A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser

A self-seeded fiber laser incorporated with a fiber Bragg grating external cavity semiconductor laser (FBG-ECL) and a Mach-Zehnder interferometer (MZI) were reported in this paper. The MZI provided a Q-switching with response time in the order of micro-seconds. The FBG-ECL provided narrow pulses as seeds to shorten the Q-switched pulses. Experimentally, pulse width of 0.8 μs was measured, which was one fifth of the pulse width without self-seeding.     

光纤光栅对FBG-ECL静态特性的影响

光纤光栅外腔半导体激光器(FBG-ECL)在未来光通信系统占有着越来越重要的地位。根据FBG-ECL的等效腔模型,讨论了光纤光栅反射率、带宽对FBG-ECL的输出功率,阈值特性、边模抑制比等静态特性的影响。指出了存在最佳光纤光栅峰值反射率,不仅使得FBG-ECL具有更高的输出功率,而且可以获得极好的边模抑制比。最后根据实测在不同反射率下外腔激光器的激射光谱,发现理论分析结果和实验数据是吻合的。     

Slow and fast light using fiber Bragg grating F-P cavity

In this paper, we analyzed the properties of fiber Bragg grating F-P cavity with different grating parameters at two ends. The features of transmission spectra and group velocity were investigated under different parameters including slight increase for the differences of the lengths of the two gratings, the periods of the two gratings, the refractive index modulation depths of the two gratings. The characteristics of the slow light in fiber Bragg grating and fiber Bragg grating F-P cavity were also compared. The results of this study can be useful for actual experiments and applications in using the fiber Bragg grating F-P cavity in the slow light.     

The analysis of spatial light to Bragg fiber coupling ratio

On the basis of the electromagnetic field mode matching theory, the coupling efficiency ratio from spatial light to Bragg fiber is analyzed, which shows that the coupling efficiency ratio is related to the radius of focused facular, the core radius of Bragg fiber and wave number of the core. By optimizing the value of such parameters appropriately, the Bragg fiber coupling efficiency ratio can be improved. It is also important for the analysis of the coupling efficiency of Bragg fiber, which can be applied to the free optical communication system and laser radar system.     

A novel method for fabricating apodized fiber Bragg gratings

In this paper, a new implementation of the double exposure method for fabricating apodized fiber Bragg gratings by controlling the parameters of rotation stage and the number of UV-shots is presented. As a result, the average refractive index is kept nearly constant along the Bragg grating, and various apodized fiber Bragg grating with high reflectivity and high side lobe suppression ratio have been fabricated in single-mode hydrogen-loaded photosensitive fiber . The achieved side-lobe suppression ratio is larger than 25 dB.     

光纤布拉格光栅中的隙孤子存在条件

提出光纤布拉格光栅中产生隙孤子的条件和参量制约关系。利用非线性耦合模式方程建立光纤布拉格光栅中孤子的传播方程,通过扰动方法建立了参量的微分方程,计算得到参量近似解。以周期非线性光学介质中隙孤子存在的条件为依据,数学计算分析得到两组参量关系不等式。最终通过数值计算说明了这些参量之间存在制约关系和物理意义。从而理论上说明了在光纤布拉格光栅中隙孤子存在需要选择适当参量。为光纤布拉格光栅中产生隙孤子的实验和进一步的工程应用提供了理论基础。     

非线性二次曝光法制作三角形光纤Bragg光栅

提出了一种利用非线性二次曝光技术制作三角形光纤Bragg光栅的新方法.该方法只使用普通Bragg位相模板,采用两次曝光技术,通过控制光纤光栅的本地谐振波长和反射率,达到控制光纤光栅谱形的目的.第一次直接对光纤曝光,用来控制光纤光栅谐振波长;第二次通过位相模板曝光,用来控制光纤光栅的反射率.考虑到光敏光纤感光特性曲线的多项e负指数变化规律,按照"分步写入光纤光栅设计软件"进行曝光分布设计,利用"分步曝光光纤光栅写入系统"进行曝光控制,使用信息产业部第46研究所生产的DCS-01型光敏光纤,得到了线性范围1.24 nm、反射率为0～64%的三角形光纤Bragg光栅.三角形光纤Bragg光栅作为光纤光栅传感解调器件,在光纤传感领域具有重要应用价值.     

