belongs to the field of optical communication. According to the device, firstly, optical signals transmitted in a few-mode optical fiber are separated into a plurality of independent mode channels through a mode decomposition multiplexer; then, an adjustable light delay unit is configured in each channel, and compensation is carried out according to a difference mode group delay difference pre-calculated or actually measured by a few-mode optical fiber parameter; furthermore, a dimmable amplifier is used for amplifying the signal, power monitoring is carried out at the output end of the amplifier through an optical fiber beam splitter and a photoelectric detector, closed-loop feedback control is formed, and gain of each channel is adjusted in a self-adaptive mode to eliminate mode-dependent loss. According to the invention, signal distortion can be effectively suppressed in an optical domain, the complexity of digital signal processing of a receiving end is reduced, and the transmission distance and the transmission capacity of a few-mode optical fiber mode division multiplexing communication system are remarkably improved.

An optical communication system can include a multiplexer / demultiplexer. The multiplexer / demultiplexer can transfer a first optical data signal between a first single-mode fiber and a first propagation mode of a few-mode fiber. The first propagation mode can have a first effective refractive index. The multiplexer / demultiplexer can transfer a second optical data signal between a second single-mode fiber and a combination of a second propagation mode of the few-mode fiber and a third propagation mode of the few-mode fiber. The second propagation mode and the third propagation mode can have a same effective refractive index that differs from the first effective refractive index. During propagation within the few-mode fiber, the second optical data signal can couple bidirectionally between the second propagation mode and the third propagation mode, while being substantially isolated from the first optical data signal in the first propagation mode.

The invention belongs to the field of optical measurement and detection, and particularly relates to a coherence tomography wavefront measurement device and method based on optical fiber interconnection and point diffraction, the measurement device separates a fundamental mode and a high-order mode of test light through a few-mode optical fiber, the fundamental mode generates a reference spherical wave through point diffraction to serve as reference light, and the high-order mode serves as the test light; after the test light and the reference light are subjected to optical fiber coupling interference, an interference pattern is obtained by a detector, and wavefront error measurement and optimization are realized through wavefront calculation and correction. The method has high precision and high stability, and can realize rapid closed-loop feedback correction.

The application discloses a device and method for coexistence of bright-dark solitons based on a mode division multiplexing resonant cavity, and relates to the technical field of lasers.The device for coexistence of bright-dark solitons based on the mode division multiplexing resonant cavity comprises an erbium-doped fiber amplifier, a first optical coupler, an acousto-optic frequency shifter, a second optical coupler, a third optical coupler, a first mode selection coupler, a second mode selection coupler and a fiber ring resonant cavity, and the fiber ring resonant cavity is a non-uniform dispersion few-mode fiber.The device and method for coexistence of bright-dark solitons based on the mode division multiplexing resonant cavity can realize stable coexistence of bright-dark solitons.

The invention discloses a bending endoscopic imaging method and system based on a few-mode optical fiber, and belongs to the technical field of optical fiber imaging. According to the method, an MNIST handwritten digital image is loaded through a digital micromirror device (DMD), a speckle pattern is generated through few-mode optical fiber transmission, image restoration in a bending state is achieved through a deep learning model, and reconstruction effects under different bending degrees are quantized through a Dice coefficient. The system comprises a light beam collimation module, a pattern loading module, an image transmission module and an image acquisition-processing module. The image transmission module adopts a step refractive index few-mode optical fiber, and mode coupling caused by bending is inhibited by increasing the effective refractive index difference between modes; and the image acquisition-processing module is combined with a shallow U-shaped convolutional neural network to reconstruct a speckle pattern acquired by the CCD camera. While miniaturization of the probe is ensured, the imaging quality in a bending environment is remarkably improved, and the probe is suitable for miniaturized high-resolution imaging scenes such as medical endoscopes and the like.

The application discloses a spatial-mode hybrid diversity receiving system for spatial laser communication. After a transmitting light beam passes through atmospheric turbulence, diffusion and distortion and other phenomena occur, spatial diversity and mode diversity are combined at a receiving end, an array of M receiving antennas is used to receive the diffused light beam to perform spatial diversity, a few-mode fiber supporting N modes is connected after each receiving antenna, high-order modes are converted into base modes by a mode demultiplexer and then output to a single-mode fiber to perform mode diversity, then a total of M*N branch signals are converted into electric signals by photoelectric detection modules, and finally, the branch signals are combined after digital signal processing. The application combines spatial diversity and mode diversity, can effectively compensate the influence of atmospheric turbulence on laser transmission, and is beneficial to spatial laser communication under more severe channel conditions.

