A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The em...A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The emissions of the laser diode bar are coupled into multimode fiber array.The radi ation from individual ones of emitter regions is optically coupled into individu al ones of fiber array.Total coupling efficiency and fiber output power are 75% and 15W,respectively.展开更多
The output radiation from the 100μm×1μm aperture of a high power Laser Diode (LD) is efficiently coupled into a 50μm multimode optical fiber.The fiber output of the high power LD with high brightness and high ...The output radiation from the 100μm×1μm aperture of a high power Laser Diode (LD) is efficiently coupled into a 50μm multimode optical fiber.The fiber output of the high power LD with high brightness and high power density is achieved.The power density is up to 3 6×104W/cm2 and the coupling efficiency is 70%.The extreme divergence and the astigmatism of high power LDs require the optics with complex lens structures and high performance.A double-curved lens with two crossed cylindrical lenses structured on both sides of the glass substrate is used in the coupling system.展开更多
Coupling plane wave into a single-mode fiber （SMF） with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fibe...Coupling plane wave into a single-mode fiber （SMF） with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler （AFC） which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent （SPGD） algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80/3tad. The compensation bandwidth is 35 Hz at sine-jitter of 15 ~rad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error （MSE） of coupling efficiency drops from 7.43% to 1.75%.展开更多
The theoretical investigation of the coupling efficiency of a laser diode to a single mode fiber via a hemispherical lens on the tip of the tapered fiber in the presence of possible transverse offset and angular misma...The theoretical investigation of the coupling efficiency of a laser diode to a single mode fiber via a hemispherical lens on the tip of the tapered fiber in the presence of possible transverse offset and angular mismatch is reported.Without the misalignment,coupling efficiency increases with the decreasing of taper length.With the misalignment,this relation is that the coupling efficiency decreases with each kind of offset.展开更多
Nano-silica treated with different kinds of coupling agent （KH550, A-143, A-151） was used to modify the surface condition of glass fiber, and then, the modified glass fiber/unsaturated polyester resin （UPR） compos...Nano-silica treated with different kinds of coupling agent （KH550, A-143, A-151） was used to modify the surface condition of glass fiber, and then, the modified glass fiber/unsaturated polyester resin （UPR） composites materials were prepared. Scanning electron microscopy （SEM）, dynamic mechanical analysis （DMA）, and impact test were used to characterize the composite materials＇ structure and properties. The morphology of composite materials shows that the adhesion between nano-silica and glass fiber is improved when silane coupling agent is added in. The DMA and impact test results show that silane coupling agent （especially KH550 and A-151） could effectively improve the composite＇s mechanical properties. When the dose of KH550 was 0.1% （m ： m）, the storage modulus and impact strength reached the maximum.展开更多
A type of As2S3 chalcogenide glass mid-infrared dual-core photonic crystal fiber has been proposed. The dualcore photonic crystal fiber （PCF） consists of two asymmetric cores. The high polarization property and the ...A type of As2S3 chalcogenide glass mid-infrared dual-core photonic crystal fiber has been proposed. The dualcore photonic crystal fiber （PCF） consists of two asymmetric cores. The high polarization property and the coupling characteristics have been studied by using the finite dement method and mode coupling theory. Numerical results show that the birefringence at wavelength λ = 10 μm is up to 0.01386 and the coupling length can reach wavelength = 5 μm, 261 μm and 271.44 μm for x-polarized mode and y-polarized mode, respectively. It demonstrates that a 6.786-ram-long fiber can exhibit an extinction ratio of better than -10 dB and a bandwidth of 180 nm.展开更多
Excess loss on the short wavelength side of the Bragg resonant wavelength caused by cladding mode coupling limits wide use of grating in the fiber communication system, especially in densed wavelength division multipl...Excess loss on the short wavelength side of the Bragg resonant wavelength caused by cladding mode coupling limits wide use of grating in the fiber communication system, especially in densed wavelength division multiplexing (DWDM) system. A novel photosensitive fiber design that have depressed cladding and photosensitive inner cladding in the same fiber is proposed, which can suppress cladding mode coupling greatly. Using MCVD method B/Ge codoped fiber with depressed cladding was fabriceted out, which was also doped in boron and germanium and had the photosensitivity. Finally, the transmission spectrum of written grating in this fiber by phase mask method verified its larger photosensitivity and greatly suppression of cladding mode coupling.展开更多
