171 results about "Higher order mode" patented technology

A TE based on polymer optical waveguide 10 ‑TE 00 / TE 20 ‑TE 10 This compact mode converter belongs to the field of photonic integration technology. It consists of a substrate, a lower cladding, a core waveguide, and an upper cladding. The core waveguide is covered by the upper cladding. The lower and upper claddings are EpoClad, and the core waveguide is EpoCore, with the same height. It is constructed by sequentially connecting an input straight waveguide, a first intermediate asymmetric tapered waveguide, a second intermediate asymmetric tapered waveguide, a third intermediate asymmetric tapered waveguide, a fourth intermediate asymmetric tapered waveguide, a fifth intermediate asymmetric tapered waveguide, an output symmetric tapered waveguide, and an output straight waveguide. When passing through the intermediate asymmetric tapered waveguide, different mode components propagate with different effective lengths, causing different phase changes, ultimately resulting in the target mode. This increases channel transmission capacity and can be used in mode add / drop multiplexers (MADMs) and high-order mode filters.

The invention relates to the technical field of laser beam shaping, discloses an active test method and system for a circuit breaker, and is used for solving the problem that the self-adaptive shaping capability of a CO2 laser beam is difficult to improve by the existing method. Firstly, a stable light path is constructed, and the stability of the light path is ensured through mechanical limiting, a thermal management module and multi-stage optical alignment; then low-power calibration is carried out, a deformable mirror initial driving table is generated through a least square inversion algorithm, and a flat-topped beam reference is established; data are collected through a wavefront sensor, a high-order mode is reconstructed, the voltage of a deformable mirror is dynamically refreshed, and wavefront control and scanning motion synchronization is ensured in combination with scanning galvanometer time sequence synchronization, closed-loop control and exception handling; monitoring the temperature of the deformable mirror, starting water-cooling adjustment, and correcting the driving table to cope with the heat effect; finally, a safety system is constructed, laser power, wavefront distortion and deformable mirror stroke parameters are monitored, dry gas purging is conducted on the diffractive optical element regularly, and safety guarantee and performance verification of the whole process are achieved.

An optical device includes a transition unit in which a first waveguide and a second waveguide are disposed in an overlapped manner such that a magnitude relationship of an effective refractive index between the vertical modes propagating the first waveguide and the vertical modes propagating the second waveguide is inverted at the positions of input and output. The transition unit allows, at the input, the second waveguide to be a single mode waveguide and allows, at the output, the second waveguide to be a multi-mode waveguide through which TM0 light in the maximum vertical mode and light in a higher-order mode propagate. The optical device includes a removing unit that allows the second waveguide to be a single mode waveguide through which the TM0 light propagates by removing the light in the higher-order mode from the light received from the transition unit.

The invention provides a wide-ridge single-mode semiconductor laser and a manufacturing method thereof.The laser comprises an N electrode, a substrate layer, an epitaxial structure and a P electrode which are stacked in sequence, a grating layer is arranged in the epitaxial structure, and a grating is etched in the portion, close to the center, of the grating layer; the epitaxial structure is partially etched with the area where the grating is located as the center, a ridge-shaped structure is obtained, and the width of the ridge-shaped structure is larger than that of the grating. The grating is arranged in the epitaxial structure, and the high-order mode lasing of the wide-ridge semiconductor laser can be inhibited by regulating and controlling the feedback effect of the grating on different modes of the semiconductor laser, so that the quality of a fundamental mode beam is improved.

The invention discloses a few-mode hollow-core anti-resonance optical fiber based on a spiral cladding and a preparation method thereof. The optical fiber structure is sequentially divided into a hollow-core fiber core area, a cladding area and an outer sleeve area from inside to outside; the cladding area is formed by arranging a plurality of spiral anti-resonance structure units along the inner boundary of the outer sleeve area in the angular direction, each spiral anti-resonance structure unit is composed of spiral glass walls with the wall thickness of t, and the distance between the spiral glass walls changes along with the spiral generation direction or is kept at a specific constant. The high-order mode above a specific order is suppressed, and the suppression ratio of the high-order mode to the fundamental mode in the hollow-core optical fiber is regulated and controlled by changing the spiral type and structure parameters, so that the purpose of supporting low-loss transmission of a specific number of different-order modes is achieved. The multi-order mode low-loss transmission antenna has the characteristic of supporting multi-order mode low-loss transmission, can change a spiral line type structure and parameters according to different application scenes, is high in expansibility and feasible in preparation, and has a great application prospect in the application fields of communication, sensing, energy transmission and the like.

