A highly efficient polarized superfluorescent fiber source for fiber-optic gyroscope applications

We demonstrate a novel polarized superfluorescent fiber source (SFS) that increases the output power in the desired polarization by a factor of 1.96 over that of an unpolarized SFS at the same pump. This is achieved by inserting a polarizer at the optimal point in the bidirectionally pumped erbium-doped fiber of an unpolarized SFS. Stable pump-power-dependent mean wavelength operation and less sensitivity to the insertion loss, important for fiber-optic gyroscope applications, are obtained in this configuration.     

A single-polarization fiber

We report an oPtical fiber which guides only one polarization. This fiber polarizer utilizes high modal birefringence (4.7 times 10^{-4}) to split the two polarizations of the fundamental mode and an ellipitcal depressed-index cladding to provide a steep wavelength-dependent tunneling loss to the fast axis mode. The stress-induced birefringence is created by an elliptical SiO2-B2O2inner cladding. A 4.7-m length of polarizer fiber exhibits an extinction ratio of 34 dB at a wavelength of 633 nm, with polarizing behavior over a bandwidth of 50 nm. Insertion loss of less than 1 dB has been observed for the guided linear-polarization mode. The polarizing band may be shifted from 620 to 525 nm by bending the fiber to a radius of 0.67 cm. Such fiber polarizers should find a variety of applications in fiber sensors, attenuators, isolators, wavelength filters, and tuners.     

Polarized Superfluorescent Fiber Sources

We report the theoretical and experimental performance of new, linearly polarized superfluorescent fiber sources (SFS). Internal polarization is produced either by splicing a fiber polarizer at an optimum location along a standard Er-doped SFS or by using a single-polarization Er-doped fiber. Numerical simulations predict that when operated in the backward, forward, or double-pass configuration, these SFSs produce nearly twice the power in the desired linear polarization as a standard, unpolarized SFS. This efficiency figure depends weakly on the polarizer location and extinction ratio, but requires a low polarizer insertion loss ( < 0.5 dB). Laboratory prototypes of a backward and a forward polarized SFS are presented that exhibit a power output in the desired linear polarization about 1.75 times larger than that of an unpolarized SFS, and an extinction ratio in excess of 17.5 dB.     

In-line optical fiber polarizer and modulator coated withLangmuir-Blodgett films

In-line optical fiber polarizer and modulator were fabricated by depositing Langmuir-Blodgett (LB) films on polished fiber surface with gold layer. The thickness of LB film was adjusted by changing the number of monolayers, which then optimized the performance of the fiber polarizer. Good agreement was observed between the theoretically predicted conditions for efficient coupling and the experimentally determined conditions for high TM/TE extinction ratio of the optical field. By applying an electric field between the LB film, the polarization state of the lightwave in the optical fiber can be modulated     

Linearly polarized polarization-maintaining Er3+-doped fluoride fiber laser in the mid-infrared

We demonstrated the ~2.8-μm and ~3.5-μm linearly polarized continuous wave (CW) laser outputs from a polarization-maintaining (PM) Er3+-doped fluoride fiber laser. By introducing a film polarizer into the cavity to select the laser polarization orientation, the ~2.8-μm linearly polarized CW laser with a high polarization extinction ratio (PER) of ~23 dB and maximum output power of 2.37 W was achieved under double-end pumping at 976 nm. By adding another 1981-nm pump source simultaneously, the ~3.5-μm linearly polarized CW laser was also obtained, giving higher PER of ~27 dB and maximum output power of 307 mW which is only limited by the available power of 1981-nm pump. To the best of our knowledge, this is the first report on a mid-infrared linearly polarized CW PM fiber laser in the >2.5-μm mid-infrared region. This work not only opens up opportunities for some new mid-infrared applications, but also provides a promising platform for developing high-stability and versatile mid-infrared laser sources.     