The invention provides a cooperative communication and sensing optical transmission system based on an elliptical core few-mode optical fiber. The system comprises a transmitting end, the elliptical core few-mode optical fiber and a receiving end. The transmitting end converts a digital signal into a mode encoding sequence through a mode encoder and couples the mode encoding sequence into the elliptical core few-mode optical fiber; the elliptical core few-mode optical fiber effectively reduces crosstalk between modes by utilizing a relatively large effective refractive index difference between different mode groups of the elliptical core few-mode optical fiber, and effectively improves the security of information transmission by utilizing a mode coding mode; the receiving end detects the position of the end face of the output optical fiber through an imaging system and a camera, compensates the position of the end face of the optical fiber through an electric displacement table to improve the mode demodulation performance of the receiving end, and recovers a mode coding sequence into original digital information through a mode decoder and a signal processor. According to the invention, the security of the optical fiber communication system can be effectively improved, crosstalk between modes is reduced, the robustness of mode demodulation of the receiving end is increased, and the performance of the space division multiplexing optical fiber communication system is effectively improved.

The invention relates to the technical field of optical communication, and discloses a mode diversity receiving system and method based on all-fiber coherent synthesis, and the system comprises a photon lantern receiving module, a cascade double-coupling module, a signal monitoring module, a control and feedback module, and a coherent detection module. Spatial optical signals influenced by atmospheric turbulence are firstly coupled into the few-mode optical fiber of the photon lantern to be received, multi-mode optical signals are excited and converted into multiple paths of single-mode signals, then coherent combination is carried out through the cascade double-coupling module, and the signal monitoring module monitors a beam combination result in real time. And the control and feedback module actively controls and compensates the phases of the multiple paths of single-mode signals, and photoelectric conversion and digital signal processing of the combined optical signals are completed by the coherent detection module. The influence of atmospheric turbulence on power imbalance in optical domain mode diversity is eliminated through active control and cascade double coupling, so that mode diversity gain is obtained, and adaptability of a space laser communication or radar system to the atmospheric turbulence is remarkably enhanced.

The application discloses a few-mode fiber double-cascaded mode converter and a high-power few-mode fiber laser. A core base mode and a core high-order mode converter and a core high-order mode and a cladding mode converter are cascaded on the few-mode fiber. The refractive index modulation distribution of the core base mode and the core high-order mode converter is uniformly distributed in the core center, and is used for coupling the core base mode to the core high-order mode. The refractive index modulation distribution of the core high-order mode and the cladding mode converter is distributed at the junction of the core and the cladding, and is used for coupling the core high-order mode to the cladding to form loss. The few-mode fiber double-cascaded mode converter is connected before an output end cap of the high-power few-mode fiber laser, and can inhibit stimulated Raman scattering in the large-mode-field few-mode fiber laser, so as to improve the output performance of the fiber laser.

The invention relates to a multi-parameter fusion distributed optical fiber sensing system and method based on a few-mode optical fiber, and relates to the technical field of distributed optical fiber sensing, and the system is characterized in that emergent light of a laser is subjected to beam splitting and is respectively processed; part of the light is modulated to generate LP01 and LP11 mode light for detection, and the other part of the light generates Rayleigh local oscillation light and Brillouin local oscillation light. The detection light is combined and then injected into the sensing optical fiber to generate backscattered light. And the scattered light is separated into LP01 Brillouin scattered light, LP11 Brillouin scattered light and LP11 Rayleigh scattered light through a mode demultiplexer. And performing beat frequency processing on the different types of scattered light and the corresponding local oscillation light by using a balance detector to obtain a first low-frequency signal, a second low-frequency signal and a beat frequency signal. The data processing module analyzes the signals and can obtain a Brillouin frequency shift spectrum and a vibration signal frequency spectrum reflecting a vibration event. The method has the effect of realizing high-precision measurement.

