Simulation model of magneto-optic fiber Bragg gratings and its applications in Sagnac interferometers

According to the symmetry of transmission matrix for non-uniform magneto-optic fiber Bragg gratings (MFBGs),the simulation model of the non-uniform MFBGs with bidirectional injection of light has been presented for the Optisystem software.The simulation model is verified by comparing with the Matlab numeric results using the piecewise-uniform MFBG model.As an example,the polarization-dependent loss (PDL) of an MFBG-based Sagnac interferometer (MSI) is analyzed in detail.Simulation results indicate that the magnetic field sensitivity of the MSI system can be improved by optimizing the coupling coefficient of the coupler,and the maximum of peak PDL is up to three times that of the single MFBG structure.The simulation model proposed in the paper is useful for the design of MFBG-based optical information devices.     

磁光光纤Bragg光栅中偏振消光比特性分析

通过分析磁光光纤Bragg光栅中偏振消光比特性,提出一种利用峰值偏振消光比测量磁场的新方案。利用OptiSystem软件仿真表明,当光栅耦合系数远大于磁光耦合参量时,峰值偏振消光比与外加磁场的对数值成线性关系,与理论分析结果一致。文章还给出了峰值消光比与光栅长度、折射率调制深度和费尔德常数之间关系的解析式,可方便地用于分析磁场的测量性能。     

光纤相位光栅（布喇格光栅）的制作

讨论了光纤的光敏性，并着重综述了光纤相位光栅（布喇格光栅）的制作方法。     

Magneto-optic field coupling in optical fiber Bragg gratings

A magnetic sensor utilizing direct magneto-optic field coupling in an optical fiber Bragg grating (FBG) is experimentally demonstrated. The FBG’s cladding is etched to expose the propagating evanescent light to the fiber’s surroundings. The etched FBG is surrounded with iron oxide nanoparticles and placed in a magnetic field perpendicular to the fiber. Measurements demonstrate that the λ_B shifts nonlinearly as a function of magnetic field, i.e. comparable to the magnetization versus magnetic field behavior of the nanoparticles measured by a SQUID magnetometer. This direct manipulation of light with magnetic fields provides an approach to develop future sensors relying on electromagnetic interactions.     

Thermal tuning of polymer optical fiber Bragg gratings

Bragg gratings in polymethyl methacrylate (PMMA)-based polymer fibers were created and were tuned thermally. It is found that the tuning range is more than 18 nm over a temperature variation of 50°C. More importantly, no hysteresis effect was observed as the gratings were heated up and cooled down     

Nonlinear switching of optical pulses in fiber Bragg gratings

We study numerically the nonlinear switching characteristics of optical pulses transmitted though fiber Bragg gratings. We consider both the uniform and phase-shifted gratings and compare their performance as a nonlinear switch. The nonlinear coupled-mode equations were solved numerically to obtain the pulse-switching characteristics. The steady-state behavior known to occur for continuous-wave optical beams is realized only for pulses wider than 10 ns with long tails. For pulsewidths in the range 0.1-1 ns, the use of phase-shifted gratings reduces the switching threshold, but the on-off contrast is generally better for uniform gratings. We also quantify the effects of rise and fall times associated with an optical pulse on nonlinear switching by considering the Gaussian pulses with smooth tails and nearly rectangular pulses with sharp leading and trailing edges.     

光纤布拉格光栅在光脉冲压缩中的应用

光纤布拉格光栅(FBG)由于其独特的光学特性和灵活的设计特点,在光通信系统中有着广泛的应用,包括光脉冲压缩、全光开关、全光复用/解复用器、色散补偿器和光存储等等.文章主要对FBG在光脉冲压缩中的应用进行了分析,并对几种压缩器的结构、原理和性能作了介绍.     

FBG的衍射光学特性和耦合模理论分析

从衍射光学的角度出发研究了光纤布喇格光栅（ Ｆ Ｂ Ｇ） 的光学特性,进而采用理想模展开的耦合模理论对光纤布喇格光栅的模场分布进行了详细分析,推导出反射率、布喇格反射波长及反射主峰带宽等特性参数的表达式。计算结果表明,理论与实验结果吻合较好,从而验证了理论结果的正确性     

Reconfigurable multichannel optical add-drop multiplexersincorporating eight-port optical circulators and fiber Bragg gratings

We propose and demonstrate two new strictly nonblocking reconfigurable multichannel optical add-drop multiplexers (RM-OADMs) using optical circulators and fiber Bragg gratings. By effectively using eight-port optical circulators, the new structures significantly reduce component count and insertion loss, and achieve good crosstalk performance. One of the new RM-OADMs potentially achieves the lowest insertion loss among existing RM-OADMs     

Rapidly reconfigurable optical phase encoder-decoders based on fiber Bragg gratings

We demonstrate the capacity for fast dynamic reconfiguration of optical code-division multiple access (OCDMA) phase en/decoders based on fiber Bragg gratings and a thermal phase-tuning technique. The tuning time between two different phase codes is measured to be less than 2 s. An OCDMA system using tunable-phase decoders is compared with a system using fixed-phase decoders and, although the system using fixed-phase decoders exhibits a shorter output autocorrelation pulsewidth and lower sidelobes, the system using tunable-phase decoders has advantages of flexibility and a more relaxed requirement on the input pulsewidth.     

