All-fiber add-drop wavelength-division multiplexer based onintermodal coupling

We demonstrate a novel all-fiber add-drop multiplexer by using a tilted Bragg grating written on a two-mode fiber and a mode-selective coupler. The device can be made potentially with low loss and low cost, useful for add-drop of a small number of channels in wavelength-division-multiplexing (WDM) communication systems     

Optical add-drop multiplexers with low crosstalk

We propose and demonstrate three new optical add-drop multiplexer (OADM) architectures with simple and compact configuration and excellent crosstalk performance. The OADMs use a single multiport optical circulator and either one or two narrow-band fiber Bragg gratings, depending on the crosstalk requirement     

Full Strain Tensor Treatment of Fiber Bragg Grating Sensors

Embedded fiber Bragg gratings can be subjected to arbitrary states of strain including shear strain. Such perturbations can cause coupling between polarization modes. Coupled-mode theory in Bragg gratings so far neglected this effect and only considered forward-backward coupling. Polarization mode coupling within a Bragg grating leads to interdependencies between Bragg reflection peaks which have so far been unaddressed. We formulate a full strain tensor treatment of fiber Bragg gratings, considering the coupling of the polarization modes within the grating. We give an approximation for the coupling coefficients affecting the polarization mode coupling and numerically solve the coupled-mode equations for representative states of strain. We show in which way shear strain affects the optical response of a grating and demonstrate how the fiber's beat length influences this characteristic.     

All-fiber WDM optical crossconnect using ultrastrong widely tunableFBGs

We demonstrate an all-fiber wavelength-division-multiplexed optical crossconnect using ultrastrong fiber Bragg gratings (FBGs) with wide tunability. These FBGs have 0.2-nm bandwidths and can be tuned over ~52 nm due to a novel grating preparation technique to reduce mechanical strength degradation. There is negligible distortion in the transmission spectra while tuning the grating, and the crossconnect architecture uses cascades of these gratings for WDM operation. The ability to tune these >98% reflectivity gratings completely out of the entire WDM signal band minimizes the leakage of unwanted signal power and leads to the improvements of >10-dB crosstalk and >0.6-dB power penalty compared with conventional gratings     

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     

Dispersion of cascaded fiber gratings in WDM lightwave systems

Fiber gratings operating in the transmission mode can provide high dispersion at wavelengths close to the Bragg resonance. When multiple gratings are cascaded for wavelength division multiplexing (WDM) applications, the net dispersion between the stop bands of any two consecutive gratings is significantly modified. We discuss the dispersion characteristics of such cascaded fiber gratings and propose a dispersion compensator for simultaneous compensation of group-velocity dispersion (GVD) for multiple channels of a WDM lightwave system. We also discuss the impact of the dispersion possessed by cascaded gratings on grating based add-drop multiplexers     

可调谐单纵模多波长光纤激光器的研究

为了实现对台阶高度和绝对距离等物理量的高精度干涉测量,采用在一个光纤激光器中构建多个激光谐振腔的方法,构建了能同时发出多波长激光的光纤激光器。每个激光谐振腔都利用掺铒光纤作为增益介质,利用光纤光栅作为波长选择元件,改变光纤光栅的布喇格波长,即可改变对应谐振腔的激光波长。各个激光谐振腔独立但部分重叠,在重叠区域利用光纤耦合器构成复合子腔,使每个激光谐振腔都是复合激光谐振腔,从而使每个激光谐振腔都发出单纵模激光。结果表明,该光纤激光器能同时发出功率和频率都稳定的多波长激光,且每个波长都是单纵模激光;在4h内,每个波长的波长稳定性优于0.01nm。该设计对可调谐单纵模多波长光纤激光器的研究是有帮助的。     

Dynamic OADM Using Tunable Sampled Bragg Gratings Based on Vernier Effect

A novel dynamic optical add-drop multiplexer（OADM） scheme using tunable sampled fiber Bragg gratings（SFBG） by Vernier effect is firstly proposed. In this scheme, broad wavelength tuning range is achieved by only slightly adjusting the SFBG, the wavelength tuning of OADM will be faster than traditional dynamic OADM.     

基于光纤光栅和二维编码的OCDMA分插复用

对基于布托格光纤光栅（FBG）和二维时域／频域编码技术的光码分多址（OCDMA）系统进行深入的研究，提出了一种新型的应用二维叫时域／频域编码技术的OCDMA码分插复用器（ADM）单元。设计的ADM单元基于FBG的编解码器结构性价比高，可以简单地从网络巾取下相应码的数据同时向网络中添加本地数据。最后，把所提出的ADM单元应用于高速OCDMA系统进行模拟仿真，性能良好。     

线性啁啾光纤布喇格光栅反射谱的数值模拟

为了研究线性啁啾光纤布喇格光栅的特性,并进一步把它用于光纤激光器上,介绍了线性啁啾光纤布喇格光栅的耦合模理论,采用4阶Runge-Kutta法和传输矩阵法结合控制变量法,对线性啁啾光纤布喇格光栅反射率与啁啾系数、半峰全宽与光栅长度、反射率与直流纤芯折射率改变量之间的关系进行了数值模拟。结果表明,线性啁啾光纤布喇格光纤可以展宽带宽。基于这个结论,提出了利用线性啁啾光纤布喇格光栅作为光纤激光器腔镜,使输出谱线展宽,从而可作为宽带光源使用的方案。     