The invention discloses a high-order Poincare light beam characterization measurement method and a high-order Poincare light beam characterization measurement device. According to the method, all parameter information of a high-order Poincare beam is measured based on centroid ellipse information of different polarization components of an interference field. The absolute value of the difference between the reference light and the measured light mode-based orbital angular momentum topological charge number is 1. The rotational symmetry of two paths of cross-polarization interference fields obtained after coaxial interference is broken, the center of mass deviates from the center of a light beam, and the center of mass moves to form an elliptical orbit under the condition of dynamic interference. And synchronously detecting the centroid tracks of the two paths of dynamic interference fields to obtain two centroid ellipses. And adding the two centroid ellipse coordinates and averaging to obtain a third associated ellipse. All Poincare sphere parameters can be calculated according to nine ellipse parameters of the three ellipses, so that the light beam is positioned and displayed on the three mixed Poincare spheres. The device breaks through the measurement limitation of a traditional polarization analyzer, can be used for detecting the dynamic evolution of a few-mode optical fiber high-order mode group, and assists the development of optical sensing and optical measurement technologies.

The application discloses a fiber magnetic field and temperature measuring device and method based on a cascade MZI, and relates to the technical field of optical fiber sensing. The device comprises a broadband light source, a sensor and a spectrum analyzer. The sensor comprises a quartz tube and a first single-mode optical fiber, a first few-mode optical fiber, a magnetic fluid filled side-hole optical fiber, a UV glue film coated hollow-core optical fiber, a second few-mode optical fiber and a second single-mode optical fiber which are sequentially fused. The fiber core and the magnetic fluid cavity in the magnetic fluid filled side-hole optical fiber constitute a first MZI. The hollow-core fiber core and the second cladding in the UV glue film coated hollow-core optical fiber constitute a second MZI. The first few-mode optical fiber expands the light beam introduced by the first single-mode optical fiber, and then introduces the light beam into the second few-mode optical fiber through the first MZI and the second MZI for coupling. The coupled light beam is demodulated, a coefficient matrix is used for calculation, and the dual-parameter measurement of the magnetic field and the temperature is realized. The application aims to realize the simultaneous detection of the dual parameters of the magnetic field and the temperature, and has high sensitivity.

The invention discloses a central concave type multi-layer doped gain-balanced few-mode optical fiber structure, which is characterized in that each layer structure in an optical fiber is of a bull's-eye structure on the cross section of the optical fiber and shares the same center, and each layer sequentially comprises a low-refractive-index fiber core, a high-refractive-index fiber core, a groove and a cladding from inside to outside. According to the embodiment of the invention, a mode of combining a central concave type refractive index design and multi-layer doping is adopted, and overlapping integral factor differences among all transmission modes are reduced by adjusting distribution characteristics of all mode fields in the optical fiber, so that similar signal gains of all modes are realized, and a relatively excellent gain equalization characteristic of the amplifier is obtained. The optical fiber structure design can also increase the effective refractive index difference of each mode to a certain extent, reduce the coupling and crosstalk between the modes, and realize the high-purity gain of the few-mode optical fiber amplifier.

The invention belongs to the technical field of few-mode optical fibers, and discloses an ultralow differential mode group delay few-mode optical fiber and a preparation method thereof. The ultralow differential mode group delay few-mode optical fiber provided by the invention comprises a core layer structure, an inner cladding layer structure and an outer cladding layer from inside to outside, the core layer structure comprises a first core layer and a second core layer from inside to outside; the two core layers are provided with gradient sections, the distribution index alpha 1 of the first core layer is 1.5-1.9, and the distribution index alpha 2 of the second core layer is 1.4-1.9; the minimum relative refractive index difference 1 of the first core layer is 0.3% to 0.6%; the maximum relative refractive index difference of the first core layer and the maximum relative refractive index difference of the second core layer are the same and marked as 2, 2 is 0.6%-0.9%, and 2 > 1; the second core layer has a minimum relative refractive index difference 3 of-0.2% to-0.1%. According to the invention, extremely low differential mode group delay can be realized.

