This paper presents an investigation of specific optical fiber core mode leakage behavior that occurs in high-power double-clad fiber lasers as a result of thermally-induced refractive index variations. A model of the...This paper presents an investigation of specific optical fiber core mode leakage behavior that occurs in high-power double-clad fiber lasers as a result of thermally-induced refractive index variations. A model of the power transfer between the core modes and the cladding modes during thermally-induced refractive index variations is established based on the mode coupling theory. The results of numerical simulations based on actual laser parameters are presented. Experimental measurements were also carried out, the results showed good agreement with the corresponding simulation results.展开更多
Decreasing mode coupling coefficient(κ) is an effective approach to suppress the inter-core crosstalk. Therefore, we deploy a low index rod and rectangle trench in the middle of two neighboring cores to reduce κ so ...Decreasing mode coupling coefficient(κ) is an effective approach to suppress the inter-core crosstalk. Therefore, we deploy a low index rod and rectangle trench in the middle of two neighboring cores to reduce κ so that the overlap of electric field distribution can be suppressed. We also propose approximate analytical solution(AAS) for κ of two crosstalk suppression models, which are two cores with one low index rod deployed in the middle and two cores with one low index rectangle trench deployed in the middle. We then do some modification for the results obtained by AAS and the modified results are proved to agree well with that obtained by finite element method(FEM). Therefore, we can use the modified AAS to get inter-core crosstalk for abovementioned two models quickly.展开更多
In this paper, the influencing factors that affect few-mode and multi core optical fiber channel are analyzed in a comprehensive way. The theoretical modeling and computer simulation of the information channel are car...In this paper, the influencing factors that affect few-mode and multi core optical fiber channel are analyzed in a comprehensive way. The theoretical modeling and computer simulation of the information channel are carried out and then the modeling scheme of few-mode multicore optical fiber channel based on non-uniform mode field distribution is put forward. The proposed modeling scheme can not only exponentially increases the system capacity through fewmode multi-core optical fiber channel, but has better transmission performance compared to the channel of the same type to the uniform channel revealing from the simulation results.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
A novel fiber strain sensor is proposed, based on the two-mode interference of a suspended-core fiber. A fullvectorial finite difference mode solver is employed as the numerical tool for characterizing the proposed st...A novel fiber strain sensor is proposed, based on the two-mode interference of a suspended-core fiber. A fullvectorial finite difference mode solver is employed as the numerical tool for characterizing the proposed strain sensor. The numerical results show that the proposed strain sensor has an estimated sensitivity of 0.05 rad/（m-με）, higher than that of the strain sensors using conventional multimode fibers, while the temperature sensitivity of the proposed sensor is relatively low.展开更多
Kinds of photonic crystal fibers with chalcogenide core tellurite cladding composite microstructure are proposed. The multi-core photonic crystal fiber can reach the higher nonlinearity coefficient and the larger effe...Kinds of photonic crystal fibers with chalcogenide core tellurite cladding composite microstructure are proposed. The multi-core photonic crystal fiber can reach the higher nonlinearity coefficient and the larger effective mode area. The small single-core photonic crystal fiber has a very high nonlinearity coefficient. At the wavelength λ=0.8μm, the nonlinearity coefficient can reach 31.37053 W-1·m-1, at the wavelength λ=1.55μm, the nonlinearity coefficient is 11.19686W-1·m-1.展开更多
With linearly coupled nonlinear Schrodinger equations,numerical analysis has been performed on the mode locking forming procedure of a fiber laser in the linear cavity configuration.The fiber is Yb-doped multi-core ph...With linearly coupled nonlinear Schrodinger equations,numerical analysis has been performed on the mode locking forming procedure of a fiber laser in the linear cavity configuration.The fiber is Yb-doped multi-core photonic crystal fiber and semiconductor saturable absorber mirror(SESAM) is adopted as the nonlinear transmission element to start mode locking.Because of the noise randomness,initial pulse would be picked out by SESAM in one or more cores which makes the multi-core mode locking quite different from single-core one.The two situations are compared and fully discussed.Mode locking in multi-core photonic crystal fiber laser can be realized only if the couple coefficient between the cores and the temporal overlap between the pulses in different cores are large enough.展开更多