The invention provides a laser chip with a transverse carrier expansion superlattice and a preparation method, and relates to the technical field of semiconductor lasers. The chip sequentially comprises an N-type ohmic electrode, a substrate, a buffer layer, an N-type limiting layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, a P-type limiting layer, an ohmic contact layer and a P-type ohmic electrode. A first superlattice layer is inserted into the two sides of the P-type waveguide layer, wherein the first superlattice layer is formed by alternately overlapping an undoped and narrow-band-gap Al < x > < 7 > In < y > < 7 > Ga < 1-x > < 7-y > As layer and a P-type doped and wide-band-gap Al < x > < 8 > In < y > < 8 > Ga < 1-x > < 8-y > As layer. A second superlattice layer is inserted into the two sides of the P-type limiting layer, wherein the second superlattice layer is formed by alternately overlapping an undoped Al < x > < 10 > In < y > < 10 > Ga < 1-x > < 10-y > As layer with a narrow band gap and a P-type doped Al < x > < 11 > In < y > < 11 > Ga < 1-x > < 11-y > As layer with a wide band gap. The chip utilizes the first superlattice layer and the second superlattice layer to promote holes at two sides of a device to migrate and transport from two sides of the chip to the middle in the undoped narrow-band gap layer, large optical loss is not caused, high electro-optical conversion efficiency is ensured, the intensity of a fundamental mode is improved, and a high-order mode is inhibited.

Intensity control units 40A and 40B acquire the intensity of backscattered light when inputting signal light of two or more modes for each core in a multicore optical fiber 10, which has two or more cores and in which two or more modes propagate to each of the cores, so that the transmission direction of light differs between adjacent cores, and output a control signal for reducing the input optical power of a high-order mode other than a basic mode of the signal light by a predetermined amount so as to reduce the influence of the high-order mode on the basic mode.

The invention discloses a square optical fiber curvature sensor and a knee joint angle monitoring system, and relates to the technical field of optical fiber sensing. The square optical fiber is used for replacing a traditional optical fiber with a circular cross section, and a square optical fiber light field is distributed in a rectangular shape, so that when a rectangular light spot is subjected to mode excitation, due to uniform energy of the rectangular light spot, a large amount of light on two sides of the light spot can be excited to a high-order mode to form interference, and the sensitivity of the sensor is improved; in addition, the square optical fiber is provided with an etching cavity to form a Fabry-Perot resonant cavity, so that the sensitivity of the sensor is further improved.

To achieve high-power single transverse mode laser, we here propose a supersymmetry (SUSY)-based triple-ridge waveguide semiconductor laser structure, which is composed of an electrically pumped main broad-ridge waveguide located in the middle and a pair of lossy auxiliary partner waveguides. The auxiliary partner waveguides are designed to provide dissipative modes that can phase match and couple with the higher-order modes in the main waveguide. By appropriately manipulating the gain-loss discrimination of the modes in the laser cavity, one can effectively suppress all the undesired higher-order transverse modes while keeping the fundamental one almost unaffected, thereby ensuring stable single-mode operation with a larger emitting aperture and accordingly a higher output power than a conventional single-transverse-mode ridge waveguide diode laser.

An MCF of one embodiment combines the adoption of a plurality of cores with different refractive indices with suppression of manufacturing costs. The MCF has a glass optical fiber having a plurality of cores and a cladding, and a resin coating. The plurality of cores includes a first core with a high refractive index and a second core with a low refractive index. On a cross-section of the MCF, an arrangement of centers of a plurality of portions has no rotational symmetry about the cross-section center, the portions having a refractive index higher than that of the cladding. Furthermore, a mode leakage adjustment structure is provided to reduce a difference between a cutoff wavelength of a residual higher-order mode in the second core and a cutoff wavelength of a residual higher-order mode in the first core.