基于偏振模干涉的光纤光栅动态应变解调系统

基于保偏光纤中正交偏振模干涉,提出了一种简单、新颖的光纤光栅动态应变解调系统,并且通过实验证实了该方案的可行性。该解调系统光学核心部分仅由一段带有反射镜的高双折射光纤和一个光纤起偏器构成。实验中动态应变解调分辨率达到了 ,频率范围为0.1Hz~7.9kHz微纳振动幅度信号获得了保真拾取。实验表明,该系统适合宽频率范围、微纳幅度的动态应变检测,为光纤光栅传感提供了一种简单、经济、适用范围更广的解调方案。     

熊猫型单偏振光纤

熊猫型(PANDA)单偏振光纤(SPSM)主要用来制作光纤起偏器、光纤陀螺、光纤激光器和光纤传感器,较以往出现的其他种类的光纤起偏器具有明显的优势。我所采用打孔组装工艺来制作,通过在纤芯两侧对称置入应力施加单元引起高双折射,以及利用光纤芯区附近X和Y轴向折射率的不对称设计的方法,有效的改变了X和Y两个轴向的有效折射率,使得导模LP01中的两个简并模HE11X和HE11Y分别截止于不同的波长,通过将工作波长（1300 nm）设计选择在它们之间,使其中一个偏振模式HE11X导通,而另一个偏振模式HE11Y处于     

一种全自动调节的锁模光纤激光器

通过在非线性偏振旋转环形腔中引入一种全光纤化的角度可调的起偏器,简化了被动锁模光纤激光器的结构,通过调节环形腔内的光纤起偏器和1/4波片的角度就能够实现锁模脉冲的输出。基于此简化结构,引入基于单片机的触发反馈电路,控制偏振片和波片的旋转状态,实现了腔内锁模脉冲的自动调节输出,得到平均功率为8mW的、重复频率为5.6 MHz的全自动锁模脉冲稳态输出。     

Phase error bounds of fiber gyro with polarization-holding fiber

Phase error bounds for a fiber gyro with an imperfect polarizer are calculated assuming a broad-band source and high-birefringence fiber. The phase error and resulting zero-point drift is related to the polarization-holding parameterhof the fiber. Comparison of the theory with recent experimentally observed bias drift is made.     

耦合型微纳光纤偏振滤光器研究

微纳光纤偏振滤光器是光纤通信和传感系统的微型基本元件之一。利用超模耦合理论研究表明,当选择合适的耦合区长度和微纳光纤直径时,两平行紧贴微纳光纤构成的耦合器件可实现起偏效应,即将非偏振的输入光变为偏振光输出;理论设计分析给出了产生这种效应的几何参量值。实验研究了两根微纳光纤平行耦合时输出光偏振度(DOP)与耦合长度的关系,验证了起偏效应并制作了基于消逝场耦合的微纳光纤偏振滤光器。实验表明当微纳光纤偏振滤光器输入非偏振光时,在1545～1560nm波段耦合输出端光的偏振度达到了90%以上,实现了光束起偏;在此波段内某些波长的输出光消光比(LPER)可达到24dB以上,而其他波长处为椭圆偏振光或者圆偏振光,实现了分色起偏。此器件与检偏器组合可制成带通(阻)波长滤波器。     

Polarizer requirements for fiber gyroscopes with high-birefringence fiber and broad-band sources

Polarizer requirements for fiber-optic gyroscopes with high-birefringence fiber and broad-band sources are investigated theoretically by employing a model with a single coupling center between polarization modes. The phase bias offset due to a finite polarizer extinction ratio is greatly reduced by incoherent effects, and may be further reduced by using a depolarized source or by appropriate orientation of the polarizer transmission axis. Some experimental data is presented which supports the theoretical model.     

