Narrowband fiber grating filters

Two techniques for the fabrication of fiber gratings with a narrowband filter response are reported. In the first technique, the reflection bandwidth is reduced by increasing the grating length. Fiber gratings 10 mm long have been made with a bandwidth of ~0.3 nm. In the second technique, a phase shift is incorporated into the grating to form a resonant structure. Fiber resonators with resonant dips in reflection and peaks in transmission having full-width half-maximum (FWHM) bandwidths of ~0.08 nm have been fabricated. A corresponding narrowband transmission peak was also measured     

用于FBG解调的AWG芯片的设计、仿真与制备

设计、仿真并制备了一种用于光纤布拉格光栅(FBG)解调的阵列波导光栅(AWG)芯片。该芯片基于SOI衬底进行制备,并在AWG的输入/输出波导、阵列波导与平板波导之间采用双刻蚀结构进行优化。经仿真,该AWG的插入损耗为1.5dB,串扰小于 -20dB,3dB带宽为1.5nm。优化后的AWG芯片采用深紫外光刻技术、电感耦合等离子体等技术制备。经测试,该AWG的插入损耗为3dB,串扰小于 -20dB,3dB带宽为2.3nm。搭建了基于该AWG的解调系统,解调实验结果表明,该系统在0.8nm范围内的解调精度可达11.26pm,波长分辨率为6pm。     

Experimental Study of MLSE Receivers in the Presence of Narrowband and Vestigial Sideband Optical Filtering

We report on experimental investigations of real-time maximum-likelihood sequence estimation (MLSE) in the presence of narrowband optical filtering, using 10.7-Gb/s nonreturn-to-zero ON-OFF keying and a fiber grating filter with 6.25-GHz bandwidth. Compared to standard threshold detection, the MLSE eliminates a 10^-3 error floor due to narrowband optical filtering and results in DFB a <2-dB optical signal-to-noise ratio penalty at a 10^-3 bit-error ratio. Furthermore, we demonstrate the ability of the MLSE to simultaneously compensate for narrowband optical filtering and chromatic dispersion. Finally, we investigate the influence of narrowband filter frequency detuning and show that the well-known effect of increased filtering tolerance given by the vestigial sideband effect observed in standard threshold detection, disappears in the presence of the MLSE.     

基于轴向压缩技术的宽调谐光纤光栅滤波器的研制

研制了一种宽调谐光纤光栅滤波器。该滤波器通过光纤插芯导引光栅,利用轴向压缩技术,实现了25nm的调谐。调谐过程中,FBG布拉格波长改变量与微位移台调节量呈良好的线性关系,FBG反射率波动小于0.59dB,3dB带宽波动小于0.1nm,装置稳定性较好,布拉格波长在30分钟内的漂移量小于0.07 nm。     

体布拉格光栅光谱滤波器特性研究

高透过率、窄光谱带宽、高抑制比的滤波器件是提升光学系统光谱纯度的核心部件，也是近年来新型光学器件领域研究的热门方向。传统的滤波器件不能够同时满足透过率、光谱带宽以及带外抑制的要求，而文中研究的体光栅作为一种新型的光栅，衍射效率大于90%，光谱带宽在100 pm左右，并且拥有一定的角度滤波特性。依据耦合波理论，理论仿真了各个光栅参数（光栅厚度、折射率调制度、光栅周期、光栅倾角）对光栅衍射效率及光谱带宽的影响，定量地给出了参数影响的大小，为体光栅的设计提供了理论指导。设计了体光栅测试系统，通过实验验证了体光栅的衍射效率、光谱带宽、角度选择性，实验结果与理论较为符合，为体光栅的实际应用提供了实验数据支持。     

基于双金属结构的光纤光栅温度不敏感滤波器

为提高光纤陀螺宽谱光源的平均波长稳定性,提出了一种用60μm超短光纤光栅制作带宽11.77 nm温度不敏感滤波器的方法。利用金属材料的热膨胀系数差,设计了双金属温度补偿结构,能够随温度的升高/降低对光纤光栅压缩/拉伸,有效地补偿光纤光栅由热光效应引起的波长变化。在30～60℃的温度范围内,光纤光栅的温度灵敏度系数为0.15 pm/℃,较未补偿前降低了60倍以上。该结构具有较好的温度不敏感性,可作为光源滤波器提高光源的平均波长稳定性并有望用于高精度光纤陀螺。     

Narrow-band optical channel-dropping filter

Waveguide couplers are combined with λ/4 shifted distributed feedback (DFB) resonators to produce narrowband channel dropping filters. The bandwidth of the filter can be made much narrower than the stopband of the grating. It is possible to remove the spurious responses of the grating filter by appropriate dispersion characteristics for the coupled waveguides. However, in some practical applications it may not be necessary to do this, if all channels can be accommodated within half the grating bandwidth of the filters     