This invention discloses a system and method for achieving single-mode transmission of sapphire optical fiber using a mechanically wound helical structure, belonging to the technical field of optical fiber transmission and high-temperature optical devices. The method involves winding sapphire optical fiber along a specific pitch to form a helical structure on a core, introducing controllable bending loss to suppress higher-order modes. Subsequently, high-temperature annealing and structural fixation ensure uniform stress distribution within the fiber and maintain a stable structure. Finally, optical testing verifies the single-mode transmission effect. This method offers advantages such as simple structure, no need for complex processing equipment, low cost, and high stability, and can be widely applied in high-temperature optical fiber sensing and high-power laser transmission.

The present application discloses a terahertz single-ridge waveguide bandpass filter based on high-order modes, comprising a metal waveguide with a hollow structure, a metal ridge structure arranged in the metal waveguide, and a plurality of perturbation metal pillars, wherein the bottom of the metal ridge structure is connected to the bottom inner wall of the metal waveguide, the top of the perturbation metal pillar is connected to the top inner wall of the metal waveguide, and the bottom of the perturbation metal pillar is spaced apart from the metal ridge structure. The RWG to SRW conversion structure and the ridge structure transition section are mirror-distributed between the input port and the output port of the filter with the SRW filter structure as the center. The present application adopts air filling to reduce loss and utilizes the high-order modes of the SRW filter structure for bandpass filtering. The selection of high-order modes ensures that the filter has a good bandpass response within the target frequency band, avoiding the size and performance limitations brought by low-order modes. The perturbation metal pillars can further improve the out-of-band suppression performance of the filter.

The invention discloses an active mode demultiplexing module which comprises a mode converter, two optical circulators and a bidirectional semiconductor optical amplifier. The mode converter is used for converting a high-order mode into a fundamental mode to complete primary mode demultiplexing, fundamental mode signals after primary demultiplexing are injected into the bidirectional semiconductor optical amplifier through the two optical circulators from the positive direction and the negative direction respectively, and the signals after being shaped by the bidirectional semiconductor optical amplifier are output by the corresponding optical circulators. A bidirectional symmetrical injection structure is formed, different propagation is beneficial to separation of different signals, and mutual interference, namely mode crosstalk, between forward and reverse signals can be effectively reduced, so that a mode demultiplexing function is better completed, and an output signal has higher signal quality than a primary demultiplexing signal. Besides, by optimizing and adjusting the driving current of the bidirectional semiconductor optical amplifier or an auxiliary optical pumping mode, not only can the gain of the mode channel be dynamically adjusted, but also the power balance of the mode channel and the demultiplexing of a high extinction ratio mode can be realized; the method is especially suitable for receiving few-mode signals in a mode division multiplexing (MDM) optical transmission system and constructing optical switching nodes in a multi-dimensional multiplexing optical network.

The application provides a background noise high-order surface wave dispersion extraction method, and belongs to the technical field of seismology. The method first calculates the cross-correlation function of continuous noise data and performs preprocessing to obtain an original dispersion energy spectrum; then a reference phase shift curve between the energy of the base order and the first high-order mode is extracted; the cross-correlation function is phase-shifted based on the curve, so that the base order and the high-order surface wave are separated in time, the high-order part at the negative time is retained and inverse phase shift is performed, and a cross-correlation function containing only the high-order surface wave is obtained; then the high-order surface wave dispersion energy spectrum is obtained through frequency-Bessel transformation, and is spliced with the base order part in the original spectrum to form an enhanced dispersion energy spectrum; finally, the base order and the high-order dispersion curves are extracted after quality control. The application can effectively suppress the interference of the base order sidelobe on the high-order mode, and significantly improve the continuity and signal-to-noise ratio of the high-order surface wave dispersion energy.

This invention discloses a microwave heating device with high-order mode suppression, belonging to the field of microwave heating technology. It includes: a heater comprising a rectangular waveguide and metal ridges; the rectangular waveguide has a microwave cavity extending laterally; two metal ridges are symmetrically arranged front-to-back within the microwave cavity, with a front-to-back spacing between them, and each ridge has a material passage hole extending front-to-back; and two high-order mode suppressors, respectively located at the front and rear ends of the heater, each high-order mode suppressor having a material cavity for the workpiece to be heated to pass through, extending front-to-back and communicating with the material passage hole. This invention features a compact structure, strong electric field, rapid and uniform heating, and protection against high-frequency radiation, preventing harm to operators from microwave spatial radiation and ensuring the safe use of the microwave heating device.