线性啁啾光纤光栅变迹函数的研究

文中利用传输矩阵法对我们构造的四种变迹函数所描述的线性啁啾光纤光栅的光学特性进行了数值计算,并与常用的高斯型变迹线性啁啾光纤光栅的最佳光学特性进行了比较和分析,得出了一些有意义的结论,为设计和制作合适的线性啁啾光纤光栅用作色散补偿器提供了一定的理论依据。     

A novel dual-wavelength fiber Bragg grating and its application in fiber ring laser

A novel method for fabricating dual-wavelength fiber Bragg gratings (FBGs) by using one phase mask is developed. The method is based on a double-exposure technique. Our technique lends itself to writing gratings with controllable reflectivity and separation of two Bragg wavelengths. A grating with two equal transmission peaks of 20.25 dB is obtained by this method and the separation of the two Bragg wavelengths is about 0.8 nm. With the grating, we demonstrate a dual-wavelength erbium-doped fiber ring laser whose interval of the two peaks is 0.8 nm. The laser's peak powers can get 3.1 mW above and have a good stability.     

Simple Reconfigurable Photonic Microwave Filter Using an Arrayed Waveguide Grating and Fiber Bragg Gratings

We demonstrate a photonic microwave finite impulse response filter with reconfiguration and tuning capabilities. The filter is based on spectral slicing of a broadband source and optical fiber as a wideband dispersive medium. An arrayed waveguide grating and fiber Bragg gratings are used to select and vary the weight of the optical taps to achieve reconfiguration and tuning     

Fiber grating sensors

We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors     

Transversal Load Sensing With Fiber Bragg Gratings in Microstructured Optical Fibers

We present fiber Bragg grating based transversal load sensing with a highly birefringent microstructured optical fiber. For the bare fiber, the change of the Bragg peak separation under a transverse line load was simulated with a finite-element model and experimentally verified. We also show that microstructured optical fibers with fiber Bragg gratings can be successfully embedded in a carbon fiber reinforced composite material. The linear dependence of the Bragg peak separation to a transversal stress in the composite sample was measured to be 15.3 pm/MPa.      

WDM系统中啁啾光纤光栅带外色散的影响

对啁啾光栅阻带外的色散特性进行了深入理论分析，在WDM系统中往往需要光栅级联来完成单个光栅不能实现的功能，级联光栅时，前面光栅的阻带外色散要对接续在其后面的光栅产生影响，增大了光栅的时延波动。对光栅级相互间的影响进行了理论分析与实验验证，提出了降低光栅间相互影响的方法是降低调制或光栅切趾，在光栅级联时采用高阶高斯切趾的效果最好。     

Bragg gratings in multimode and few-mode optical fibers

Bragg gratings in optical fibers in multimode propagation are investigated experimentally and theoretically. Bragg gratings formed in optical fibers in multimode propagation show multiple reflection peaks or multiple transmission dips in the reflection or transmission spectra, respectively. For standard graded-index multimode fiber, the number of reflection peaks of a Bragg grating depends on excitation condition of propagating modes. The number of reflection peaks of a Bragg grating at around 1.55 μm is 19 for highly multimode excitation and 3-4 for lower order mode excitation. We analyze the phase-matching conditions of the propagating modes and identify half of the reflection peaks as the reflection to the same mode and the rest as the reflection to the neighboring modes. In dispersion-shifted fiber, a Bragg grating at around 0.8 μm in three-mode propagation shows three reflection peaks in the reflection spectrum. The temperature dependence of each reflection peak is similar to that of a conventional Bragg grating in single-mode fiber. Polarization dependence measured on a Bragg grating in multimode graded-index fiber is negligible. An advantage of Bragg gratings in multimode fiber (MMF) and the applications are discussed     

基于MZI和取样光栅的可调谐光分插复用器

提出一种基于马赫-曾德尔干涉仪(MZI)和取样光纤布拉格光栅(SFBG)的新型光分插复用器(OADM),它由两个并联马赫-曾德尔干涉仪和四个取样光纤布拉格光栅组成.对该光分插复用器的输出特性进行了理论仿真,研究得出通道间隔为0.8nm时下载和输出端口的光谱特性,研究发现干涉仪的臂长差和取样光栅的中心波长差是决定光分插复用器输出特性的主要因素.调节一个马赫-曾德尔干涉仪上的臂长差和取样光栅的中心波长,可以实现信号下载可调功能或直通功能.     

Design of High-Channel-Count Multichannel Fiber Bragg Gratings Based on a Largely Chirped Structure

We propose a novel technique to design a high-channel-count, multichannel fiber Bragg grating (FBG) based on a largely chirped structure. The minimization of refractive-index modulation has been widely discussed in the previously demonstrated multichannel grating designs. The complexity of the grating structure, however, is also important from the point of view of practical fabrication. In this paper, the degree of grating complexity (DGC) is defined. We show that the DGC of a multichannel grating can be significantly reduced by designing a grating with a largely chirped structure. A detailed grating design process based on this technique is discussed, by which four multichannel gratings are designed and numerically studied, for applications such as periodic and nonperiodic spectral filtering, chromatic dispersion compensation and dispersion slope compensation. The proposed theory and examples show that different gratings with high-channel-count and multichannel responses can be designed and fabricated using a single commercially available phase mask, and all the gratings can be realized by a conventional FBG fabrication facility since the gratings have a low DGC with low index modulation.