A Low Polarization Sensitivity All-Fiber Wavelength Measurement System

A low polarization-sensitive all-fiber wavelength measurement system using a twisted macro-bend fiber edge filter together with polarization-insensitive (PI) 3-dB coupler is presented. Eliminating the polarization-dependent loss (PDL) is essential when macro-bending single-mode fiber is utilized as an edge filter. A new bending configuration to eliminate the PDL of a fiber edge filter is proposed in this letter by twisting the fiber by 90$^{circ}$ between two bending sections with equal length. The PDL of this configuration retains a low value even while the bending length is increased to achieve a steeper response for the edge filter. This configuration together with a PI 3-dB coupler makes the system to have very low polarization sensitivity and as a result high wavelength accuracy can be achieved.      

All-fibre temperature sensor based on macro-bend singlemode fibre loop

An all-fibre temperature sensor is proposed based on a macro-bend singlemode fibre loop using a ratiometric power measurement scheme. The sensor has a linear characteristic with temperature at a fixed wavelength and bend radius. A direct linear relationship between the bend loss of the singlemode fibre and temperature is reported for the first time. By measuring the change in bend loss of the system a change in temperature can be measured assuming the system is calibrated. The proposed sensor has a higher temperature resolution than other conventional fibre-optic sensors and also benefits from simplicity.     

Tunable Bandpass Filter With Solid-Core Photonic Bandgap Fiber and Bragg Fiber

A tunable spectral bandpass filter which includes two fibers with different bend loss edges-a solid-core photonic bandgap fiber with short wavelength bend loss edge and a Bragg fiber with long wavelength bend loss edge-is presented in this letter. The central wavelength and the bandwidth can be widely tuned around 1100 nm by controlling the bend diameters of the two fibers respectively. It can be a low-loss in-line fiber device due to its all solid structure and standard splice connection.     

Novel Distributed Fiber Bragg Grating Sensing System Based on M-Z Interferometer

One of the problems in using grating sensors is how to measure a small Bragg wavelength shift accurately. Nowadays demodulation techniques are mainly based on the edge filter, tunable filter, or interferometric scanning methods. Interferometric demodulation is widely accepted as the technology which can provide the high sensitivity. An interrogation system using the interferometric scanning method is presented, in which an unbalanced fiber M-Z interferometer is used as the wavelength scanner for temperature measurement. A novel fiber Bragg grating sensor system based on M-Z interferometric demodulation technique is presented in this paper. The temperature sensitivity measured in the experiment is almost consistent with that obtained from the theoretic calculation.     

基于单向传输的光纤时延波动测量

为了与现有光纤通信网络兼容,研究了一种基于单纤单向传输的光纤时延波动测量方法。基于色散温变效应和Sellmeier等式,建立了利用温度的准确测量和双波长光信号传输时延差波动反推单向时延波动的比例模型。令模型中的比例系数是单波长时延波动和双波长时延差波动的比,仿真研究了温度和波长差对比例系数的影响。搭建了75 km光纤单向时延波动测量实验平台,实验结果表明:实测比例系数?258.4接近于理论比例系数?277.3,对应单向传输时延波动误差为660 ps,实验结果验证了模型的正确性和基于单向传输的光纤时延波动测量的可能性。     

The Temperature Dependence of Polarization-Dependent Loss for a Macrobending Single-Mode-Fiber-Based Edge Filter

The temperature dependence of polarization-dependent loss (PDL) for a macrobending standard single-mode fiber (SMF28) is investigated both theoretically and experimentally. The experimental results show an overall agreement with the proposed theoretical model over a temperature range from 0 $^{circ}$C to 70 $^{circ}$C. An SMF28-based edge filter is used as an example regarding temperature-dependent PDL performance. It is shown that the temperature variations have a significant influence on the polarization dependence of macrobending loss, and further impact on such a fiber bend loss edge filter used in a wavelength measurement application. It is also concluded that by using the proposed models, such a temperature-dependent birefringence can be beneficially predicted in bending fiber sensing applications.      

一种新的光纤布拉格光栅波长移位检测技术

提出了一种利用全光纤非平衡Mach Zehnder干涉仪作为边缘滤波器进行光纤布拉格光栅 (FBG)波长移位检测的方案。这种边沿滤波器具有梳状的滤波特性 ,且其两输出臂滤波特性互补。利用其一对滤波边沿 ,可以将被测光栅的波长信息转化为功率信息进行检测。在制作时 ,通过适当改变干涉臂长差可方便地调整测量范围和检测分辨率 ,具有较大的灵活性。以两种不同的比较运算的方法消除系统功率起伏对测量结果的影响 ,都得到了较好的结果。采用该检测方案进行了光纤布拉格光栅温度传感实验 ,得到了± 10 pm的波长测量精度。     

高精度准分布式光纤光栅传感系统的研究

利用一个经过温度补偿封装的长周期光纤光栅解调系统中所有测量点的传感光栅的波长漂移,实现了实时、高效解调的准分布式测量.理论研究表明该系统适用于对温度、应变等参量的多布点准分布式测量.并以温度为例从实验上研究了高精度的准分布式光纤光栅传感系统.通过改善每个测量点的测量精度来提高整体系统的测量精度.利用金属槽对传感光纤布喇格光栅进行增温敏封装,使其温度灵敏系数比普通裸光栅提高了3.6倍,并利用经过温度增敏封装的光栅作为传感元件,在110℃(-50 ℃-60 ℃)的动态范围内实现了精度为0.04- ℃的多布点准分布式温度测量,理论分析与实验结果一致.     