基于色散光纤环级联结构的可调谐带通微波光子滤波器

提出并验证了一种宽调谐带宽的带通微波光子滤波器设计方案。该滤波器借助可调谐光纤光栅Sagnac环对宽带光源进行均匀切割,产生波长间隔可调的连续光载波作为滤波器的抽头,结合色散光纤环级联结构,实现滤波器的可重构性。研究结果表明,在光电调制器和光电探测器的频率带宽足够大的情况下,当光纤光栅Sagnac环的臂长差在0.50~8.28mm内变化、可调谐光纤延迟线的最小变化步长为0.01mm时,该方案能够实现滤波器中心频率在8.0506~1333.2000GHz内调谐,调谐步长为161.01MHz,边瓣抑制比达到27dB。     

Ultra-broadband optical filter based on chirped long-period fiber grating using leaky mode coupling

An ultra-broadband optical filter was proposed and demonstrated based on leaky mode coupling in a coated chirped long-period fiber grating (CLPFG). The CLPFG was coated with a material whose refractive index (RI) was higher than that of the fiber cladding, enabling the coupling of the core mode to leaky modes, to achieve a desired coupling efficiency. Complex coupled-mode theory was used to investigate the power evolution of the core mode that resulted from the coupling. From this, the conditions in which the core mode power attenuates the most rapidly were identified. In addition, phase matching turning point (PMTP) was used in the design, to overcome the conflict between the range of grating period change and the grating length in the CLPFG. Finally, an optimized CLPFG-based filter with a length of 3.5 cm was obtained, which has a symmetrical attenuation band with an operating bandwidth over 300 nm. Within the operating bandwidth, the flatness is less than 2.5 dB and the transmittance is lower than 0.1%.     

单偏振双波长非保偏有源掺杂光纤激光器

利用宽带保偏光纤光栅(PFBG)、普通有源光纤和窄带普通光纤光栅构成独立的谐振腔,且窄带普通光纤光栅的中心波长分别与保偏光纤光栅的一个反射峰波长对准,可以输出稳定的双波长/单波长的单偏振激光.利用这一思想,制成了基于非保偏有源掺杂光纤的单偏振双波长光纤激光器.实验结果表明,双波长同时激射时的激光消光比为46.7 dB,单波长激光的消光比为59.6 dB,滤波出单波长测量其偏振度为98.5%.这种激光器在微波光子领域可用于在光域产生微波.     

基于电弧等离子体的光纤光栅快速退火的研究

为了实现光纤布喇格光栅的快速退火,采用高温电弧等离子体热处理光纤光栅的方法,设计了相关实验进行验证。由实验可知,透射谱深度23dB、中心波长1552.09nm、3dB带宽0.2784nm的光纤光栅,经电弧等离子体放电扫描后,光纤光栅的透射谱深度减小,3dB带宽变窄,中心波长蓝移;随着重复扫描次数的增加,各参量变化趋势减缓,最终透射谱深度减小13dB、中心波长蓝移0.84nm、3dB带宽变窄0.1013nm;将电弧等离子体处理后的光纤光栅放入高温炉24h退火后,透射谱深度、中心波长、3dB带宽均不再发生变化。结果表明,将电弧等离子体用于光纤布喇格光栅的退火处理是可行的,并且具有周期短、涂覆层无损伤的优点。     

光纤光栅解调系统的寻峰算法研究

为了提高光纤光栅波长解调系统的反射谱寻优精度,利用遗传算法的未成熟收敛性进行了研究.阐明了遗传算法提高解调精度的原理,以可调谐F-P腔的光纤光栅解调系统为基础,验证了算法的可行性和可靠性.使用MAT-LAB对F-P腔滤波光纤光栅解调系统的反射光谱进行寻峰,得到传感光纤光栅的中心波长.分析了算法中初始种群数量、遗传代数、变异率对的寻优结果影响,并得到一组最佳遗传算法参量.算法精度达到3pm数量级,50次重复计算数据标准差小于0.5pm.结果表明,该算法稳定高效、实用性强,可以显著减小噪声对光纤光栅传感系统的影响,提高解调精度.     

L 波段带双零点的窄带LTCC 滤波器设计

本文应用LTCC 技术设计了一个L 波段二阶Chebyshev 窄带带通滤波器。该滤波器集成在9 层LTCC 介质中,采用等效集总元件（电容电感)结构,充分利用LTCC 的三维封装结构减小滤波器体积,通过谐振单元中集总元件的串并联产生两个带外传输零点,同时调整谐振单元耦合间距控制带宽。滤波器输入输出利用金属通孔将带状线过渡到微带上。滤波器（带过渡结构）的仿真结果为：中心频率1.42 GHz,1 dB 相对带宽2.1%,插入损耗通带内最低0.5 dB, 回波损耗优于20 dB,整个滤波器体积为：4.5×4×0.87 mm3。     