Multimode fiber has a richer spatial dimension than single-mode fiber,and is an ideal platform for studying many novel nonlinear effects.We established a strong linear coupling and short-range fiber model to understan...Multimode fiber has a richer spatial dimension than single-mode fiber,and is an ideal platform for studying many novel nonlinear effects.We established a strong linear coupling and short-range fiber model to understand the interactive effects of linear coupling and nonlinear effects.We find that strong linear coupling can compensate for the group delay between eigenmodes and cause energy fluctuation between modes which weakens the nonlinear effects.In high energy pulses,the interaction of linear coupling and nonlinear effects can help producing weak dispersion waves when the spectrum is broadened.Since linear coupling in a mode group is common and unavoidable,these results may provide a certain theoretical explanation for multi-mode nonlinear phenomena.展开更多
The beams of 980nm high-power LDs are analyzed, and the reasons that aspect ratio of LD beams is high are explained. It is certified by the test that cylindrical lens can efficiently compress the perpendicular diverge...The beams of 980nm high-power LDs are analyzed, and the reasons that aspect ratio of LD beams is high are explained. It is certified by the test that cylindrical lens can efficiently compress the perpendicular divergence angle of the beam. Some typical and popular lensed fibers were compared and analyzed according to coupling characteristics. The factors which affect the coupling efficiency and tolerance of the wedged-shaped GRIN tipped lensed fiber are pointed out, and some methods to reduce the coupling loss of the lensed fibers are proposed finally.展开更多
<div style="text-align:justify;"> Currently, coupled mode theory (CMT) is widely used for calculating the coupling coefficient of twin-core fibers (TCFs) that are used in a broad range of important app...<div style="text-align:justify;"> Currently, coupled mode theory (CMT) is widely used for calculating the coupling coefficient of twin-core fibers (TCFs) that are used in a broad range of important applications. This approach is highly accurate for scenarios with weak coupling between the cores but shows significant errors in the strong coupling scenarios, necessitating the use of a more accurate method for coupling coefficient calculations. Therefore, in this work, we calculate the coupling coefficients of TCFs using the supermode theory with finite element method (FEM) that has higher accuracy than CMT, particularly for the strong coupling TCF. To investigate the origin of the differences between the results obtained by these two methods, the modal field distributions of the supermodes of TCF are simulated and analyzed in detail. </div>展开更多
An optic-fiber sensor system for measuring distributed forces is presented. The sensor system chooses high-birefringent fiber as sensing e-iement. Based on coupling effects of polarization modes in high-birefringent ...An optic-fiber sensor system for measuring distributed forces is presented. The sensor system chooses high-birefringent fiber as sensing e-iement. Based on coupling effects of polarization modes in high-birefringent fiber, the distribution of the force points along the sensing fiber can be measured by detecting mode couplings in the fiber which are caused by external force disturbance. The location and magnitude of the measured forces are determined by a heterodyne interferometry and the technique of optic path scanning. The spatial resolution of the sensor system is better than 0. 15m for a 50m testing fiber.展开更多
We propose a novel kind of wavelength-selective coupling for the terahertz range based on solid five-core fiber （FCF）. The performances of coupling, propagation characteristics, and confinement loss properties are n...We propose a novel kind of wavelength-selective coupling for the terahertz range based on solid five-core fiber （FCF）. The performances of coupling, propagation characteristics, and confinement loss properties are numerically investigated by using a full vector beam propagation method （BPM）. Simulation results show that it is possible to realize a broad- band wavelength-selective coupling. The coupling length can reach 1.913 cm, and the confinement loss is better than 1.965 ×10^-4 cm^-1. Furthermore, a parameter, the power difference, is defined, and it numerically demonstrates the working performance of the wavelength-selective coupler; that is, when the power difference is better than - 15 dB, the frequency located in the range of 0.76 THz-100 THz is separated relatively well from the frequency of 0.3 THz. Finally, the effect of the structural parameter on the working performance of the coupler is also investigated. We show that the performance optimization is possible by appropriately tuning the core diameter, and the tunabilities of frequency and bandwidth are possible by appropriately tuning the pitch. The wavelength-selective coupler is of potential application for optical fiber sensing and communication in terahertz wavelength division multiplexer fields.展开更多