基于实时校准技术的光纤光栅传感解调系统

报道了一种采用实时校准技术的数字化光纤光栅传感解调方案。解调系统利用锯齿波电压信号和数字相位同步信号控制可调谐光纤法布里一珀罗(TFFP)滤波器，对光纤光栅传感器阵列进行扫描式寻址，同时采用非测量环境中的参考光栅和数字温度计提供精确的参考波长，并由高速数字信号处理器(DSP)实时校准滤波器的波长读取值，很好地消除了滤波器渊谐的温度漂移、非线性和蠕动性引起的测量误差。结果表明，实验系统的波长寻址范围为1520～1570nm，扫描频率为100Hz，波长测量分辨率为5pm，应变测量分辨率为4．13με。     

Highly sensitive FBG temperature measurement based on a wavelength pumped multiplexing filter and two optical channels

An improved demodulation system for fiber Bragg grating (FBG) sensors based on the wavelength pumped multiplexing (WPM) filter is presented. Double photoelectric measurement channels are exploited to compensate the surrounding and light source interference including temperature influence. Temperature testing is employed to prove the demodulation system capacity and characteristics. The digital thermometer and one free FBG are simultaneously introduced in the constant-temperature water tank for the comparison study. The results show that the demodulation scheme can measure temperature with a high resolution, stability and reliability. Its sensitivity of temperature measurement can reach 0.05 °C in repeated testing.     

弯曲光纤布拉格光栅光谱特性的研究

从理论与实验两方面研究了基于普通单模光纤的光纤布拉格光栅在弯曲时光谱特性的变化。基于耦合模理论, 以弯曲光纤为参考波导, 研究了弯曲波导的分析模型和漏模求解工具, 考虑了弯曲时光弹效应的影响, 得到弯曲光纤中的准导模（漏模）; 分析了弯曲情况下, 布拉格波长的变化情况, 与实验结果基本吻合。在1 cm的弯曲半径下, 布拉格波长向长波长的偏移在10-2nm量级。     

一种用于2~14 μm红外光谱辐射计的波长标定方法

针对所研制的基于渐变滤光片的高 分辨率宽波段红外光谱辐射计,提出了一种波 长标定方法。首先,由理论推导给出初始 波长,并对所用渐变滤光片的非线性进行校正。然后采用基 于波长基准源的特征峰匹配法进行波长校正,进而完成波 长标定。最后使用激光器对标定精度进行校验。结果表 明,本文方法的标定精度优于1%。     

一种新颖的多波长环形腔掺铒光纤激光器

提出了一种结构新颖的多波长环形腔掺铒光纤激光器 ,在其结构中采用了一种新型梳状滤波器 ,该滤波器由一个光纤光栅非对称写在一个Sagnac环中来实现 ,具有设计简单、易于制作、成本低和插入损耗小等优点。实验中得到了非常稳定的三波长和双波长激光输出 ,线宽均小于 0 0 6nm ,输出波长间隔分别为 0 34nm和 0 5nm ,输出功率差异分别在 2dB和 0 4dB内 ,消光比分别为～ 40dB和～ 5 0dB。     

蓝宝石光纤高温光学特性研究

实验研究了蓝宝石光纤在高温环境下(大于1000℃)的光学稳定性,以及光纤的自辐射、塑性弯曲对出射光信号的影响,结果表明蓝宝石光纤在高温下的光学传输损耗随时间增加,温度测量精度由信号的稳定性和光纤自辐射决定,而蓝宝石光纤的塑性弯曲引起的信号额外损耗比较小,在900nm处小于0.1 dB.光纤表面在高温下的永久损伤是产生这些性能劣变的主要原因,损伤的主要机制为外部杂质在高温下与光纤表面的相互作用.

Abstract：

The performance stability,self-radiation and plastically bend of sapphire fiber under high temperature are studied.Experimental results show the optical transmitter loss increases with time when sapphire fiber under high temperature environment.Temperature measurement precision depends on the stability of signal and the self-radiation of fiber.The additional loss caused by a single plastically bend is less than 0.1 dB at 900 nm,less than the loss.before bend.The permanent injury of the sapphire fiber surface is the main reason for deterioration.It is found that the surface injury is mainly attributed to the pollution of the fiber surface and the mutual reaction between the sapphire fiber and the polluted substance in the ambient environment.     

