Minimization of losses and calculation of the optical properties of Bragg fiber waveguides with a hollow core

A numerical method for solving the inverse problem of determining the geometry of the multilayer shell of a Bragg waveguide that has the lowest waveguide losses for a given mode has been developed with the use of the genetic algorithm. For the calculated designs of waveguides, the distribution of the coordinates of the boundaries of shell layers has been found to be aperiodic under the condition r ₁ ≤ λ due to the axial symmetry of the problem. Waveguide losses for the TE ₀₁, TM ₀₁, and HE ₁₁ modes satisfy the conditions \(\alpha _{TM_{01} } > \alpha _{HE_{11} } > \alpha _{TE_{01} } \). It follows from the dependence of n _eff obtained for these modes on the core radius and number of shell layers that any change in the structure of the waveguide leads to the violation of the optimal propagation regime for these modes. A Bragg fiber waveguide with a hollow core that is designed for the TE ₀₁ mode and directs light in the single-mode regime is presented. The main fraction of losses in this waveguide is attributed to material absorption.     

宽带空芯THz单模单偏振光纤

传统的THz单模单偏振光纤大部分都是基于实芯光纤设计的,增加了THz波的传输损耗。最近几年,也有一些关于空芯THz单模单偏振光纤的报道。但是,他们的带宽太窄,往往只能在单一频率附近工作,影响了单偏振器件在THz范围内的使用价值和技术优势。为了解决这些问题,设计了一种新颖结构的空芯THz单模单偏振器件。它拥有超过0.1 THz的带宽,工作频率范围从1.63 THz到1.73 THz。这种器件对于THz通信网络的建设和应用具有重要意义。     

Optical fiber modulator derivates from hollow optical fiber with suspended core

A fiber optic integrated modulation-depth-tunable modulator based on a type of hollow optical fiber with suspended core is proposed and investigated. We synthesized magnetic fluid containing superparamagnetic Fe(3)O(4) nanoparticles and encapsulated it in the hollow optical fiber as the cladding layer of the suspended core by fusing the hollow optical fiber with the multimode optical fibers. The light with a wavelength of 632.8 nm is coupled in and out of the modulating element by a tapering technique. Experimental results show that the light attenuation in the system can be greatly influenced by only 2.0×10(-2) μL of the magnetic fluid under different magnetic field strengths. The saturated modulation depth is 43% when the magnetic field strength is 489 Oe. The response time of the system is <120 ms. Significantly, this work presents information for the development of all-fiber modulators, including other integrated electro-optic devices, such as optical switch, optical fiber filter, and magnetic sensors utilizing the special structure of this hollow optical fiber with suspended core and superparamagnetic magnetic fluid.     

Motion characteristics of Bragg grating solitons in rectangle-apodized fiber Bragg gratings

We introduce both concave and convex rectangular apodizations in the middle of fiber Bragg gratings to achieve slow light. Based on the nonlinear coupled mode equations (NLCMEs), the transmission characteristics of grating solitons in rectangle-apodized gratings are numerically simulated and analyzed. The rectangular apodization can change the grating coupling coefficient to give rise to slow and capture the solitons in gratings. The effects of the soliton energy parameters, the width of rectangular apodization and the variation of the coupling coefficient on the soliton transmission are presented. The results show that, the velocity of solitons can be slowed down, and the capability to capture a soliton depends on the energy of input solitons, coupling coefficient, and the rectangular width. Two kinds of soliton capture methods are proposed and compared with each other.     

Study of non-linear properties of hollow core photonic crystal fiber

A highly non-linear hollow core photonic crystal fiber (PCF) having three ring-hexagonal structure is designed. The full vector finite element method with perfectly matched layer is used to investigate the non-linear properties of hollow core PCF effectively. The effective area of modal pattern is also studied for the same newly designed structure. It is found that when effective area is very small the non-linearity is very high.     

Research on the air core Bragg fiber with defect state

A new method based on the Transfer Matrix Theory of Bragg fiber to research a Bragg fiber with defect state has been developed in this paper. The distribution of the electromagnetic field in the Bragg fiber is analyzed, and the loss and efficiency of the Bragg fiber are also estimated based on optical power confinement factor Γ. Thereby, the influence of the defect for transmitting characteristics in Bragg fiber has been researched.     