In this paper,a theoretical model to analyze the mode coupling induced by heat,when the fiber amplifier works at high power configuration,is proposed.The model mainly takes into consideration the mode field change due...In this paper,a theoretical model to analyze the mode coupling induced by heat,when the fiber amplifier works at high power configuration,is proposed.The model mainly takes into consideration the mode field change due to the thermally induced refractive index change and the coupling between modes.A method to predict the largest average output power of fiber is also proposed according to the mode coupling theory.The largest average output power of a large pitch fiber with a core diameter of 190 μm and an available pulse energy of 100 mJ is predicted to be 540 W,which is the highest in large mode field fibers.展开更多
For the superstructure fiber grating （SFG） consisting of fiber Bragg grating （FBG） and long-period fiber grating （LPFG）, there exist three kinds of coupling： the contra-directional coupling between forward prop...For the superstructure fiber grating （SFG） consisting of fiber Bragg grating （FBG） and long-period fiber grating （LPFG）, there exist three kinds of coupling： the contra-directional coupling between forward propagating core mode and backward propagating core mode, the contra-directional coupling between core mode and cladding mode, and the co-directional coupling between core mode and cladding mode. By using the similarity transformation method for the coupled mode equations, the effects of three coupling coefficients κcoL, κclL, and κsL on the transmission and re- flection spectra of SFG have been investigated. The simulations show that the overall intensity of the transmission spectrum of SFG is decided by LPFG, that the main lobes of the transmission and reflectivity spectra of SFG are decided by coupling coefficients κcoL and κsL, and that the side lobes of the transmission and reflectivity spectra are decided by coupling coefficients κclL and κsL.展开更多
Based on the index-induced mode coupling between the higher-order mode in core and the fundamental mode in cladding tubes,the single-mode operation can be realized in any antiresonant fibers(ARFs)when satisfying that ...Based on the index-induced mode coupling between the higher-order mode in core and the fundamental mode in cladding tubes,the single-mode operation can be realized in any antiresonant fibers(ARFs)when satisfying that the area ratio of cladding tube and core is about 0.46:1,and this area ratio also should be modified according to the shape and the number of cladding tubes.In the ARF with nodal core boundary,the mode in core also can couple with the mode in the wall of core boundary,which can further enhance the suppression of high-order mode.Accordingly,an ARF with conjoint semi-elliptical cladding tubes realizes a loss of higher-order mode larger than 30 dB/m;simultaneously,a loss of fundamental mode loss less than 0.4 dB/m.展开更多
According to the principle of choosing the light source in the fiber optic sensing measurement,semiconductor laser is used as the light source of fiber optic sensor and single-mode fiber is used as the tail fiber of l...According to the principle of choosing the light source in the fiber optic sensing measurement,semiconductor laser is used as the light source of fiber optic sensor and single-mode fiber is used as the tail fiber of light source. Based on optical design software Zemax’s pure non-sequential components,a coupling system of semiconductor laser and single-mode fiber is designed. By analyzing the beam characteristics of the semiconductor laser and the coupled mode theory of semiconductor laser and single-mode fiber,the combined lens consists of a ball lens and a collimating lens for the purpose of improving the coupling efficiency and adjusting tolerance. The simulation results show that the coupling efficiency can reach about 78% by using one million ray traces on non-sequential components,while the experimental test result is 69.11%,accordingly,the reasons for the difference between the experiment and the simulation results are analyzed.展开更多
