53 results about "Few mode fiber" patented technology

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 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 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 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 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 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 application aims to provide an LPFG and an optical transmission system in which a mode conversion amount is independent of a polarization wave state and an electric field distribution. The LPFG of the present application is a cavity row (25-1, 25-2) of cavities 15 arranged in parallel with a center axis z and periodically at positions away from the center axis z in a core region 11 of a few-mode optical fiber 10. Each cavity row (25-1, 25-2) is located at a different position in a length direction of the few-mode optical fiber 10 (a position in the z direction is different), and the cavity rows (25-1, 25-2) are located at positions shifted by 90° on a cross section with the center (intersection of the x axis and the y axis) of the cross section of the core region 11 as a reference.

This invention discloses a cable partial discharge detection system based on a photonic lantern and few-mode optical fiber, comprising a few-mode optical fiber setting module, a multi-mode partial discharge detection module, a signal fusion module, and a partial discharge discrimination module. The few-mode optical fiber setting module winds the few-mode optical fiber onto the power cable to be tested with a predetermined number of turns. The multi-mode partial discharge detection module performs multi-mode partial discharge detection on the cable to obtain multi-mode partial discharge detection values. The signal fusion module weights and fuses the multi-mode partial discharge detection values ​​obtained from the multi-mode partial discharge detection module to obtain the final cable partial discharge detection data. The partial discharge discrimination module inputs the final cable partial discharge detection data into a predetermined partial discharge criterion to determine whether partial discharge has occurred at the current monitoring point. This invention also has significant advantages such as strong practicality and wide applicability.

The invention discloses a few-mode sapphire derived fiber bragg grating for inhibiting mode mutual coupling peaks and a manufacturing method of the few-mode sapphire derived fiber bragg grating, and belongs to the technical field of special fiber bragg grating preparation. The sapphire-derived optical fiber is a few-mode optical fiber with the refractive index distributed in a gradually-changing mode, aiming at the problem of mutual coupling of an LP01 mode and an LP11 mode of the fiber bragg grating, the low-refractive-index matching oil is selected, the beam expanding effect of a cylindrical lens system formed by the low-refractive-index matching oil and the sapphire-derived optical fiber on incident femtosecond laser is effectively weakened, and therefore the optical fiber bragg grating has the advantages that the optical fiber bragg grating is high in optical fiber Therefore, a refractive index modulation area with a small size is formed in the fiber core. According to the method, the mutual coupling peak of the LP01 mode and the LP11 mode can be effectively inhibited while the high reflectivity of the self-coupling peak of the LP01 mode is kept, the overlapping and crosstalk of spectrums in the multiplexing process of a plurality of gratings are reduced, the sensing resolution precision is improved, and the application requirements of a multiplexing optical fiber sensing system are met.

This invention belongs to the field of optical fiber testing and sensing technology, specifically relating to a method for identifying faults and disturbances in few-mode optical fibers using Raman-enhanced time-domain reflectometry (TDDR). The method includes: signal transmission based on pulse coding and mode-selective excitation; signal-to-noise ratio enhancement based on distributed Raman amplification; mode demultiplexing and mode field detection; coded demodulation and reconstruction using a multi-mode few-mode optical TDDR; multi-dimensional fault identification based on mode-dependent loss and coupling characteristics; and multi-mode differential and high-precision positioning based on digital signal processing. This invention targets high-capacity communication and distributed sensing systems using few-mode fibers. It solves the problem of detecting weak inter-mode scattering signals by coordinating pulse coding gain and distributed Raman optical gain. Subsequently, it utilizes the unique mode-dependent loss and inter-mode energy transfer characteristics of few-mode fibers for joint decision-making, providing highly sensitive, multi-dimensional optical fiber link health monitoring capabilities. This method has great potential and application prospects in the operation and maintenance of next-generation space-multiplexed optical networks.

The application discloses a high-efficiency optical waveguide chip-few-mode fiber coupler. The coupler comprises a few-mode fiber-multimode waveguide mode spot conversion module on a low-contrast conversion chip, a polarization-insensitive mode multiplexing / demultiplexing module, a low-high-contrast waveguide mode spot conversion module and a polarization control module on a high-contrast chip. 2n linear polarization modes of the few-mode fiber are coupled into a multimode waveguide through the end face of the few-mode fiber-multimode waveguide mode spot conversion module, and then are demultiplexed into n base modes through the mode multiplexing / demultiplexing module, and then are coupled into n high-contrast waveguides through the low-high-contrast waveguide mode spot conversion module to obtain TE0 / TM0 mode pairs, and finally are divided into 2n linear polarization modes of the high-contrast waveguide through the polarization control module. The application can realize high-efficiency coupling of linear polarization modes in the few-mode fiber and linear polarization modes in the high-contrast optical waveguide chip, has the advantages of large bandwidth, large tolerance, low crosstalk, semiconductor process compatibility and the like, and effectively solves the problem of multimode coupling from the optical fiber to the chip.