This invention discloses a miniaturized, ultra-wideband, dual-polarized antenna based on non-uniform planar loading, comprising a first layer, a second layer, and a third layer arranged sequentially from top to bottom. The first layer is a non-uniform planar structure composed of four types of elements, used to improve high-frequency beam splitting. The second layer is a radiator structure consisting of two pairs of orthogonally placed magnetoelectric dipoles. The third layer is a reflector cavity composed of a planar metal reflector and a vertically loaded metal plate. This invention discloses a miniaturized, ultra-wideband, dual-polarized antenna based on non-uniform planar loading. By using the non-uniform planar structure loaded at the top of the antenna radiator, the high-frequency anti-phase currents of the electric dipole arms are modulated into in-phase currents, suppressing higher-order modes and refocusing the split beam, thereby obtaining a stable, high-gain radiation pattern throughout the entire ultra-wideband frequency range.

This invention discloses a slow-wave structure and circuit suitable for high-order modes, including a housing, an upper gate extending from the top wall to the bottom wall of the housing, and a lower gate extending from the bottom wall to the top wall of the housing. Multiple upper and lower gates are staggered, defining multiple periodic vacuum cavities. The upper and lower gates have different heights along the height direction of the slow-wave structure. An electron beam channel is formed between the upper and lower gates. This invention can suppress low-order mode competition and back-wave oscillations at low operating voltages, achieving stable operation in high-order modes and achieving high output power of 100W or more with low voltage.

The invention discloses a compact arbitrary transverse mode laser. The laser comprises a pumping source, a pumping focusing optical system, a laser total reflective mirror, a laser gain medium, a laser output mirror and an astigmatism mode converter, the pumping source emits pumping light in a gain medium absorption band; the pump light is focused and then enters the gain medium; the gain medium absorbs the pump light and generates laser gain; the total reflective mirror highly reflecting laser wavelength and the output mirror partially transmitting the laser wavelength jointly form a simple linear resonant cavity. When the laser gain medium is inclined by a preset angle relative to the optical axis of the resonant cavity, meridian light and sagittal light pass through different optical paths of the gain medium to introduce astigmatism, an HG mode facing the directions of two astigmatism symmetry axes can be reproduced, and modes facing other directions cannot be reproduced due to the astigmatism effect. Therefore, when the pump light deviates from the axis of the resonant cavity in the directions of the two astigmatic symmetry axes, any high-order HG mode with mode ordinal numbers not being zero in the two directions can be excited, and any LG mode laser can be generated through astigmatic mode conversion.

The invention relates to the technical field of semiconductor lasers, in particular to a single-mode high-power surface-emitting semiconductor laser and a manufacturing method thereof. The laser comprises an N electrode layer, an epitaxial structure, an insulating layer and a P electrode from bottom to top, wherein the epitaxial structure comprises a substrate, an N-type DBR layer, a transition layer, an active region layer, a super-symmetric coupling cavity layer, an oxide layer and a P-type DBR layer; an unoxidized hole is formed in the center of the oxide layer, a gain cavity corresponding to the unoxidized hole is formed in the super-symmetric coupling cavity layer, and a loss cavity is formed in the periphery of the gain cavity. The super-symmetric coupling cavity layer with the gain cavity and the loss cavity is arranged between the active region layer and the oxide layer, loss of an optical field in a high-order mode is limited in the loss cavity, the gain difference between a fundamental mode and the high-order mode is increased, stable single-mode output is achieved, and the output efficiency is improved. The technical problems that in a vibration exciter in the prior art, shallow layer etching on an epitaxial structure has limited high-order mode loss, and single-mode output performance and stability cannot be guaranteed are effectively solved.