The catalytic oxidative cou pling of methane(OCM)to C_(2) hydrocarbons(C_(2)H_(6) and C_(2)H_(4))represents one of the most effective ways to convert natural gas to more useful products,which can be performed effectiv...The catalytic oxidative cou pling of methane(OCM)to C_(2) hydrocarbons(C_(2)H_(6) and C_(2)H_(4))represents one of the most effective ways to convert natural gas to more useful products,which can be performed effectively using La_(0.6)Sr0.4Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)perovskite hollow fiber membrane microreactor.In this work,the effects of adding a thin BaCe_(0.8)Gd_(0.2)O_(3-δ)(BCG)catalyst film onto the inner LSCF fiber surface as the OCM catalyst and a porous Ba0.5Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)perovskite layer onto the outer LSCF surface to improve the oxygen permeation were evaluated.Between 700℃and 1000℃,methane conversion increased in the order of uncoated,BCG and BSCF-coated,and BCG-coated LSCF hollow fiber while Coselectivity and C_(2)-yield increased in the order of BCG and BSCF-coated,uncoated,and BCG-coated LSCF hollow fiber.Oxygen permeation flux at the same temperature range,on the other hand,was enhanced in the order of uncoated,BCG-coated,and BCG and BSCF-coated LSCF hollow fiber.This finding demonstrates the complex interplay between oxygen permeation and OCM performance.The BCG and BSCFcoated hollow fiber was also subjected to thermal cycles between 850℃and 900℃for up to 175 hours during which the fiber showed minor degradation in oxygen permeation fluxes and relatively stable OCM performance.展开更多
Gradient-index rod lens (GRIN-lens) whose pitch is ordinary value with bevel ferrule coupling system is analyzed, an equivalent method which can be used to analyze this system is put forward, and a general formula for...Gradient-index rod lens (GRIN-lens) whose pitch is ordinary value with bevel ferrule coupling system is analyzed, an equivalent method which can be used to analyze this system is put forward, and a general formula for determining the coupling loss with axes mismatch, radial mismatch, and angular mismatch is derived by use of the Gaussian field approximation and mode-field coupling theory. The experimental results are in good agreement with the theory prediction. It indicates that these formulas are suitable to analyze the gradient-index rod lens coupling system with pigtail fiber.展开更多
The purpose of this study is to investigate the effect of the concentration of silane coupling solution on the tensile strength of basalt fiber and the interfacial properties of basalt fiber reinforced polymer composi...The purpose of this study is to investigate the effect of the concentration of silane coupling solution on the tensile strength of basalt fiber and the interfacial properties of basalt fiber reinforced polymer composites.The surface treatment of basalt fibers was carried out using an aqueous alcohol solution method.Basalt fibers were subjected to surface treatment with 3-Methacryloxypropyl trimethoxy silane at 0.5 wt.%,1 wt.%,2 wt.%,4 wt.%and 10 wt.%.The basalt monofilament tensile tests were carried out to investigate the variation in strength with the concentration of the silane coupling agent.The microdroplet test was performed to examine the effect of the concentration of the silane coupling agent on interfacial strength of basalt reinforced polymer composites.The film was formed on the surface of the basalt fiber treated silane coupling agent solution.The tensile strength of basalt fiber increased because the damaged fiber surface was repaired by the firm of silane coupling agent.The firm was effective in not only the surface protection of basalt fiber but also the improvement on the interfacial strength of fiber-matrix interface.However,the surface treatment using the high concentration silane coupling agent solution has an adverse effect on the mechanical properties of the composite materials,because of causing the degradation of the interfacial strength of the composite materials.展开更多
We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of sin...We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of single-mode fibers(SMFs).Firstly,the two sections of MMFs were spliced with two sections of SMFs.Then,the MMFs were fused to two ends of FMF to form a symmetrically structured fiber-optic MZI structure.In this structure,the MMF served as the optical mode field coupling element,and the cladding and core of the FMF are the interference arm and the reference arm of the MZI structure,respectively.We investigated the sensor's response characteristics of the temperature and strain.The experimental results indicate that the sensor is sensitive to temperature variation,and the temperature response sensitivity is up to 61.4 pm/℃ in the range of 40-250℃,while the sensor has weak strain sensitivity,its strain sensitivity is only-0.72 pm/μe in the strain range of 0-1400μe.Moreover,the sensor has good stability and repeatability.In brief,the proposed fiber optic high temperature sensor has good properties,such as high sensitivity,compact structure,good stability and repeatability,which can be used for monitoring the temperature of submerged oil electric pump units under oil wells.展开更多
文摘A piece of multimode optical fiber with a low num er ical aperture (NA) is used as an inexpensive microlens to collimate the output r adiation of a laser diode bar in the high numerical aperture (NA) direction.The emissions of the laser diode bar are coupled into multimode fiber array.The radi ation from individual ones of emitter regions is optically coupled into individu al ones of fiber array.Total coupling efficiency and fiber output power are 75% and 15W,respectively.