The invention discloses a simulation method and device for a mode selection coupler, equipment, a storage medium and a product. The simulation method comprises the steps of constructing a side-cast single-mode fiber geometric model, a side-cast few-mode fiber geometric model and a side-cast mode selection coupler geometric model; determining a light source file based on the side-cast single-mode fiber geometric model, and determining a path monitor input mode file based on the side-cast single-mode fiber geometric model and the side-cast few-mode fiber geometric model; and performing mode selection coupler simulation according to the light source file, the path monitor input mode file and the geometric model of the side-cast mode selection coupler to obtain a simulation result. Compared with an existing mode of manually drawing a plurality of models, calculating a light source file and inputting a mode file into a path monitor for simulation, the mode provided by the invention can realize automatic operation of a simulation process, and on the premise of ensuring the calculation precision, manual operation steps are reduced, the simulation time is shortened, and the overall simulation efficiency is improved.

The invention provides a wavelength division multiplexer, a manufacturing method thereof and a power amplification module, and the manufacturing method of the wavelength division multiplexer comprises the steps: stripping and wiping coating layers of a pair of few-mode optical fibers; corroding a part of thickness of the cladding of the few-mode optical fiber by using an acid solution; tapering the model of the middle part of the pair of processed few-mode optical fibers to form a fused cone; one ends of the pair of few-mode optical fibers form an input optical fiber and a terminal optical fiber; the other ends of the pair of few-mode optical fibers form a first output optical fiber and a second output optical fiber; and then three-stage packaging processing is carried out to prepare the wavelength division multiplexer. The power amplification module comprises a second-stage amplification assembly, a third-stage amplification assembly and an output assembly which are connected in sequence; the output assembly comprises at least two wavelength division multiplexers which are connected in series. According to the invention, pretreatment such as coating layer stripping, cladding corrosion and the like is carried out on the few-mode fiber, the fused cone is formed in combination with tapering treatment, and a multi-layer packaging structure is adopted, so that the insertion loss is reduced, and the channel isolation of optical signals is improved.

The invention relates to the technical field of optical components, in particular to a coupling fiber grating sensor based on a high-order mode, a manufacturing method and a detection device. Comprising a few-mode fiber; a few-mode core shift small-period long-period fiber bragg grating is arranged at the cross section in the few-mode fiber in a core shift mode, the few-mode core shift small-period long-period fiber bragg grating is arranged in the axial direction of the few-mode fiber, and the deviation distance between the few-mode core shift small-period long-period fiber bragg grating and the fiber core center of the few-mode fiber is 0-11 [mu] m. The method can realize automatic detection of low-concentration heavy metal ions and temperature, and is good in stability, high in selectivity and good in repeatability.

The embodiment of the utility model discloses a mode filtering optical fiber and a laser device thereof. The mode filtering optical fiber comprises a fiber core, an inner cladding and an outer cladding, wherein the inner cladding comprises a matrix material and dielectric cylinders; the dielectric cylinders surround the fiber core and are periodically arranged in the matrix material in multiple layers, the dielectric cylinders on the inner layer are arranged in a regular hexagon shape, the dielectric cylinders on the outermost layer comprise four dielectric cylinder groups, and each dielectric cylinder group comprises three dielectric cylinders; a mode capable of being transmitted in a microstructure area formed by the dielectric cylinders and the matrix material forms a super-mode group, and an interval formed by the effective refractive index of the lowest-order mode and the effective refractive index of the highest-order mode in the super-mode group is a super-mode group interval. And the leakage loss of the fiber core mode in the super mode group interval is greater than that of other fiber core modes of which the effective refractive index is not in the super mode group interval. According to the utility model, large-mode-field and pure-fundamental-mode transmission is realized, and the dielectric cylinders are regularly arranged, so that the optical fiber is formed by tapering after being stacked in a rod shape, and the transmission mode of the few-mode optical fiber is effectively controlled.