By means of the weakly guiding approximation, the mode spot sizes Wx and Wy of the fundamental mode along the semimajor （x-direction） and semiminor （y-direction） axes of the fiber core in elliptical core two- mode...By means of the weakly guiding approximation, the mode spot sizes Wx and Wy of the fundamental mode along the semimajor （x-direction） and semiminor （y-direction） axes of the fiber core in elliptical core two- mode fiber are discussed. The variation of their ratio value Wx/W9 with the operation wavelength A and the length ratio a/b between the semimajor axis and the semiminor axis of the fiber core is analyzed. Based on this analysis, the distribution figures of two-lobe interferential mode patterns are evaluated and simulated quantitatively for different phase difference changes between LP01 and LP~~n modes. The two-lobe interferential mode patterns have the same profile and distribute symmetrically when the phase difference equals ~r/2. Their central distance S becomes larger when W~：/W~ augments gradually. F^rthermore, the equation about the central distance S of the two-lobe interferential mode patterns is given when the operation wavelength varies between 0.65 and 1.31 #m, which is important to applications shuch as sensors and coupling devices between different fibers.展开更多
Core mode cutoff is a useful concept not only for a tapered single-core fiber(SCF) but also for a tapered multicore fiber(MCF) to realize cladding mode transmission. In this paper, cut-off conditions of either core mo...Core mode cutoff is a useful concept not only for a tapered single-core fiber(SCF) but also for a tapered multicore fiber(MCF) to realize cladding mode transmission. In this paper, cut-off conditions of either core mode for tapered SCFs or supermodes for MCFs are theoretically investigated. Rigorous analytical formulas are derived for the modes of SCF by a three-layer waveguide model, and an approximation formula of the cut-off condition is given for the LP01 mode. The supermodes of MCFs are analyzed by the coupling mode theory, and the cut-off condition is calculated by a numerical method. Simulation results show that the in-phase supermode of MCFs has a similar cut-off condition with that of SCF. Based on this property, a convenient approximate formula is given to estimate the cut-off condition of the in-phase supermode for tapered MCFs.展开更多
Stimulated Raman scattering (SRS) transmission modes in highly elliptical-core optical fiber of three different structures are experimentally researched.The measuring setup,SRS spectrum and photographs of Stokes modes...Stimulated Raman scattering (SRS) transmission modes in highly elliptical-core optical fiber of three different structures are experimentally researched.The measuring setup,SRS spectrum and photographs of Stokes modes are given.The observed phenomena are completely different from those on circular-core graded-index optical fiber.The beam sizes of SRS remain constant and SRS light transmits with the characteristics of higher-order.mode.In addition,the experimental results are theoretically explained with fiber-optical dispersion theory and SRS phase matching conditions.Experimental results and theoretical analyses are in good agreement.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61307057 and 61675114)
文摘This paper presents an investigation of specific optical fiber core mode leakage behavior that occurs in high-power double-clad fiber lasers as a result of thermally-induced refractive index variations. A model of the power transfer between the core modes and the cladding modes during thermally-induced refractive index variations is established based on the mode coupling theory. The results of numerical simulations based on actual laser parameters are presented. Experimental measurements were also carried out, the results showed good agreement with the corresponding simulation results.
基金supported by National B a-sic Research Program of China(Grant No.2012CB315905)National Natural Science Foundation of China(Grant No.61501027)+1 种基金China Postdoctoral Science Foundation(Grant No.2015M570934)Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-15-031A1)
文摘Decreasing mode coupling coefficient(κ) is an effective approach to suppress the inter-core crosstalk. Therefore, we deploy a low index rod and rectangle trench in the middle of two neighboring cores to reduce κ so that the overlap of electric field distribution can be suppressed. We also propose approximate analytical solution(AAS) for κ of two crosstalk suppression models, which are two cores with one low index rod deployed in the middle and two cores with one low index rectangle trench deployed in the middle. We then do some modification for the results obtained by AAS and the modified results are proved to agree well with that obtained by finite element method(FEM). Therefore, we can use the modified AAS to get inter-core crosstalk for abovementioned two models quickly.
基金supports from National High Technology 863 Program of China(No.2013AA013403,2015AA015501,2015AA015502,2015AA015504)National NSFC(No.61425022/61522501/61307086/61475024/61275158/61201151/61275074/61372109)+4 种基金Beijing Nova Program(No.Z141101001814048)Beijing Excellent Ph.D.Thesis Guidance Foundation(No.20121001302)the Universities Ph.D.Special Research Funds(No.20120005110003/20120005120007)Fund of State Key Laboratory of IPOC(BUPT)P.R.China
文摘In this paper, the influencing factors that affect few-mode and multi core optical fiber channel are analyzed in a comprehensive way. The theoretical modeling and computer simulation of the information channel are carried out and then the modeling scheme of few-mode multicore optical fiber channel based on non-uniform mode field distribution is put forward. The proposed modeling scheme can not only exponentially increases the system capacity through fewmode multi-core optical fiber channel, but has better transmission performance compared to the channel of the same type to the uniform channel revealing from the simulation results.