Pulse-train uniformity in optical fiber lasers passivelymode-locked by nonlinear polarization rotation

The generation of uniform soliton pulse trains by additive pulse mode locking has been experimentally demonstrated in a birefringent fiber laser with a passive polarizer. Numerical simulations of pulse propagation around such a fiber loop are presented which reveal that this mode-locking scheme does not result in strictly uniform pulse trains. Rather, the train of output pulses exhibits periodic fluctuations in intensity and polarization. A model for the pulse dynamics is developed which shows that these fluctuations depend on the strength of the fiber birefringence and the alignment of the polarizer with the fast- and slow-polarization axes of the fiber. It is also shown that increased uniformity of pulse trains is achieved with near alignment of the polarizer with the slow axis of the birefringence     

光纤环形激光器中锁模脉冲均匀性的理论分析和实验研究

从描述双折射光纤环形激光器动力学模型出发，模拟并分析了脉冲序列在非线性偏振旋转锁模光纤激光器环形腔内的演化过程，得出光纤快慢轴与起偏器之间的角度、以及双折射强度是影响锁模脉冲序列均匀性的重要因素，通过将普通单模光纤绕制成环产生应力双折射的方法进行了验证，并获得了中心波长1566．8nm、脉宽为1．5ps的稳定短脉冲序列。     

Wavelength tunability in a Nd-doped fiber laser with an intracavitypolarizer

When an intracavity polarizer is introduced into a Fabry-Perot Nd-doped fiber laser, wide wavelength tunability is achieved either by rotating the polarizer or by varying, the fiber birefringence with an in-line polarization controller. The intracavity polariser also produces considerable line-narrowing. A model based on birefringence dispersion is proposed     

Fiber loop polarizers using a fused taper coupler

All-fiber polarizers using a fused taper coupler are presented. The polarizers are fabricated by constructing a fiber loop joining the output ports of a fused taper coupler. Input light splits into two linearly polarized modes which are reflected and transmitted by the polarizers, respectively. The transmitted and the reflected lights become linearly polarized. The demonstrated polarizer shows an extinction ratio of -20.0 dB     

Magnetically tunable hollow-core anti-resonant fiber polarizer

An in-line high efficient polarizer, composed of magnetic-ionic-liquid-adorned(MIL-adorned) hollow-core anti-resonant fiber(HARF), is theoretically proposed and experimentally demonstrated. The protocol is based on the selective conversion of polarization mode into leaky mode and attenuates quickly in MIL and the polarizer is featured by the magnetically tunable polarization extinction ratio(PER) and the thermally controllable operation bandwidth.     

A simple angular alignment technique for apolarization-maintaining-fiber

Simple and accurate techniques for angular alignment of a polarization-maintaining-fiber (PMF) to a linearly polarized input beam are required for many optical-fiber applications. We consider an alignment technique wherein a short length of PMF undergoes a large temperature excursion and the output beam from the fiber is simply monitored by a linear polarizer and a power meter. Upon carefully considering the results for rotation angles near alignment, an accuracy better than 0.2° as well as a measurement of the fiber crosstalk are obtained     

基于偏振态变化时延估计的分布式光纤传感系统

提出一种基于偏振态（SOP）变化时延差估计的分布式光纤传感系统。本系统采用两个直流光信号在传感光纤中双向注入,振动会对正向和逆向光造成SOP变化,在各自的尾端利用起偏器检测SOP变化并转换为光强信息。两路信号间的时延差表明了振动的位置信息。对时延差形成的原因进行了理论分析,并阐明利用互相关算法计算该时延差并进行分布式传...     

Polarizing properties of a high index birefringent waveguide on topof a polished fiber coupler

The polarizing properties of a device made up of a high-index birefringent planar waveguide and a polished-type fiber coupler are analyzed. Approximate analytical formulas are derived for the width and the relative spacing of the TE and TM coupling resonances between the fiber and the waveguide. Experimental results are also shown and a practical in-line fiber polarizer based on this principle is demonstrated     

Left-handed and right-handed rotation double function circular polarizer

In order to gain circularly polarized light of left-handed and right-handed rotation by using a fixed device, a left-handed and right-handed rotation double function circular polarizer is designed with two λ/4 retarders and one polarizer, and its operating principle is analysed by matrix optical means. The result indicates that when the monochromatic light enters this circular polarizer in the positive direction and the negative direction,the emergent light should be circularly polarized light, of left-handed and right-handed rotation respectively. The testing system has been established to verify the above results.