高双折射光子晶体光纤中均匀布拉格光栅的特性

研究了具有高双折射的光子晶体光纤(HB PCF)中均匀布拉格光栅(FBG)的光谱特性。利用紧凑的超格子模型,对光子晶体光纤的传输特性进行分析,研究正向传输和反向传输的模式之间的耦合规律,从而研究写入光子晶体光纤中的均匀布拉格光栅的特性。首先给出具有C6v对称性的零双折射光子晶体光纤中光纤布拉格光栅的布拉格波长λB随光纤结构参量的变化规律;然后分析一种高双折射光子晶体光纤中的光纤布拉格光栅的光谱特性,高双折射使两个不同偏振态的反射峰分开较大;最后分析了一种常用的双模双折射光子晶体光纤中光纤布拉格光栅的光谱特性,LP01模和LPe11模的两个偏振态对应的反射谱都由于高双折射而分开。     

半导体激光器与光纤光栅对接耦合研究

半导体激光器管芯与光纤光栅的对接耦合对光纤光栅外腔激光器的特性起到关键作用。利用散射矩阵分析了激光器管芯与光纤光栅外腔的对接耦合，发现对接的距离以及对接的耦合效率决定了光纤光栅外腔激光器的性能。在强反馈情况下,激射波长在光纤光栅外腔有效反射率决定的布喇格波长内随对接耦合距离周期性的变化,对弱反馈情况则有些不同。同时对比了两种情况的边模抑制比。该分析为实际制作器件提供了指导。     

Influence of uniaxial crystal material cladding on reflectivity and dispersion of uniform fiber Bragg grating

The fiber Bragg grating with cladding made of uniaxial crystal material whose optical axis is parallel to the axis of fiber Bragg grating proposed in the paper published in 2003 was investigated again and an error was corrected in the calculation, its effective index, reflectivity and dispersion were examined using coupled-mode theory and numeric solution. The calculated results indicate that no low frequency cutoff phenomenon exists in the HE₁₁ mode, more power is transmitted by the core of the fiber with cladding made of isotropic material, the reflectivity of the fiber Bragg grating with cladding made of uniaxial crystal material is much higher than that with cladding made of isotropic material, the parameter K_cl, i.e., the ratio of the extraordinary to the ordinary ray refractive index, has a stronger impact on the reflectivity, Bragg wavelength and the dispersion of this kind of fiber Bragg grating when it varied from 1.00 to 1.01 than in other regions. This means that the characteristics of the fiber Bragg grating with uniaxial crystal cladding can be changed through adjusting K_cl while keeping its length, periodicity and the other parameters as constants.     

切趾技术对光纤布拉格光栅法布里-珀罗滤波器反射特性优化的研究

利用矩阵分析法,针对两个相同光栅构成的光纤布拉格光栅法布里-珀罗(F-P)腔滤波器进行理论分析。数值模拟分析了光栅长度变化对光栅以及F-P腔滤波器反射特性的影响,指出光栅长度增加对反射特性影响的优缺点,分析利用常用切趾函数对光栅进行切趾,减小由于光栅长度增加导致反射谱的的旁瓣增大,对组成的F-P腔滤波器的反射特性的优化,得到了光栅切趾对F-P腔滤波器的反射特性的影响规律。对于在实际应用中制作出性能优良的光纤布拉格光栅F-P腔滤波器有一定的参考价值。     

Arbitrary chirped fiber Bragg gratings on application of filtering for optical communications

This paper presents an analysis of how to obtain narrow transmission band in the centre of the spectrum of the arbitrary chirped fiber Bragg grating (ACFBG). Grating chirp coefficient and refractive index profile are the critical parameters in contributing to performance of fiber Bragg grating. The reflection spectra and transmission band were analyzed with different refractive index profile. Apodization techniques are used to get optimized reflection spectra. The simulations are based on solving coupled mode equations by transfer matrix method that describes the interaction of guided modes.     