一种基于高衰减光纤的光纤光栅热线式流量计

为了发展全光学流量测量技术,提出了一种基于掺钴高衰减光纤的光纤光栅热线式流量计。通过解调光纤布拉格光栅(Fiber Bragg Grating, FBG)中心波长进行流量测量,具体包括传感器制作、温度传感特性测定和流量测量实验。结果表明,基于衰减系数为8.9 dB/cm、工作波长约为1480 nm的掺钴光纤的FBG具有10.3 pm/℃的温度灵敏度;流量计在400～3700 L/h液体流量范围内可高重复性地实现测量;流量--FBG中心波长遵循特定非线性函数计算模型;流量计的平均灵敏度约为0.15 pm/(L·h^-1),低流速下灵敏度最高可达到1 pm/(L·h^-1)。所提出的流量计丰富了光纤光栅用于液体流量测量的研究。设计中采用了掺钴高衰减光纤自发热和单端毛细管封装,为流量传感器的全光学化、微型化和高灵敏度发展提供了新思路。     

基于双LPFG解调的高灵敏度振动检测系统

基于边缘滤波解调原理,提出了一种利用双长周期光纤光栅（LPFG）解调光纤布拉格光栅（FBG）振动传感信号的新方法。利用传输光谱叠加后的双LPFG作为边缘滤波器,增大了FBG传感信号解调灵敏度。静态实验结果表明,利用单、双LPFG作为滤波器解调的灵敏度分别为-1．1965dB／nm和-2．4836dB／nm,双LPFG解...     

Superconducting Ultrahigh Q Tunable RE Preselector

The application of superconductivity to the problem of reducing radio frequency interference (RFI) is described. A lowloss, extremely narrowband superconducting filter was developed that is tunable from 6.3 to 21 MHz. This filter has an unloaded Q of 350 000 to 600 000 over the tuning band, bandwidth adjustable from 60 Hz to 50 kHz, calibrated external controls for frequency tuning and bandwidth adjustment, and good resettability and stability. An optimum circuit design provides minimum bandwidth variation with frequency tuning and minimum resonant frequency variation with changes in bandwidth. Performance tests on high-frequency receivers showed reductions in intermodulation interference susceptibility of 40 dB and improvements in FSK Teletype signals of 23 dB.     

基于柔性铰链结构的高灵敏度低频光纤光栅加速度传感器

设计了一种基于柔性铰链结构的光纤光栅加速度传感器,进行了结构理论分析,并构建有限元模型仿真分析了传感器的加速度传感特性。基于F-P滤波器构建了具有温度自补偿功能的光纤光栅加速度检测系统,并通过增加反馈控制电路,对F-P滤波器进行反馈控制,实现了系统的零点自温度补偿。对系统的特性进行了实验测试,结果表明:系统对加速度的连续激励信号和冲击激励信号均有良好的动态响应,系统的固有频率为380.0 Hz,动态响应范围可达65.6 dB,频率响应范围为10.0 ~240.0 Hz,灵敏度为236 pm/g,所设计的加速度传感器具有较强的横向抗扰能力,干扰方向灵敏度仅为工作方向灵敏度的3.5%。     

Multiwavelength Fiber Optical Parametric Oscillator

We demonstrate, for the first time to the best of our knowledge, a multiwavelength fiber ring laser using a continuous-wave dual-pump fiber optical parametric amplifier (FOPA) as gain medium. In the ring cavity, two high-power pumps are injected into a spool of 1-km highly nonlinear dispersion-shifted fiber to generate the parametric gain, and a superimposed chirped fiber Bragg grating is used as the comb-like filter. Benefiting from the high and flat gain of the dual-pump FOPA, seven lasing lines around 1.55 mum with wavelength spacing of 1 nm have been obtained. Each lasing line has a linewidth of as narrow as 20 pm and an extinction ratio of > 30 dB. The proposed mechanism using a dual-pump FOPA as gain medium is a promising alternative for generating multiwavelength laser.     

双信道解复用长周期光纤光栅的实验研究

长周期光纤光栅是近几年出现的一种波长选择滤波器件。利用其波长选择损耗特性,提出将之用于1310nm/1550nm波分复用系统的解复用。采用电弧熔融刻槽的方法,制备了长周期光纤光栅。并通过控制电弧放电过程和光栅的周期长短及周期数,得到了较为理想的谱特性。结果显示,其通道插入损耗能够小于0.5dB,20dB损耗阻带带宽可达15nm,信道隔离度估计约25dB。     

S-band gain flattened distributed fiber Raman amplifier with chirped fiber bragg grating filter

IPTV,video-phone,video-conference,distance learn-ing,distance medical ,e-governmental affairs ,etc .will be-come commonthings in people' s daily life with the fastdevelopment of Internet technology.During this processextra-capacity of fiber communication …