文摘The output radiation from the 100μm×1μm aperture of a high power Laser Diode (LD) is efficiently coupled into a 50μm multimode optical fiber.The fiber output of the high power LD with high brightness and high power density is achieved.The power density is up to 3 6×104W/cm2 and the coupling efficiency is 70%.The extreme divergence and the astigmatism of high power LDs require the optics with complex lens structures and high performance.A double-curved lens with two crossed cylindrical lenses structured on both sides of the glass substrate is used in the coupling system.
基金Project supported by the National Natural Science Foundation of China （Grant No. 61205069）.
文摘Coupling plane wave into a single-mode fiber （SMF） with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler （AFC） which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent （SPGD） algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80/3tad. The compensation bandwidth is 35 Hz at sine-jitter of 15 ~rad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error （MSE） of coupling efficiency drops from 7.43% to 1.75%.
文摘The theoretical investigation of the coupling efficiency of a laser diode to a single mode fiber via a hemispherical lens on the tip of the tapered fiber in the presence of possible transverse offset and angular mismatch is reported.Without the misalignment,coupling efficiency increases with the decreasing of taper length.With the misalignment,this relation is that the coupling efficiency decreases with each kind of offset.
基金Supported by the National Natural Science Foundation of of China(J1210061)
文摘Nano-silica treated with different kinds of coupling agent （KH550, A-143, A-151） was used to modify the surface condition of glass fiber, and then, the modified glass fiber/unsaturated polyester resin （UPR） composites materials were prepared. Scanning electron microscopy （SEM）, dynamic mechanical analysis （DMA）, and impact test were used to characterize the composite materials＇ structure and properties. The morphology of composite materials shows that the adhesion between nano-silica and glass fiber is improved when silane coupling agent is added in. The DMA and impact test results show that silane coupling agent （especially KH550 and A-151） could effectively improve the composite＇s mechanical properties. When the dose of KH550 was 0.1% （m ： m）, the storage modulus and impact strength reached the maximum.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10874145)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091333110010)+1 种基金the Natural Science Foundation of Hebei Province, China (Grant No. F2009000481)the China Postdoctoral Science Foundation (Grant Nos. 20080440014 and 200902046)
文摘A type of As2S3 chalcogenide glass mid-infrared dual-core photonic crystal fiber has been proposed. The dualcore photonic crystal fiber （PCF） consists of two asymmetric cores. The high polarization property and the coupling characteristics have been studied by using the finite dement method and mode coupling theory. Numerical results show that the birefringence at wavelength λ = 10 μm is up to 0.01386 and the coupling length can reach wavelength = 5 μm, 261 μm and 271.44 μm for x-polarized mode and y-polarized mode, respectively. It demonstrates that a 6.786-ram-long fiber can exhibit an extinction ratio of better than -10 dB and a bandwidth of 180 nm.