This invention provides a mode-division multiplexing (MDF) system, method, device, and storage medium, relating to the field of optical communication technology. The MDF system includes at least: multiple cascaded optical fiber transmission units across multiple spans and a central controller. Each optical fiber transmission unit includes multimode or few-mode fiber and a mode adjustment unit. The mode adjustment unit calculates the transmission parameters of the optical fiber transmission unit and sends these parameters to the central controller. The central controller acquires the transmission parameters of the optical fiber transmission units in each span, generates a target mode round-robin strategy for the corresponding span, and sends it to the mode adjustment unit to update the optical signal module. The central controller adaptively selects the target mode round-robin strategy based on the real-time transmission environment, adaptively adjusting each span to reduce differential mode group delay (DMD) and mode-dependent loss (MDL), adapting to different span lengths and different transmission environments, and improving the transmission performance of multimode or few-mode fiber.

The present invention provides a three-band mode multiplexing self-matching photon lantern and its manufacturing method, belonging to the field of optical communications. The photon lantern comprises: a fiber array, a transition region, and a few-mode port connected in sequence. The fiber array comprises a predetermined number of 980nm single-mode fibers with cladding, a single 1310nm few-mode fiber with cladding, and a single 1550nm few-mode fiber with cladding, placed in a quartz capillary tube. The fiber array is the portion that remains unchanged after adiabatically tapering to a predetermined length according to a predetermined stretch ratio. The transition region is the portion that changes shape after tapering, and the few-mode port is the port portion that changes shape after tapering. The photon lantern can achieve selective mode conversion at the 980nm wavelength, maintain the 1550nm and 1310nm wavelength modes, and transmit low-loss closed-loop signals. It can be used to construct a fiber ring laser cavity, enabling direct oscillation and output of multiple high-order modes within the all-few-mode fiber ring laser cavity, thus avoiding single-mode and few-mode incompatibility issues.

A sourceless co-packaged optical-electrical chip can include a plurality of different optical transceivers, each of which can transmit to an external destination or internal components. Each of the transceivers can be configured for a different modulation format, such as different pulse amplitude, phase shift key, and quadrature amplitude modulation formats. Different light sources provide light for processing by the transceivers, where the light source and transceivers can be configured for different applications (e.g., different distances) and data rates. An optical coupler can combine the light for the different transceivers for input into the sourceless co-packaged optical-electrical chip via a polarization maintaining media (e.g., polarization maintaining few mode fiber and polarization maintaining single mode fiber), where another coupler operates in splitting mode to separate the different channels of light for the different transceivers according to different co-packaged configurations.

The utility model discloses a kind of double-parameter optical fiber laser sensors based on Sagnac ring cascaded liquid phase filling MZI, belong to optical fiber sensor technical field, by LD pumped laser source (1), wavelength division multiplexer (2), holmium-doped optical fiber (3), optical circulator (4), sensing probe A (5), first coupler (6), sensing probe B (7), second coupler (8), optical spectrum analyzer (9), first single-mode optical fiber (501) polished in side edge, large core diameter hollow optical fiber (502) fills PDMS (503), few-mode optical fiber (504), fiber bragg grating (505), second single-mode optical fiber (506), third single-mode optical fiber (701), first panda polarization maintaining fiber (702), second panda polarization maintaining fiber (703), fourth single-mode optical fiber (704);The utility model can effectively improve the sensitivity of device to temperature by hollow optical fiber filling PDMS;By panda polarization maintaining fiber rotation shaft fusion splicing makes that interference phase difference amplification, spectral line drift is more obvious, so improve the sensitivity of device to temperature;Different reflection peak signals of few-mode optical fiber grating and Sagnac interference spectrum signals can establish sensitivity matrix to realize double-parameter measurement to temperature and strain, with excellent reliability and stability.

The invention relates to the technical field of optical fiber transmission, and particularly discloses a low-crosstalk few-mode optical fiber structure optimization design method based on a genetic algorithm, and the method comprises the steps: determining a fixed structure parameter of a few-mode optical fiber, and setting an optimization range of a to-be-optimized groove structure parameter; within the optimization range, randomly generating N groups of trench structure parameters to form an initial population; aiming at each group of groove structure parameters in the initial population, based on a coupling mode theory, calculating a corresponding inter-mode crosstalk value under a preset bending condition; screening out M groups of parameters with high fitness from the current population as excellent individuals according to the crosstalk value; performing crossover and mutation operation on the excellent individuals to generate a new generation of population; outputting a trench structure parameter corresponding to the lowest crosstalk value in the previous population; according to the method, the deformation-crosstalk mapping relation can be quantified, and the optical fiber structure can be guided to meet the mechanical reliability requirement of benchmarking with the single-mode optical fiber while keeping low crosstalk.