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>
基金Project supported by the Shanghai Leading Academic Discipline Project (Grant No.S30108)
文摘A novel fiber strain sensor is proposed, based on the two-mode interference of a suspended-core fiber. A fullvectorial finite difference mode solver is employed as the numerical tool for characterizing the proposed strain sensor. The numerical results show that the proposed strain sensor has an estimated sensitivity of 0.05 rad/（m-με）, higher than that of the strain sensors using conventional multimode fibers, while the temperature sensitivity of the proposed sensor is relatively low.
基金the National Natural Science Foundation of China(Grant Nos.61178026 and 60978028)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20091333110010)the Natural Science Foundation of Hebei Province,China(Grant No.E2012203035)
文摘Kinds of photonic crystal fibers with chalcogenide core tellurite cladding composite microstructure are proposed. The multi-core photonic crystal fiber can reach the higher nonlinearity coefficient and the larger effective mode area. The small single-core photonic crystal fiber has a very high nonlinearity coefficient. At the wavelength λ=0.8μm, the nonlinearity coefficient can reach 31.37053 W-1·m-1, at the wavelength λ=1.55μm, the nonlinearity coefficient is 11.19686W-1·m-1.
基金supported by National Basic Research Program of China (2006CB806002 and 2010CB327604)the National Natural Science Foundation of China (60838004 and 60978022)+2 种基金the Key Project of Chi-nese Ministry of Education (108032)the Foundation for the Author of National Excellent Doctoral Dissertation of China (2007B34)the Program for New Century Excellent Talents in University (NCET-07-0597)
文摘With linearly coupled nonlinear Schrodinger equations,numerical analysis has been performed on the mode locking forming procedure of a fiber laser in the linear cavity configuration.The fiber is Yb-doped multi-core photonic crystal fiber and semiconductor saturable absorber mirror(SESAM) is adopted as the nonlinear transmission element to start mode locking.Because of the noise randomness,initial pulse would be picked out by SESAM in one or more cores which makes the multi-core mode locking quite different from single-core one.The two situations are compared and fully discussed.Mode locking in multi-core photonic crystal fiber laser can be realized only if the couple coefficient between the cores and the temporal overlap between the pulses in different cores are large enough.
基金National Basic Research Program of China under Grant No.2006CB806001.
文摘By means of the weakly guiding approximation, the mode spot sizes Wx and Wy of the fundamental mode along the semimajor （x-direction） and semiminor （y-direction） axes of the fiber core in elliptical core two- mode fiber are discussed. The variation of their ratio value Wx/W9 with the operation wavelength A and the length ratio a/b between the semimajor axis and the semiminor axis of the fiber core is analyzed. Based on this analysis, the distribution figures of two-lobe interferential mode patterns are evaluated and simulated quantitatively for different phase difference changes between LP01 and LP~~n modes. The two-lobe interferential mode patterns have the same profile and distribute symmetrically when the phase difference equals ~r/2. Their central distance S becomes larger when W~：/W~ augments gradually. F^rthermore, the equation about the central distance S of the two-lobe interferential mode patterns is given when the operation wavelength varies between 0.65 and 1.31 #m, which is important to applications shuch as sensors and coupling devices between different fibers.
文摘Core mode cutoff is a useful concept not only for a tapered single-core fiber(SCF) but also for a tapered multicore fiber(MCF) to realize cladding mode transmission. In this paper, cut-off conditions of either core mode for tapered SCFs or supermodes for MCFs are theoretically investigated. Rigorous analytical formulas are derived for the modes of SCF by a three-layer waveguide model, and an approximation formula of the cut-off condition is given for the LP01 mode. The supermodes of MCFs are analyzed by the coupling mode theory, and the cut-off condition is calculated by a numerical method. Simulation results show that the in-phase supermode of MCFs has a similar cut-off condition with that of SCF. Based on this property, a convenient approximate formula is given to estimate the cut-off condition of the in-phase supermode for tapered MCFs.
文摘Stimulated Raman scattering (SRS) transmission modes in highly elliptical-core optical fiber of three different structures are experimentally researched.The measuring setup,SRS spectrum and photographs of Stokes modes are given.The observed phenomena are completely different from those on circular-core graded-index optical fiber.The beam sizes of SRS remain constant and SRS light transmits with the characteristics of higher-order.mode.In addition,the experimental results are theoretically explained with fiber-optical dispersion theory and SRS phase matching conditions.Experimental results and theoretical analyses are in good agreement.
