双折射光纤环形镜滤波器特性研究

双折射光纤环形镜具有滤波特性,将两个串联的双折射环形镜作为光学滤波器可以改善滤波特性,使其更为灵活。提出了用两个双折射光纤环形镜相串联的简单方案改善环形镜滤波特性。分析了由双折射光纤和萨尼亚克环构成的环形滤波器的透射特性,并讨论了用两个双折射光纤环形镜串联的滤波特性。从理论上模拟了双折射光纤长度比为1：2时的透射光谱形式,给出了透射光的表达式。串联后光谱中主峰的3dB带宽约为7nm,与单个环形镜相比,压缩了环形镜的3dB带宽,品质因数Q约为4．5。实验结果与理论模拟相一致,因此证实了该理论的正确性。     

高双折射光纤环镜改善40 GHz光时钟消光比的研究

时钟信号的好坏在同步、解复用和光判决中起着决定性的作用,双折射光纤环镜具有灵活可调的滤波特性,光时钟信号通过双折射环形镜可以使其消光比得到改善,从而提高时钟信号的质量。为此提出了利用高双折射光纤环形镜提高光时钟信号消光比的方案,数值上模拟了环形镜透射谱随双折射器件偏振延时量(Δt)、偏振控制器快慢轴角度以及偏振控制器所引入光程差的变化而变化的情况,并理论分析了消光比不理想的时钟信号经过环形镜后的光谱形式。用法布里-珀罗滤波器提取的40 GHz时钟信号进行实验,时钟经过环形镜后消光比改善了13 dB,实验结果和理论模拟得到了很好的匹配。     

级联双折射光纤环镜滤波特性的分析

从理论上研究了级联双折射光纤环镜滤波器的滤波特性，给出加隔离器与不加隔离器两种不同结构的串联双环镜滤波器透射光强的表达式，并对于两个环镜取不同的周期比时的滤波特性进行了数值模拟和分析.得出串联环镜滤波效果与级联顺序无关，光隔离器对滤波效果不会产生影响，只是增加了插入损耗.通过级联和改变两个环镜的双折射光纤长度比，可以获得不同的滤波效果.最后给出了多个环镜直接级联后透射光强的通项表达式，通过对通项式的理论分析可以设计不同的滤波器.     

基于过耦合器的L波段可变波长掺铒光纤激光器

研究了一种新型的光纤环形镜(FLM)的原理和特性,这种FLM是由耦合比对波长变化的耦合器即过耦合器和偏振控制器(PC)构成,改变PC的状态,可以调节环的反射谱位置和深度.与高双折射光纤环形镜构成线型谐振腔,调整光纤环内PC的状态可以改变环对不同波长的反射率,控制腔内的增益从而输出可变波长的激光.实验得到输出波长在156...     

利用偏振控制器连续调节光纤环镜的反射率

研究了一种新型光纤环镜(FLM)的原理与特性，这种FLM由在普通光纤环镜中插入光纤型偏振控制器(PC)构成.通过等效光路分析建立了该FLM的理论模型，并对其反射特性进行了数值模拟.研究表明，通过改变PC的状态，即改变其双折射效应的快轴取向或强度，可连续调节FLM的反射率，反射率谱具有宽带特性，主要受光纤耦合器工作带宽的影响.此外，对FLM的反射特性还进行了实验研究.实验结果也证实，通过调节PC状态，FLM反射率可在其最大和最小值之间连续调节，实验测得FLM最大和最小反射率分别可达93%和2%.根据PC双折 关键词： 光纤环镜 偏振控制器 光纤耦合器 反射率     

基于多模干涉滤波器和双折射滤波器的四波长可开关光纤激光器

设计了一种基于多模干涉滤波器和双折射滤波器的四波长可开关光纤激光器,理论分析了多模干涉滤波器和双折射滤波器及其级联结构的滤波特性.双折射滤波器能有效地抑制多模干涉滤波器的不规则边模.保偏掺铒光纤同时作为增益介质和滤波元件,优化多模光纤长度和保偏掺铒光纤长度保证了波长间隔的最佳匹配,级联滤波器的滤波周期为4.89 nm.调节偏振控制器,光纤激光器实现了单波长、双波长、三波长以及四波长可开关激光输出,输出激光的边模抑制比均大于40 dB,1h内波长波动均小于0.1 nm.     