The invention belongs to the technical field of optical fiber communication and optical devices, and provides an ultrahigh-channel-number orbital angular momentum mode converter utilizing a few-mode optical fiber hybrid structure aiming at the problem that an orbital angular momentum mode converter based on a spiral long-period optical fiber grating has certain limitation on the number of channels or the frequency band covered by the channels at present. The orbital angular momentum mode converter is composed of two sections of graded-index few-mode optical fibers inscribed with spiral long-period fiber gratings and a section of step-index few-mode optical fiber. The orbital angular momentum mode converter provided by the invention can generate ultrahigh orbital angular momentum mode channels under wide bandwidth, and the channel interval can be flexibly controlled by changing the length of the step refractive index optical fiber. In addition, the periods of the two spiral long-period fiber gratings are reasonably designed, and multi-channel orbital angular momentum mode conversion of different orders can be achieved. The device is simple in structure, convenient to manufacture and high in reliability, and has certain practicability.

An integrated optical diversity receiving device addresses the high power consumption problem of correcting for phase distortion and beam pointing errors in existing free-space optical communications, belonging to the field of optical communications. The invention comprises: free-space light focused by a lens is received by a multimode / few-mode optical fiber; the multiple modes of light beams received by the multimode / few-mode optical fiber enter a photon lantern; the photon lantern performs mode demultiplexing and is then coupled into a single-mode optical fiber array; each light beam in the single-mode optical fiber array enters a polarization splitter / rotator / combiner through an edge coupler; the polarization splitter / rotator / combiner separates the incoming light beams into transverse electric (TE) and transverse magnetic (TM) modes, then rotates the separated TM polarization state light to a TE polarization state; the rotated TE polarization state light is combined with the separated TE polarization state light before entering an MZI network; the MZI network is used to achieve optical coherent beam combining; and a control circuit controls the combining of the light beams in the MZI network.

An object is to provide a differential mode delay measurement device and a method thereof capable of measuring a DMD with a simple configuration even when an FMF to be measured is a long distance.A differential mode delay measurement device 301 according to the present invention includes a light source 11 configured to output a coherent light beam having an optical frequency changed with a predetermined modulation period, a branching element 12 configured to bifurcate the light beam; a light incidence unit 13 configured to excite one of the light beams in a plurality of modes, cause the one of the light beams to enter one end of an optical fiber to be measured 51 that is a few-mode optical fiber, and input the other of the light beams into one end of a reference optical fiber 52 in a single mode; an image sensor 15 configured to observe an interference light beam between a measurement light beam emitted from the other end of the optical fiber to be measured 51 and a reference light beam emitted from the other end of the reference optical fiber 52; and an arithmetic unit 16 configured to detect a peak of the interference light beam appearing when the modulation period is changed, and measure a differential mode delay based on a period of the peak and an electric field distribution of the interference light beam at the peak.

The invention discloses a few-mode optical fiber multi-wavelength and multi-mode mixed mode decomposition device and decomposition method based on multi-wavelength lensless coherent modulation imaging, and the method comprises the steps: exciting a few-mode optical fiber to be detected through a multi-wavelength laser source, and modulating a mixed wavelength light field outputted by the optical fiber through a binary random amplitude plate; a single-frame diffraction pattern is collected by a detector; simultaneously reconstructing complex amplitude distribution of each wavelength component in a modulation plane from a single diffraction pattern by using a low-rank mixed state reconstruction algorithm containing frequency domain constraint; then constructing and calculating a virtual 4f system, and propagating a complex amplitude value of the modulation plane to an optical fiber end face to obtain amplified optical fiber end face complex amplitude distribution; and finally, space alignment is optimized in combination with a gradient descent algorithm, and modal coefficients under all wavelengths are extracted through modal projection. According to the method, the limitation that a traditional method can only perform single-wavelength analysis or is influenced by dispersion is overcome, and rapid, accurate and calibration-free decomposition of a multi-wavelength and multi-mode optical fiber light field under single exposure is realized.