An equivalent step-index model for single-mode fibers based onmatching of bend loss and spot size at one wavelength: a simulationstudy

A method for the determination of equivalent step index (ESI) parameters for a given single-mode fiber is presented. The method is based on the matching of bend loss characteristics and (Petermann II) spot size at one wavelength. Numerical simulation studies have been carried out for fibers with parabolic and triangular index profiles having zero total dispersion at 1300 or 1550 nm. The results show that the method gives a model that is both stable with respect to the matched wavelength in the 1500-1600-nm range and accurate for predicting fiber characteristics such as spot size, waveguide dispersion, bend loss, and the cutoff wavelength (of the next higher mode) over this range of wavelength     

Integrated AlGaAs waveguide components for optical phase differencemeasurement and correction

A Y-junction interferometer phase measurement technique has been developed that is independent of the power or power ratio in the input arms. This technique was incorporated into a proof-of-concept AlGaAs guided-wave Mach-Zehnder interferometer to demonstrate the measurement and correction of a phase difference between the arms. In the first part of this paper, we describe the design, fabrication, and characterization of the individual AlGaAs dielectric-loaded rib waveguide components that were chosen to fabricate the proof-of-concept interferometer. These components include passive waveguides, bends and Y-junctions, and reverse-biased phase modulators. The composition of the waveguide layer was chosen so that these modulators would have low loss at the applied voltage required for maximum phase correction. The choice was based on electroabsorption measurements on test modulators as a function of the energy difference between the bandgap of the waveguide layer and the operating wavelength. The average propagation loss at 862 nm of the passive single-mode guides used was 1.1 dB/cm. The abrupt bend insertion loss was ~0.20 dB/bend for a 0.5° bend angle, and the Y-junction insertion loss was ~0.37 dB for 1.0° full angle. Two-mm-long p⁺ -n^--n⁺ phase modulators typically had V_π voltages of ~6.8 V. On a slightly modified structure, V _π voltages as low as 2.65 V were measured. In the last part of the paper, the proof-of-concept interferometer and test setup are described and recent phase difference measurement and correction data with intentional power imbalances greater than 90% between the interferometer arms are presented. These results demonstrate conclusively that the phase difference measurement and correction performance of the Y-junction interferometer technique are independent of the power ratio in the interferometer input arms for power ratios >10:1     

一种全光纤电流传感器温度补偿方法

为了解决传感光纤的弯曲、扭转以及外界工作环境的变化导致全光纤电流传感器测量精度降低的问题,提出了一种基于输出椭圆偏振光长轴斜率的全光纤电流传感器温度补偿方法。论证了椭圆偏振光长轴斜率能够反应输出椭圆偏振光的光椭率的大小,利用TMS320F28335和对应算法求出斜率,实验中使用输出椭圆偏振光长轴斜率对传感器进行修正并进行了实际测量。结果表明,基于该修正方法的测量系统,实现了在单次变温条件20℃~60℃内变化时测量结果偏差满足0.2s。这一结果对全光纤实用化研究是有帮助的。     

光纤光栅布喇格波长随温度和应力的变化特性及其补偿

主要用实验数据简要叙述了光纤光栅中布喇格波长随温度和应力变化呈良好的线性关系,并介绍了一种温度补偿装置,能有效抑制光纤光栅的布喇格波长随温度的漂移。     

基于最小二乘法的电力电缆FBG传感测温系统

为了提高电力电缆测温系统的测量精度和速度,提出了以光纤梳状滤波器代替参考光栅提供拟合数据参考点,采用最小二乘法拟合光纤Bragg光栅波长和F-P可调谐滤波器调谐电压的线性关系,通过F-P可调谐滤波器解调FBG传感器中心波长变化的方法,完成对电力电缆温度的测量.研究表明,光纤梳状滤波器能够代替多个恒温参考光栅实现波长标定,对反射波长的测量误差＜5pm,温度均方误差≤0.7 ℃.     

Highly accurate long-span chromatic dispersion measurement system by a new phase-shift technique

A highly accurate long span chromatic dispersion measurement system, which is based on a wavelength-division-multiplexing phase-shift technique and utilizes six laser diodes in1.2 sim 1.6 mum spectral region, has been developed. It is intrinsically free from error due to the fiber length variation caused by temperature changes under the measurement. The measurement accuracies of dispersion and Zero-dispersion wavelength are extremely good and within ±0.02 ps/km . nm and ±0.1 nm in 1250 ∼ 1450 nm spectral region in the case of a 10.5-km single-mode fiber measurement. The dynamic range is over 50 dB excluding system theS/Nmargin of 5 dB. Using this system, chromatic dispersion measurements of a 101.9-km pure-silica-core single-mode fiber and a 100.7 km concatenated dispersion-shifted single-mode fiber have been successfully carried out. The measured result has coincided with the arithmetical mean of those of constituent fibers.