高双折射光纤环镜轴向应变灵敏度研究

理论推导了高双折射光纤环镜轴向应变灵敏度公式,讨论了在高双折射光纤材料和入射光源不变的前提下,高双折射光纤长度以及作为敏感元件的传感长度与传感器轴向应变灵敏度的关系,讨论了入射光源相同时高双折射光纤材料与传感器轴向应变灵敏度的关系。结果表明：在高双折射光纤材料和入射光源不变的前提下,高双折射光纤环镜波长变化与轴向应变成线性关系,线性灵敏度为高双折射光纤材料和入射光源中心波长决定的常数,与接入的高双折射光纤长度、作为敏感元件的传感长度无关。     

监测点波长对高双折射光纤环镜轴向应变灵敏度的影响

研究了高双折射光纤环镜监测点波长对轴向应变灵敏度的影响. 经理论推导得出高双折射光纤环镜轴向应变灵敏度公式. 结果表明: 当高双折射光纤材料选定后, 灵敏度随着监测点波长的增大而增大; 当监测点选定后, 监测点的灵敏度为常数, 波长变化与应变成线性关系. 实验选取不同波长的波峰进行应变灵敏度监测, 对各监测点进行数据拟合, 实验结果与理论分析一致. 研究结果对提高高双折射光纤环镜应变、温度等灵敏度具有指导意义. 关键词： 波长 灵敏度 监测点 高双折射光纤环镜     

基于非线性偏振旋转效应的多波长光纤激光器

多波长光纤激光器是未来波分复用光通信系统的理想光源,提出和展示了一个基于非线性偏振旋转效应的多波长光纤激光器,非线性偏振旋转诱导的强度相关非均匀损耗能有效地抑制均匀加宽增益介质掺铒光纤中的模式竞争,从而使光纤激光器在室温下产生稳定的多波长输出,实验实现了最多18个波长的多波长输出.另外,此激光器没有使用传统的滤波器,而是在激光腔内插入一段保偏光纤,保偏光纤与偏振相关隔离器构成一等效Lyot双折射光纤周期性滤波器.利用这种在线型的双折射光纤滤波器简化了光纤激光器的结构,使它更易于集成.还实验研究了多波长输出随抽运功率的演化,发现抽运功率对多波长的均匀性影响很大.     

双环、三纤互耦全光纤熔锥滤波器用正常色散的双折射光纤所作的暗孤子开关的开关条件

通过将熔锥结构中强、弱耦合段的总幅度耦合系数与滤波网络方程中的幅度耦合系数等效的方法,定量分析了双环、三纤互耦滤波器的频谱特性。实验滤波器通带特性的测试结果与理论分析基本吻合。所测滤波器的中心波长、抑制度、半功率带宽及插入损耗分别为1.27 μm,>13 dB、72 μm及3.9 dB。在正常色散的双折射光纤中传输的暗孤子对之间由于耦合周期性交换能量,一个暗孤子可把能量完全转给另一暗孤子,因此双折射光纤可作光开关。本文讨论了椭圆角为35°的双折射光纤的开关条件,发现脉冲只有以特定的极化角入射才有开关现象产生,而且建立了光纤长度与孤子对相差、初始能量差的解释关系。     

Theoretical analysis of feedback high birefringence fiber loop mirror for application in single-frequency fiber lasers

A feedback high birefringence fiber loop mirror with a piece of erbium-doped fiber and a polarization controller is newly proposed. When the erbium-doped fiber is properly pumped to offset the loss of the feedback ring in the loop mirror, narrowband transmission peaks with large effective free spectral range can be achieved by the intrinsic vernier effect between orthogonally polarized lights respectively traveling along the two primary axes of the high birefringence fiber. In addition, the side transmission suppression ratio can reach about 6 dB. These special properties are independent of the polarization state of the input signal, which makes it feasible for the proposed feedback high birefringence fiber loop mirror to be employed as a narrowband filter in single-frequency fiber lasers.     