The utility model discloses a double-parameter optical fiber sensor based on a conical few-mode fiber grating, which belongs to the technical field of optical fiber sensors and comprises a broadband light source (1), a sensing structure (2) and a spectrum analyzer (3). The sensing structure (2) comprises a first single-mode fiber (201), a coreless fiber (202), a conical few-mode fiber grating (203) and a second single-mode fiber (204); more cladding modes are generated through mode field mismatch of the single-mode optical fiber and the coreless optical fiber and bending of a conical area, the double-parameter sensitivity of the sensor is improved, and two transmission characteristic peaks appear on the fiber bragg grating inscribed on the few-mode optical fiber by using different mode numbers in the few-mode optical fiber. The reliability and repeatability of the sensor are greatly improved, the corresponding double-parameter sensitivity can be respectively calculated by observing the position change of an interference spectrum and a transmission characteristic peak, and a sensitivity matrix is further established, so that the simultaneous measurement of double parameters is realized. The sensor has the characteristics of high sensitivity, strong reliability, strong anti-interference capability, small size, simplicity in manufacturing and the like.

This invention discloses a method and system for spectral characterization of few-mode fiber Bragg gratings based on lightweight adaptive control. The method includes: clarifying the multimode reflection characteristics and feedback mapping theoretical basis of the few-mode fiber Bragg grating; constructing an adaptive feedback closed-loop device containing the few-mode fiber Bragg grating based on the multimode reflection characteristics and feedback mapping theoretical basis; performing adaptive locking for different proportions of higher-order modes of the few-mode fiber Bragg grating through the adaptive feedback closed-loop device to characterize the evolution of the few-mode fiber Bragg grating and obtain a reflection spectrum dataset under different proportions of higher-order modes; and establishing a quantitative transfer matrix of the spectral characteristics and mode ratios of the few-mode fiber Bragg grating based on the reflection spectrum dataset.

The present invention provides an optical fiber (100) (i.e., a few-mode optical fiber (100) comprising: at least three consecutive up-doped regions (i.e., core region) (102); and a cladding region (104) surrounding the at least three consecutive up-doped regions (102). In particular, the at least three consecutive regions (102) comprising a first up-doped region (106) having a first maximum refractive index (n1max), a second up-doped region (108) having a second maximum refractive index (n2max), and a third up-doped region (110) having a third maximum refractive index (n3max) where n2max>n3max>n1max. Further, the optical fiber (100) is constructed to allow only LP01 mode of optical light and LP11 mode of optical light to propagate through the few-mode optical fiber (100) and possesses high effective area and low Differential Mode Delay.

The invention discloses a few-mode optical fiber multi-damage parameter single-end synchronous measurement method and a few-mode optical time domain reflectometer thereof, and belongs to the technical field of optical fiber characteristic measurement. The method comprises the following steps: injecting an optical pulse into a few-mode optical fiber to be detected, and obtaining back Rayleigh scattering signals in multiple modes; carrying out wavelet transform denoising on the obtained backward Rayleigh scattering signal; processing the curve of the denoised back Rayleigh scattering signal by adopting a splicing algorithm so as to eliminate a front-end saturation blind area; differential mode group time delay is measured based on a Fresnel reflection peak single end, the feature position of the Fresnel reflection peak at the tail end of each mode curve is positioned, and the differential mode group time delay is calculated according to the position difference; and synchronously calculating a mode coupling coefficient and mode correlation loss based on the processed curve data. According to the invention, the measurement accuracy of the differential mode group delay is improved.

The present invention provides an information measurement method, apparatus, and device, wherein the information measurement device includes: a light source, an intensity modulator, a mode converter, and a mode orientation polarization perturbator connected in sequence; a light detector connectable to the output end of the few-mode fiber to be measured; a computing unit connected to the light detector via a signal collector; the mode orientation polarization perturbator connectable to the input end of the few-mode fiber to be measured; the intensity modulator is also connected to a sine wave generator; the intensity modulator modulates the sinusoidal radio frequency signal generated by the sine wave generator onto the linearly polarized laser emitted by the light source to form a modulated optical signal; the mode orientation polarization perturbator continuously perturbs the spatial orientation and polarization state combination of the degenerate modes traversing the optical signal; and the computing unit determines the signal broadening factor information of the few-mode fiber to be measured based on the signal collected by the signal collector. This solution solves the existing problem of being unable to accurately and simultaneously measure the differential mode delay and chromatic dispersion of the degenerate mode.