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 utility model discloses a quasi single mode fiber with a large mode field effective area, which comprises a fiber core, an inner cladding, a ring core layer and an outer cladding, the fiber core is wrapped by the inner cladding, the inner cladding is wrapped by the ring core layer, the ring core layer is wrapped by the outer cladding, and the refractive index of the fiber core is larger than that of the inner cladding, the ring core layer and the outer cladding. The refractive index of the ring core layer is larger than that of the inner cladding and that of the outer cladding, and the refractive index of the inner cladding is equal to that of the outer cladding. According to the embodiment of the utility model, while the effective area of the optical fiber fundamental mode is increased, the coupling crosstalk between the fundamental mode and the high-order mode can be effectively suppressed, the communication power threshold of the optical fiber fundamental mode can be further increased on the premise of not adopting complex mode selective excitation, and the optical fiber can be widely applied to the technical field of optical communication.

The application relates to a method for generating high-order mode relativistic vortex laser based on an axial focusing pinhole plate, which comprises the following steps: preparing an axial focusing spiral pinhole plate, wherein the axial focusing spiral pinhole plate is provided with multiple pinhole groups arranged along the circumferential direction of the plate body in a regular manner, and each pinhole group comprises multiple pinholes arranged in a spiral manner; a Gaussian laser with relativistic intensity is irradiated onto the axial focusing spiral pinhole plate, and different optical paths of the laser transmitted by different pinholes to the optical axis are caused based on the pinholes on the axial focusing spiral pinhole plate, an angular phase difference is introduced into the transmitted Gaussian laser, and vortex laser is formed in a focusing area. The axial focusing spiral pinhole plate can effectively generate vortex laser, and the arrangement mode of the pinholes on the axial focusing spiral pinhole plate is adjusted to adjust the optical path difference of the transmitted laser, so that the corresponding vortex laser is generated in the focusing area, and the method is more flexible and has lower cost.

The invention relates to a plano-concave laser resonant cavity and a method for generating high-order mode laser. The plano-concave laser resonant cavity comprises a resonant cavity body, a plane mirror and a concave mirror are arranged in the resonant cavity body, a strip-shaped non-reflection area is arranged in the middle of the reflecting surface of the plane mirror or the concave mirror, and a light absorption layer is arranged on the surface of the strip-shaped non-reflection area; the plane mirror and the concave mirror are both square lenses, the long side of the strip-shaped non-reflection area is parallel to one side of the plane mirror, or the projection of the long side of the strip-shaped non-reflection area in the main optical axis direction of the concave mirror is parallel to one side of the concave mirror; the method for generating the high-order mode laser comprises the steps that the plano-concave laser resonant cavity is adopted in the laser, the width of the strip-shaped non-reflection area is changed, and the laser emits Hermite-Gaussian TEM01, TEM04 and TEM05 laser respectively; the plano-concave laser resonant cavity not only can be used for generating high-order mode laser, but also is simple in structure and low in cost, and the output function of the method for generating the high-order mode laser is strong.

The invention discloses a surface wave frequency dispersion energy spectrum imaging method, system and device for improving F-K transformation resolution based on normalization preprocessing and a medium, and belongs to the technical field of surface wave exploration, and the method comprises the steps: collecting a plurality of seismic records of an acquisition domain; performing normalization preprocessing on the selected seismic record data to obtain preprocessed surface wave data; performing two-dimensional Fourier transform to obtain domain data, and transforming a domain into a domain according to the frequency dispersion characteristic of the surface wave data; and in the phase velocity range of the surface wave, determining a frequency dispersion curve recorded by the surface wave by selecting a peak point corresponding to any frequency in a domain. According to the method, by introducing a normalization preprocessing process, the comprehensive performance of a traditional F-K transformation method in surface wave frequency dispersion energy spectrum imaging is improved, the overall resolution of a frequency dispersion energy spectrum can be enhanced, the recognition capability of high-order mode frequency dispersion energy is improved, and energy spectrum distribution of a base order and a high-order mode is clearly separated.

The present disclosure provides a semiconductor optical frequency comb laser and a preparation method, and relates to the technical field of semiconductor lasers. The semiconductor optical frequency comb laser comprises: at least one first ridge region and at least one second ridge region; in the case that the sum of the number of the first ridge regions and the number of the second ridge regions is greater than or equal to 3, the first ridge regions and the second ridge regions are alternately coupled in series; the width of each second ridge region is less than the width of each first ridge region; wherein the at least one first ridge region is used to provide gain for a light beam; the at least one second ridge region is used to suppress high-order modes in the light beam with gain; and the nonlinear effect of the gain medium is regulated by controlling the carrier concentration of the gain medium in each second ridge region to generate a frequency-modulated mode-locked optical frequency comb.