A novel double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror

In the paper, a ring double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror filter is demonstrated, in which the non-linear amplified fiber loop mirror (AFLMF) is used as a filter. At the 980 nm pump power of 10.29 dBm, the tunable laser source center wavelength of 1563 nm and power of −3 dBm, up to 12 even output channels with 0.16 nm spacing are achieved. At the same time, we study the influence of 980 nm pump power, the polarization controller and the tunable laser source center wavelength on the number of Stokes light wave.     

Three methods for improving an axial strain sensitivity of polarization maintaining fiber loop mirror

Sensitivity is one of the important performances for sensor. Theoretical results show that we can choose a long wavelength monitoring point, a high strain dependent birefringence coefficient polarization maintaining fiber (PMF) and a low birefringence PMF to improve the axial strain sensitivity of PMF loop mirror, and experimental results show that the axial strain sensitivity has respectively been improved by 8.06, 30.73, and 22.26% by these methods. The advantage of these methods is to improve the axial strain sensitivity without increasing system complexity. These results help to improve the temperature, displacement, torsion, curvature and liquid level sensitivities of PMF loop mirror. These results can also be applied in photonic crystal fiber loop mirror.     

基于多波长激光器的带通微波光子滤波器设计

提出了一种基于多波长光纤激光器的可调谐的带通微波光子滤波器。它以可调谐多波长光纤激光器作为光源,将相位调制器和色散器件相结合,通过在普通单模光纤中相位调制到强度调制的转换效应消除了低频谐振峰实现了带通微波光子滤波器。利用双折射光纤环镜输出谱中的一个窗口对多波长激光信号频谱进行加窗处理,使微波光子滤波器的边瓣抑制比提高了约11dB。通过调节多波长光纤激光器中的偏振控制器可以使输出多波长激光信号的相邻波长间隔得到调节,从而结合普通单模光纤的色散延时作用可以使微波光子滤波器的通带中心频率在7.66GHz范围内调谐。     

基于偏振干涉的光纤光栅传感解调方法

提出了一种新型的应用于光纤布拉格光栅传感器的波长移动探测方案.研究基于保偏光纤的光纤环镜结构并建立理论模型,分析其输入光波长和输出光功率分配特性并进行数值仿真和实验验证.结果证明该装置结构简单、稳定性好、检测精度高且可通过调整光纤环镜参数调节测量范围和精度.在大于１ nm解调范围内,波长平均解调精度小于1 pm. 关键词： 传感解调 偏振干涉 光纤环镜     

Compensation of polarization-dependent loss in transmission fiber gratings by use of a Sagnac loop interferometer

We analyze the transmission characteristics of a Sagnac loop interferometer containing a polarization-dependent loss element and lossless polarization-converting elements by use of Jones matrices. We show that polarization independence in the transmission mode can be achieved in such a configuration and that maximum transmittance occurs when a half-wave plate is used for the polarization-converting element. The result is verified experimentally for a fiber acousto-optic tunable filter and cascaded long-period fiber gratings with either intrinsic or process-induced polarization-dependent filtering characteristics.     

A novel temperature and strain sensing method based on high-birefringence fiber loop mirror

A novel temperature and strain sensor based on a fiber loop mirror (FLM) consisting of high-birefringence polarization-maintaining fibers is proposed. The output spectrum was theoretically deduced based on Jones matrix. Two equal-length high-birefringence fibers (HBFs) with different birefringence indices were inserted into the FLM. The temperature and strain sensing system was built. The sensitivity coefficients of temperature and strain were calibrated respectively. The double parameters measurement of temperature and strain was realized. High resolution of 2.38 μ? has been achieved for strain sensing. Meanwhile, the temperature resolution is 0.016 °C.