三角形大带宽反射光谱光纤光栅的设计和制备

反射谱具有三角形形状的光纤光栅在光纤传感等领域中具有重要的应用前景。利用遗传算法设计出了产生三角形光谱分布的光纤光栅的耦合系数沿光纤的分布。计算表明,三角形光谱光纤光栅是可以实现的,其反射带宽可以通过光栅的啁啾量进行调节,常周期的三角光栅反射带宽小,变周期的三角光栅反射带宽大,其带宽同其啁啾量大致相等。实验中,采用光束扫描法制备了反射底宽为0．77nm三角形光谱的光纤光栅。     

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.     

极窄带宽的布拉格光纤光栅光谱特性研究

根据理想模展开下的耦合模方程，对光纤布拉格光栅的峰值反射率公式进行了数学推导，得到了布拉格光纤光栅的光谱反射率表达式。全面讨论了光栅周期、光纤栅长、光致折射率微扰最大值等参数与光纤光栅反射光谱的关系。仿真结果显示了固定参数下布拉格光栅的极限窄带宽，得到的反射率为1、带宽为0.02nm的窄带宽布拉格光栅，比现今分布式传感系统中使用的布拉格光栅的带宽窄1个数量级。这种布拉格光纤光栅用于分布式传感系统，可大大提高分布式传感系统中光源的带宽利用率，消除各信号间的相互串扰，提高传感光栅复用数目，降低解调系统成本。     

激光多普勒测速精度分析

激光多普勒测速（ＬａｓｅｒＤｏｐｐｌｅｒＶｅｌｏｃｉｍｅｔｒｙ）以其高精度、使用方便而在速度测试领域得到广泛的应用。人们也因此而忽视了对影响其测试精度的因素进行系统的分析。为此,本文主要对影响激光多普勒测速精度的因素作了具体分析。主要分析了有限渡越时间、测控体中的示踪粒子、光电探测器、激光束定位等因素,并提出了在具体实验时的注意事项。     

基于叠栅的Bragg光纤光栅综合方法的研究

提出一种新的光纤光栅综合方法，将Bragg光纤光栅的层剥离综合算法与光纤叠栅理论结合起来，层剥离综合算法根据需要的反射谱计算出光纤光栅的折射率分布，用多个带切趾函数的光纤叠栅来拟合这个折射率分布，通过改变各叠栅中的相关参数，可以得到适合需要的反射谱，相对误差一般小于4.0%。该方法具有简单、快速、易于实现的特点。     

低损耗大模面积W型布喇格光纤

通过有限元法建立模型,讨论了布喇格光纤设计参量对光子带隙的影响,发现当增加掺锗玻璃环的厚度或折射率时,会使带隙移向长波.通过在紧邻纤芯处施加一层掺氟低折射率玻璃,设计了一种大模面积W型布喇格光纤.计算表明:W型布喇格光纤可以有效减小限制损耗,提高光纤的抗弯曲能力.本文设计的布喇格光纤的纤芯直径为30 μm,在波长1.06 μm限制损耗约为0.1 dB/km,且维持单一横模传输.     

光纤布拉格光栅中隙孤子的EPP方法分析

提出了利用EPP方法分析光纤布拉格光栅中隙孤子的解。基于非线性耦合模式方程(NLCME)定性地分析了无微扰条件下的隙孤子参数与孤子的其它特性的关系。利用EPP方法分析了隙孤子的能量特性。证明了隙孤子的速度影响形态特性和能量分布。从理论上解释了已观察到的一系列隙孤子的试验现象,对光纤布拉格光栅中产生隙孤子的应用具有理论意义。     

Modal phase-matching second harmonic generation in Bragg fiber

Modal phase-matching second harmonic generation in uniformly poled Bragg fiber is theoretically proposed. The very low group velocity of the modes in Bragg fiber near the in-band cutoff frequencies leads to high nonlinear conversion efficiency comparable to that of the periodically poled conversional fiber. The subsequence phase-matched bandwidth reduction by slow light can be retrieved in a certain degree through structure parameters optimization.