谐振式光子带隙光纤陀螺一体化方案

实现了使用光子带隙光纤的一体化谐振式光纤陀螺方案,设计并制作了谐振腔中基于微光学结构的耦合器。实验测得制作的谐振腔清晰度为3.7。搭建了基于该谐振腔的陀螺系统,并对其主、次偏振态的谐振曲线进行了实际测量。实验结果测得该系统60 s零漂为2.45 ()/s,及1 h长期稳定性为7.11 ()/s。同时,实现了对应陀螺输出50 ()/s（积分时间10 s）及100 ()/s（积分时间10 s）的模拟转速实验,验证了该陀螺系统的Sagnac效应。分析得到耦合损耗是影响该陀螺系统性能的主要因素。验证了该谐振腔结构具有应用于陀螺系统的可行性,为谐振式光纤陀螺性能进一步提高提供了参考。     

谐振式光子带隙光纤陀螺一体化方案

实现了使用光子带隙光纤的一体化谐振式光纤陀螺方案,设计并制作了谐振腔中基于微光学结构的耦合器。实验测得制作的谐振腔清晰度为3.7。搭建了基于该谐振腔的陀螺系统,并对其主、次偏振态的谐振曲线进行了实际测量。实验结果测得该系统60 s零漂为2.45 ()/s,及1 h长期稳定性为7.11 ()/s。同时,实现了对应陀螺输出50 ()/s（积分时间10 s）及100 ()/s（积分时间10 s）的模拟转速实验,验证了该陀螺系统的Sagnac效应。分析得到耦合损耗是影响该陀螺系统性能的主要因素。验证了该谐振腔结构具有应用于陀螺系统的可行性,为谐振式光纤陀螺性能进一步提高提供了参考。     

耐高温光纤Bragg光栅的响应特性研究

以耐高温光纤光栅和普通的光纤光栅为实验研究对象,研究了其高温特性。普通的FBG，当温度超过300℃以上，光纤光栅已变黑变脆，虽然有传感特性，但已不能在实际中应用；通过对耐高温光栅裸栅进行300℃以上的高温实验，发现耐高温FBG处于20℃～350℃之间时反射波长与温度之间有着良好的线性关系，且光栅性能良好，没有出现被碳化现象，灵敏度为0.01nm/MPa；随着温度进一步升高，FBG反射波长与温度开始呈现非线性关系。实验结果表明，耐高温光栅适合于高温油气井下应用。     

光纤光栅在干式空心电抗器固化中的测温研究

采用埋入式光纤Bragg光栅温度传感器,实现了对干式空心电抗器固化过程中各包封层的温度监测。在制作过程中,将温度传感器埋在干式空心电抗器导线外包封表面,连接光纤从电抗器上沿引出。电抗器绕线与包封完成后放入干燥室内固化,监测电抗器各包封层在固化过程中的温度变化。通过监测得到了电抗器各包封温度变化的曲线图,当炉温示值稳定在140℃时,各包封温度低于预期,分布在105~125℃之间,且由外向内逐渐降低。通过对干式空心电抗器固化过程中的温度进行监测,可实时了解并改进干燥固化过程中出现的问题,对保证电抗器的质量及安全具有重要意义。     

Raman perturbation and surface core soliton in hollow photonic crystal fiber

Effect of Raman scattering and higher order dispersion are investigated in case of surface core or gap solitons, known to exist in hollow core photonic crystal fibers. The necessary conditions for the existence of the soliton are analyzed in the parameter plane. It is observed that these conditions are compatible with the famous Vakhitov-Kolokolov (VK) criterion. In the later part the system of partial differential equations are solved by ETDRK method from which the shapes of the pulses are investigated as it travels along the z direction. Both the terms, intrapulse Raman scattering and higher order dispersion have important effect on the propagation characteristics     

均匀光纤Bragg光栅局部横向受力特性研究

对均匀光纤Bragg光栅(FBG)局部横向受力特性进行了理论和实验研究.采用传输矩阵法分析了FBG其中一段横向受力时的反射光谱变化,并且建立了相应的数学模型.研究表明,当FBG局部横向受力时,受压长度对反射光谱无影响,反射光谱分裂点的波长与横向作用力呈线性正比关系并具有周期性,分裂点反射率与受力位置的关系为近似双曲正切关系. 关键词： 光纤Bragg光栅 传输矩阵法 局部横向受力 分裂点     

大模场啁啾光纤光栅的光谱特性

 将一种矩阵算法拓展应用于数值求解多模耦合模微分方程, 并使用该矩阵算法对大模场啁啾光纤光栅的光谱特性进行了理论研究。结果表明, 大模场多模光纤光栅因模式的自耦合和互耦合而使反射谱存在多个反射峰, 这与单模光纤光栅的反射谱不同。由于光栅周期存在啁啾, 大模场光纤光栅的反射峰分裂, 且峰值反射率减小。使用高斯切趾函数可使反射峰分裂在一定程度上得到改善。     