文摘Excess loss on the short wavelength side of the Bragg resonant wavelength caused by cladding mode coupling limits wide use of grating in the fiber communication system, especially in densed wavelength division multiplexing (DWDM) system. A novel photosensitive fiber design that have depressed cladding and photosensitive inner cladding in the same fiber is proposed, which can suppress cladding mode coupling greatly. Using MCVD method B/Ge codoped fiber with depressed cladding was fabriceted out, which was also doped in boron and germanium and had the photosensitivity. Finally, the transmission spectrum of written grating in this fiber by phase mask method verified its larger photosensitivity and greatly suppression of cladding mode coupling.
基金This work has been supported by the National Key Research and Development Program of China(No.2018YFB0504400)the National Natural Science Foundation of China(Nos.61775107,61322510 and 11674177)the Tianjin Natural Science Foundation(No.19JCZDJC31200).
文摘Multimode fiber has a richer spatial dimension than single-mode fiber,and is an ideal platform for studying many novel nonlinear effects.We established a strong linear coupling and short-range fiber model to understand the interactive effects of linear coupling and nonlinear effects.We find that strong linear coupling can compensate for the group delay between eigenmodes and cause energy fluctuation between modes which weakens the nonlinear effects.In high energy pulses,the interaction of linear coupling and nonlinear effects can help producing weak dispersion waves when the spectrum is broadened.Since linear coupling in a mode group is common and unavoidable,these results may provide a certain theoretical explanation for multi-mode nonlinear phenomena.
文摘The beams of 980nm high-power LDs are analyzed, and the reasons that aspect ratio of LD beams is high are explained. It is certified by the test that cylindrical lens can efficiently compress the perpendicular divergence angle of the beam. Some typical and popular lensed fibers were compared and analyzed according to coupling characteristics. The factors which affect the coupling efficiency and tolerance of the wedged-shaped GRIN tipped lensed fiber are pointed out, and some methods to reduce the coupling loss of the lensed fibers are proposed finally.
文摘<div style="text-align:justify;"> Currently, coupled mode theory (CMT) is widely used for calculating the coupling coefficient of twin-core fibers (TCFs) that are used in a broad range of important applications. This approach is highly accurate for scenarios with weak coupling between the cores but shows significant errors in the strong coupling scenarios, necessitating the use of a more accurate method for coupling coefficient calculations. Therefore, in this work, we calculate the coupling coefficients of TCFs using the supermode theory with finite element method (FEM) that has higher accuracy than CMT, particularly for the strong coupling TCF. To investigate the origin of the differences between the results obtained by these two methods, the modal field distributions of the supermodes of TCF are simulated and analyzed in detail. </div>
文摘An optic-fiber sensor system for measuring distributed forces is presented. The sensor system chooses high-birefringent fiber as sensing e-iement. Based on coupling effects of polarization modes in high-birefringent fiber, the distribution of the force points along the sensing fiber can be measured by detecting mode couplings in the fiber which are caused by external force disturbance. The location and magnitude of the measured forces are determined by a heterodyne interferometry and the technique of optic path scanning. The spatial resolution of the sensor system is better than 0. 15m for a 50m testing fiber.
基金Project supported by the Specific Scientific and Technological Cooperation between China and Russia(Grant No.2010DFR80140)the National Natural Science Foundation of China(Grant No.51309059)
文摘We propose a novel kind of wavelength-selective coupling for the terahertz range based on solid five-core fiber （FCF）. The performances of coupling, propagation characteristics, and confinement loss properties are numerically investigated by using a full vector beam propagation method （BPM）. Simulation results show that it is possible to realize a broad- band wavelength-selective coupling. The coupling length can reach 1.913 cm, and the confinement loss is better than 1.965 ×10^-4 cm^-1. Furthermore, a parameter, the power difference, is defined, and it numerically demonstrates the working performance of the wavelength-selective coupler; that is, when the power difference is better than - 15 dB, the frequency located in the range of 0.76 THz-100 THz is separated relatively well from the frequency of 0.3 THz. Finally, the effect of the structural parameter on the working performance of the coupler is also investigated. We show that the performance optimization is possible by appropriately tuning the core diameter, and the tunabilities of frequency and bandwidth are possible by appropriately tuning the pitch. The wavelength-selective coupler is of potential application for optical fiber sensing and communication in terahertz wavelength division multiplexer fields.