Aspects of this disclosure relate to a bulk acoustic wave having a higher order mode as a main mode. The bulk acoustic wave device includes a frame structure in a frame region and a piezoelectric layer that has an engineered region in at least part of the frame region. Related acoustic wave filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, methods of manufacture, and methods of filtering are disclosed.

This invention discloses a high-efficiency nonlinear optical frequency converter based on high-power continuous optical transmission using quartz micro / nano fiber, comprising a wavelength-tunable laser, an optical fiber amplifier, a quartz micro / nano fiber, a sealed cavity, and an optical fiber low-pass filter; the quartz micro / nano fiber includes a first untapered portion, a second untapered portion, a first tapered transition region, a second tapered transition region, and a waist region, transmitting an optical field TE. 01 The mode cutoff method precisely controls the waist diameter of micro / nano fiber and accurately tunes the input light wavelength. The nonlinear light frequency conversion process excited by high-power continuous light transmitted in quartz micro / nano fiber satisfies perfect phase matching. The fundamental mode of the input light and the higher-order mode fields of the harmonic signal light have high overlap in the waveguide mode, which can efficiently generate continuous second and third harmonic signal light. The device has high stability, high efficiency, and low cost, and can be applied in fiber lasers, all-optical signal processing, fiber optic sensing and other fields.

Provided is an elastic wave device that improves resonance characteristics in a high-order mode. The elastic wave device comprises: a piezoelectric laminate having a first main surface and a second main surface on the opposite side from the first main surface in a first direction; an electrode provided on at least one among the first main surface and the second main surface of the piezoelectric laminate; and a support member provided on the second main surface side of the piezoelectric laminate and having an acoustic reflection part on the second main surface side of the piezoelectric laminate. At least a portion of the electrode is disposed so as to overlap the acoustic reflection part in a plan view in the first direction. The piezoelectric laminate comprises: a first piezoelectric layer having the second main surface; an intermediate layer laminated on the first piezoelectric layer; and a second piezoelectric layer laminated on the intermediate layer. At least one among the material and the polarization direction of the intermediate layer is different from that of the first piezoelectric layer. At least one among the material and the polarization direction of the intermediate layer is different from that of the second piezoelectric layer.

The application discloses an integrated tunable optical attenuator based on mode-circulating phase shift and reflection, comprising a single-mode optical waveguide, a 2*2 optical coupler, a high-order mode-circulating phase shifter and a waveguide optical reflector; wherein the 2*2 optical coupler is used for splitting the optical energy of the input port into two paths and outputting the optical energy into the high-order mode-circulating phase shifter, the high-order mode-circulating phase shifter uses the high-order mode selectivity of a mode coupler and the staggered arrangement of the mode order of a mode exchanger to make the optical field circulate in the high-order mode-circulating phase shifter for multiple times, thereby achieving the fold increase of the phase modulation efficiency; the waveguide optical reflector reversely couples the optical field modulated by the high-order mode-circulating phase shifter back to the high-order mode-circulating phase shifter, so that the optical field energy and information circulate in the high-order mode-circulating phase shifter for multiple times through the multimode optical phase shift arm, thereby further doubling the optical modulation efficiency.

An object is to provide an optical fiber test method and an optical fiber test device capable of acquiring a maximum loss of a higher-order mode at a connection point of an optical fiber transmission line through which a plurality of modes propagate.The optical fiber test device according to the present invention includes: a light source unit 10 that allows probe light L1, which has a tunable wavelength and is continuous light, to enter one end T1 of an optical fiber in a fundamental mode and allows pulsed pump light L2, which is shifted to a high frequency side by a frequency at which a Brillouin interaction occurs with respect to the probe light L1, to enter the other end T2 of the optical fiber in a higher-order mode as a measurement target; and an analysis unit 20 that acquires, from a light intensity of the probe light L3 amplified by the pump light L2, a time waveform of an amplification component, calculates a connection loss of the pump light L2 at a connection point from a ratio of the amplification components before and after the connection point, acquires a wavelength dependency of the connection loss, detects a maximum value of the connection loss from the wavelength dependency of the connection loss, and sets the maximum value as a maximum loss of the higher-order mode at the connection point.