光纤布拉格光栅非线性传输特性的数值研究

 回顾了光纤布拉格光栅非线性耦合模方程的数值求解方法,分析了基于隐式龙格 库塔方法的预报校正系统的特点。为实现简捷、高效、高阶精度的光纤布拉格光栅非线性耦合模方程的数值仿真,设计了基于连分式修正法的预报-校正系统并与基本方法进行了对比。采用该方法可以极大地加长光栅的分段长度以节约计算时间,同时也不存在仿真过程中因计算方法产生的不收敛现象,误差对比分析表明该方法能够准确地模拟光栅的非线性传输特性。为解决静态和动态情况下仿真方法不统一并避免数值计算引起的冲击响应,根据光栅中光波传输的物理过程建立了静态和动态情况下统一的数值仿真模型并研究了仿真中所采用的多种技术,利用这些技术能够有效地仿真连续波和脉冲输入情况下光纤布拉格光栅的非线性传输特性。     

大模场啁啾光纤光栅的光谱特性

将一种矩阵算法拓展应用于数值求解多模耦合模微分方程, 并使用该矩阵算法对大模场啁啾光纤光栅的光谱特性进行了理论研究。结果表明, 大模场多模光纤光栅因模式的自耦合和互耦合而使反射谱存在多个反射峰, 这与单模光纤光栅的反射谱不同。由于光栅周期存在啁啾, 大模场光纤光栅的反射峰分裂, 且峰值反射率减小。使用高斯切趾函数可使反射峰分裂在一定程度上得到改善。     

高能激光辐照下光纤布拉格光栅响应特性

为探索光纤布拉格光栅在高能激光参数测量方面的应用,通过实验和数值模拟研究分析了其在高能激光辐照下的响应特性。通过解传热方程,获得了光纤布拉格光栅在高能激光辐照下的热响应特性。利用一个光纤光栅解调仪,记录了光纤布拉格光栅在高能激光辐照下的波长漂移现象。实验结果表明：在一定的功率密度范围内,光纤布拉格光栅的最大波长漂移与其所受的辐照功率密度成线性关系,该结果与理论模拟相符。     

Thermal characteristics analysis of an IGBT using a fiber Bragg grating

This paper proposes a new method to develop a thermal model of an insulated gate bipolar transistor (IGBT) employing an optical fiber sensor mounted on the chip structure. Some features of the sensor such as electromagnetic immunity, small size and fast response time, allow the identification of temperature changes generated by the energy loss during device operation through direct measurement. In fact, this measurement method is considered impossible with conventional sensors. The online monitoring of the junction temperature enables identify the thermal characteristics of the IGBT. The results are used to develop an accurate model to simulate the heat generated during the device conduction and switching processes. The model showed a difference of only 0.3% between the measured and simulated results, besides allowing evaluate separately the heat generated by each turn-ON/OFF process.     

Efficient way for detection of alcohols using hollow core photonic crystal fiber sensor

Optical Review - In this study, a simple hollow core hexagonal structured photonic crystal fiber is offered and analyzed to discern commonly used different type of alcohols in our daily life. The...     

Energetic few-cycle pulse compression in gas-filled hollow core fiber with concentric phase mask

The compression of high-energy, linearly polarized pulses in a gas-filled hollow core fiber(HCF) by using a concentric phase mask is studied theoretically. Simulation results indicate that using a properly designed concentric phase mask, a40-fs input pulse centered at 800 nm with energy up to 10.0 mJ can be compressed to a full width at half maximum(FWHM) of less than 5 fs after propagating through a neon-filled HCF with a length of 1 m and diameter of 500 μm with a transmission efficiency of 67%, which is significantly higher than that without a concentric phase mask. Pulses with energy up to 20.0 mJ can also be efficiently compressed to less than 10 fs with the concentric phase mask. The higher efficiency due to the concentric phase mask can be attributed to the redistribution of the transverse intensity profile, which reduces the effect of ionization. The proposed method exhibits great potential for generating few-cycle laser pulse sources with high energy by the HCF compressor.     

单点相移光纤光栅光谱特性的研究与应用

可调谐窄线宽掺铒光纤激光器具有线宽窄、噪声低等优点,在光纤通信、光纤传感、相干探测和合成等方面有广泛的应用。根据传输矩阵法, 利用Matlab软件仿真出单点相移光纤光栅的透射谱,通过对不同相移量、不同相移点位置、不同光栅的长度以及不同纤芯有效折射率的单点相移光纤光栅透射谱进行分析,得到了影响其相移峰的透射率、线宽、位置的主要因素,并提出了一种利用相移量为π且相移点在中点的相移光纤光栅作为滤波窗口的可调谐窄线宽掺铒光纤激光器的方案。