基金supported by the National Natural Science Foundation of China(Grant No.61475081)
文摘In this paper,a theoretical model to analyze the mode coupling induced by heat,when the fiber amplifier works at high power configuration,is proposed.The model mainly takes into consideration the mode field change due to the thermally induced refractive index change and the coupling between modes.A method to predict the largest average output power of fiber is also proposed according to the mode coupling theory.The largest average output power of a large pitch fiber with a core diameter of 190 μm and an available pulse energy of 100 mJ is predicted to be 540 W,which is the highest in large mode field fibers.
基金Supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China (708064)Natural Science Foundation of Wuhan University of Technology (471-38650024)
文摘For the superstructure fiber grating （SFG） consisting of fiber Bragg grating （FBG） and long-period fiber grating （LPFG）, there exist three kinds of coupling： the contra-directional coupling between forward propagating core mode and backward propagating core mode, the contra-directional coupling between core mode and cladding mode, and the co-directional coupling between core mode and cladding mode. By using the similarity transformation method for the coupled mode equations, the effects of three coupling coefficients κcoL, κclL, and κsL on the transmission and re- flection spectra of SFG have been investigated. The simulations show that the overall intensity of the transmission spectrum of SFG is decided by LPFG, that the main lobes of the transmission and reflectivity spectra of SFG are decided by coupling coefficients κcoL and κsL, and that the side lobes of the transmission and reflectivity spectra are decided by coupling coefficients κclL and κsL.
基金Project supported by the National Natural Science Foundation of China(Grant No.62075159)the National Key Research and Development Program of China(Grant No.2017YFF0104603)+1 种基金the 111 Project of China(Grant No.B17031)the Major Scientific and Technological Innovation Projects of Key Research and Development Plans in Shandong Province,CHina(Grant No.2019JZZY020206)。
文摘Based on the index-induced mode coupling between the higher-order mode in core and the fundamental mode in cladding tubes,the single-mode operation can be realized in any antiresonant fibers(ARFs)when satisfying that the area ratio of cladding tube and core is about 0.46:1,and this area ratio also should be modified according to the shape and the number of cladding tubes.In the ARF with nodal core boundary,the mode in core also can couple with the mode in the wall of core boundary,which can further enhance the suppression of high-order mode.Accordingly,an ARF with conjoint semi-elliptical cladding tubes realizes a loss of higher-order mode larger than 30 dB/m;simultaneously,a loss of fundamental mode loss less than 0.4 dB/m.
基金Youth Science and Technology Research Foundation of Shanxi Province(No.2015021104)Programs for Science and Technology Development of Shanxi Province(No.201703D121028-2)
文摘According to the principle of choosing the light source in the fiber optic sensing measurement,semiconductor laser is used as the light source of fiber optic sensor and single-mode fiber is used as the tail fiber of light source. Based on optical design software Zemax’s pure non-sequential components,a coupling system of semiconductor laser and single-mode fiber is designed. By analyzing the beam characteristics of the semiconductor laser and the coupled mode theory of semiconductor laser and single-mode fiber,the combined lens consists of a ball lens and a collimating lens for the purpose of improving the coupling efficiency and adjusting tolerance. The simulation results show that the coupling efficiency can reach about 78% by using one million ray traces on non-sequential components,while the experimental test result is 69.11%,accordingly,the reasons for the difference between the experiment and the simulation results are analyzed.
基金the research funding provided by the National Natural Science Foundation of China(21805206,22179073).