A novel technique for optical dense comb filters using sampled fiber Bragg gratings

The optical dense comb filters are indispensable components for dense wavelength multiplexing systems. In this paper, a novel and basic method is proposed to realize optical dense comb filters. The reflection spectrum of sampled fiber Bragg grating is analyzed after applying a phase shifting technique that varies the phase of the grating. The spectral densification and shifting effects of periodic phase shifts are investigated and it is shown that desired amount of channel multiplying can be provided by using appropriate value of densification factor. Moreover, a quantization technique is proposed in order to reduce the phase shifting series which complicated by the increase of densification factor.     

Long-phase error-free fiber Bragg gratings

Stitching errors in the phase mask degrade the spectral response of fiber Bragg gratings fabricated with the phase mask technique. We successfully fabricated a stitching error-free phase mask and applied it to the fabrication of fiber Bragg gratings (FBGs). The gratings have no observable excess sidelobes in the reflectivity and show excellent wavelength selectivity     

Dispersion compensation of fiber Bragg gratings in 3100 km high speed optical fiber transmission system

By optimizing the fabrication process of the chirped optical fiber Bragg grating (CFBG), some key problems of CFBG are solved, such as fabrication repetition, temperature stability, group delay ripple (GDR), fluctuation of the reflection spectrum, polarization mode dispersion (PMD), interaction of cascaded CFBG, and so on. The CFBG we fabricated can attain a temperature coefficient less than 0.0005 nm/℃, and the smoothed GDR and the fluctuation of the reflection spectrum are smaller than 10ps and 0.5dB, respec-tively. The PMD of each CFBG is less than 1 ps and the dispersion of each grating is larger than -2600 ps/(nm·km). With dispersion compensated by the CFBGs we fabricated, a 13×10 Gbit/s 3100 km ultra long G.652 fiber transmission system is successfully imple-mented without electric regenerator. The bit error rate (BER) of the system is below 10-4 without forward error correction (FEC); when FEC is added, the BER is below 10-12. The power penalty of the carrier-suppressed return-to-zero (CSRZ) code transmission system is only 2.5 dB.     

光孤子在高斯变迹光栅中传输特性的数值分析

为了研究光纤光栅中布喇格孤子的传输特性,基于耦合波理论采用有限差分法在孤子传播速度与传输距离无关的条件下,数值模拟了布喇格孤子在高斯变迹光纤光栅中的传输以及孤子之间的相互作用,得到一些有意义的结果.结果表明,输入功率和初始脉宽等初始条件的不同将导致孤子峰值强度的周期变化;具有初始频率啁啾时布喇格孤子在传输过程中被展宽(正啁啾)或被窄化(负啁啾),并始终受到高斯变迹光栅的制约.当输入两个孤子时,它们之间的相互作用对其相对相位和相对振幅参量敏感.     

Lightwave applications of fiber Bragg gratings

Fiber Bragg gratings (FBGs) have emerged as important components in a variety of lightwave applications. Their unique filtering properties and versatility as in-fiber devices is illustrated by their use in wavelength-stabilized lasers, fiber lasers, remotely pump amplifiers. Raman amplifiers, phase conjugators, wavelength converters, passive optical networks, wavelength division multiplexers (WDMs) demultiplexers, add/drop multiplexers, dispersion compensators, and gain equalizers     

光纤布喇格光栅的制作技术

简单介绍了光纤布喇格光栅（ Ｆ Ｂ Ｇ） 的原理及光学特性,详细阐述了 Ｆ Ｂ Ｇ 的制作技术。此外,详细地描述了采用 Ｋｒ Ｆ 激光器,利用位相掩模法光刻光纤形成 Ｆ Ｂ Ｇ 的实验。此种方法与其他方法相比,有很多的优点。给出和分析了实验的结果     

An optical sensing system for the concentration of methane based on fiber Bragg gratings

Based on a special catalyst and fiber Bragg gratings (FBGs), an optical sensing system is proposed to measure the concen- tration of methane. The temperature of the catalyst rises rapidly as the concentration of methane increases, and hence it can be detected by an FBG-type sensor through monitoring the wavelength shift of the reflection spectrum. The experimental results show the good performances of our system, such as the high resolution and temperature stability.     

Highly stable fiber Bragg gratings written in hydrogen-loaded fiber

We demonstrated that the thermal stability of fiber Bragg gratings written in hydrogen-loaded standard fibers can be significantly enhanced by preirradiating the fiber with UV beam before writing gratings. Our experimental result shows that these gratings maintained more than 60% of their initial index modulation after 10 hours at 605/spl deg/C.     

Mode couplings in superstructure fiber Bragg gratings

The spectral characteristics of superstructure fiber Bragg gratings are analyzed numerically based on the coupled mode theory, simultaneously taking into account the counterdirectional guided mode coupling, codirectional and counterdirectional claddings mode coupling. The theoretical results were compared with experimental data and very good agreement was obtained