文摘The catalytic oxidative cou pling of methane(OCM)to C_(2) hydrocarbons(C_(2)H_(6) and C_(2)H_(4))represents one of the most effective ways to convert natural gas to more useful products,which can be performed effectively using La_(0.6)Sr0.4Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)perovskite hollow fiber membrane microreactor.In this work,the effects of adding a thin BaCe_(0.8)Gd_(0.2)O_(3-δ)(BCG)catalyst film onto the inner LSCF fiber surface as the OCM catalyst and a porous Ba0.5Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)perovskite layer onto the outer LSCF surface to improve the oxygen permeation were evaluated.Between 700℃and 1000℃,methane conversion increased in the order of uncoated,BCG and BSCF-coated,and BCG-coated LSCF hollow fiber while Coselectivity and C_(2)-yield increased in the order of BCG and BSCF-coated,uncoated,and BCG-coated LSCF hollow fiber.Oxygen permeation flux at the same temperature range,on the other hand,was enhanced in the order of uncoated,BCG-coated,and BCG and BSCF-coated LSCF hollow fiber.This finding demonstrates the complex interplay between oxygen permeation and OCM performance.The BCG and BSCFcoated hollow fiber was also subjected to thermal cycles between 850℃and 900℃for up to 175 hours during which the fiber showed minor degradation in oxygen permeation fluxes and relatively stable OCM performance.
文摘Gradient-index rod lens (GRIN-lens) whose pitch is ordinary value with bevel ferrule coupling system is analyzed, an equivalent method which can be used to analyze this system is put forward, and a general formula for determining the coupling loss with axes mismatch, radial mismatch, and angular mismatch is derived by use of the Gaussian field approximation and mode-field coupling theory. The experimental results are in good agreement with the theory prediction. It indicates that these formulas are suitable to analyze the gradient-index rod lens coupling system with pigtail fiber.
文摘The purpose of this study is to investigate the effect of the concentration of silane coupling solution on the tensile strength of basalt fiber and the interfacial properties of basalt fiber reinforced polymer composites.The surface treatment of basalt fibers was carried out using an aqueous alcohol solution method.Basalt fibers were subjected to surface treatment with 3-Methacryloxypropyl trimethoxy silane at 0.5 wt.%,1 wt.%,2 wt.%,4 wt.%and 10 wt.%.The basalt monofilament tensile tests were carried out to investigate the variation in strength with the concentration of the silane coupling agent.The microdroplet test was performed to examine the effect of the concentration of the silane coupling agent on interfacial strength of basalt reinforced polymer composites.The film was formed on the surface of the basalt fiber treated silane coupling agent solution.The tensile strength of basalt fiber increased because the damaged fiber surface was repaired by the firm of silane coupling agent.The firm was effective in not only the surface protection of basalt fiber but also the improvement on the interfacial strength of fiber-matrix interface.However,the surface treatment using the high concentration silane coupling agent solution has an adverse effect on the mechanical properties of the composite materials,because of causing the degradation of the interfacial strength of the composite materials.
基金supported by the Scientific Research Program Funded by Shaanxi Provincial Education Department (No.15JK1573)the Postgraduate Innovation and Practice Ability Development Fund of Xi’an Shiyou University (No.YCS21211084)。
文摘We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of single-mode fibers(SMFs).Firstly,the two sections of MMFs were spliced with two sections of SMFs.Then,the MMFs were fused to two ends of FMF to form a symmetrically structured fiber-optic MZI structure.In this structure,the MMF served as the optical mode field coupling element,and the cladding and core of the FMF are the interference arm and the reference arm of the MZI structure,respectively.We investigated the sensor's response characteristics of the temperature and strain.The experimental results indicate that the sensor is sensitive to temperature variation,and the temperature response sensitivity is up to 61.4 pm/℃ in the range of 40-250℃,while the sensor has weak strain sensitivity,its strain sensitivity is only-0.72 pm/μe in the strain range of 0-1400μe.Moreover,the sensor has good stability and repeatability.In brief,the proposed fiber optic high temperature sensor has good properties,such as high sensitivity,compact structure,good stability and repeatability,which can be used for monitoring the temperature of submerged oil electric pump units under oil wells.
