Optical frequency shifter using linearly birefringent monomode fibre

An optical frequency shifter has been constructed which uses travelling acoustic flexure waves induced on a single linearly birefringent monomode fibre to produce mode coupling between the two orthogonal polarisation eigenmodes. The output of the frequency shifter is examined using a heterodyne interferometer. The measured efficiency was ?2% at a shift frequency of 491 kHz.     

Highly birefringent and monomode GaAlAs-GaAs planar optical waveguide

A novel optical waveguide exhibiting a layered core region is proposed. Owing to the original design of the core stack and form birefringence in the multilayer, a waveguide supporting both TE and TM lowest-order modes with high confinement has been obtained. It has been designed, fabricated, and characterized and presents a modal birefringence greater than 0.01, which is in good agreement with the calculated values.     

Signal transmission by optical solitons in monomode fiber

A transmission rate of ≃1 Tbits/sec (≃0.1 Tbits/s) per 30 km can be achieved using envelope solitons with peak power of ≃10 W (≃10 mW) in a monomode optical fiber, respectively. Unlike the linear pulse in which the bit rate is limited by the group dispersion, the bit rate of soliton transmission is limited by the fiber loss and the input power. Conditions for achieving optimum transmission rate using solitons are theoretically obtained including the effects of fiber loss and second order group dispersion.     

弱双折射光导纤维内的非线性光传输

光在光纤波导内传输过程中，由于光能量非常集中，光与物质作用距离长，因而会产生一系列的非线性效应。例如人们对受激拉曼散射（SRS）和受激布里渊散射（SBS）作了大量的研究。     

Interferometric chromatic dispersion measurements on short lengthsof monomode optical fiber

Chromatic dispersion measurements on short lengths of monomode optical fiber by the technique of `white light' interferometry are presented. Improved optoelectronic signal processing and rigorous data reduction techniques have resulted in a temporal resolution of ⩾7×10^-5 ps·nm^-1 in a 1-m length of fiber, equivalent to 0.06% resolution in the measurement technique. This is equivalent to a first-order chromatic dispersion coefficient ( D(λ)) resolution of 0.07 ps·nm^-1·^-1. The second-order chromatic dispersion coefficient (S(λ)) resolution was 0.02 ps·nm^-2·nm^-1. Experimental results of D(λ) and S(λ) for three different fibers are compared to theoretical calculation of material and waveguide dispersion     

Electric-discharge sensor utilizing fluorescent optical fiber

A fluorescent optical fiber made of Na₂O-CaO-5SiO₂ glass doped with Sm³⁺ which absorbs light and then emits a longer-wavelength light is discussed. The sensor can capture light from a light source even though its aperture is not directed toward the source. This property is useful for detecting light from an unfixed light source, such as in cases of electric discharge. An electric-discharge sensor utilizing this fiber has been constructed and successfully applied to the detection of electric discharges in a test device similar to a section of a gas-insulated substation (GIS)     

高双折射单模光纤温度传感器

1 引言 偏振干涉型光纤温度计的灵敏度介于干涉型和强度型之间。典型的干涉型光纤温度传感器是以光纤耦合器为核心,构成Mach-Zehnder的一类干涉仪,它是以两根光纤分别作为干涉仪的测量臂和参考臂。虽然灵敏度高,但由于外界环境因素对参考臂的干扰极为敏感,以致在一般条件下,难以正常工作。文献[2]则以一根高双折射光纤中正交偏振模HE_(11)对外界因素有不同相移,使这两个模式的光发生干涉,从而能有效地克服外界因素的干扰。本文利用时间相     

熊猫光纤热双折射效应光纤偏振控制器研究

根据熊猫光纤热双折射效应原理.通过电热控制的方法实验研究其热双折射效应,提出并实验演示了基于熊猫光纤热双折射效应的光纤偏振控制器.研究了熊猫光纤热双折射效应的温度灵敏度和电热控的特点.将两段熊猫光纤按偏振轴相互偏离一定角度熔接后,两段熊猫光纤的电热控制将分别在邦加球上形成相交并互相成一定夹角的两个截交线圆,组合两段熊猫光纤的电热控制可实现偏振态在邦加球上的部分覆盖.根据熊猫光纤热双折射效应的特点,提出并实验演示了由三段熊猫光纤组成的电热控光纤偏振控制器,它可在实验上实现任意偏振态的扫描控制.     

Observation of ultrafast nonlinear polarization switching inducedby polarization instability in a birefringent fiber rocking filter

Ultrafast all-optical switching between two orthogonal linear polarizations in a periodically twisted fiber filter is discussed. The dependence of the switching characteristics on the input power and operating wavelength is considered     

High-performance optical fiber polarizers based on long-period gratings in birefringent optical fibers

We have demonstrated the feasibility of achieving high-performance fiber polarizers (insertion loss <0.5 dB, extinction ratio >30 dB), based on polarization mode dispersion in a long-period grating. Chirped operation with 100-nm bandwidth has also been achieved, showing the possibility of a broad-band device.     

Analysis on state of polarization of stimulated Brillouinscattering in an optical fiber ring-resonator

As a basic study of a Brillouin fiber-optic gyro, the state of polarization of stimulated Brillouin scattering in an optical fiber ring-resonator is analyzed. A high-birefringent fiber ring-resonator with 90° polarization axis rotation at the splice is considered as a candidate to have a stable lasing. It has two special states of polarization as the lasing modes, namely the polarization lateral modes. The lasing frequencies, namely the longitudinal modes for one state are fixed just in the middle point between the two neighboring lasing frequencies for the other in this resonator. This means that the stable single mode lasing may be obtained. The lasing threshold, the alternation of the lasing modes are discussed both by the simplified theory and the strict theory     

A broad-band single polarization optical fiber

The authors report on a single-mode optical fiber that transmits one and only one polarization state of the fundamental mode over a broad wavelength band (13%). The good broadband performance is attributed to the fiber's refractive-index profile, which mathematically allows only one polarization state to cutoff. The authors discuss general design principles and show that the mode field diameter is a qualitative indicator of the fiber's performance. The fiber's guided polarization state is similar to the fundamental mode of a step-index fiber in its low attenuation, 5.5 dB/km, and small mode diameter, 5.8 μm (both measurements at 840 nm). Most important, the fiber shows a broad single polarization band, 13%, a feature well described by the change in mode field diameter with wavelength of an ideal, circularly symmetry, W -profile fiber     

Anisotropic polarization maintaining optical fiber ring resonators

Suppression of the polarization drift of optical fiber ring resonators is investigated both theoretically and experimentally by employing anisotropy in a polarization maintaining fiber ring. A general analytic expression for the transmission of the device is derived allowing the fiber modes to exhibit any combination of polarization crosstalk, differential loss or differential coupling. The analysis shows that a moderate level of ring anisotropy, such as that of 10 dB in line polarizer or polarization selective coupler, is sufficient to greatly suppress the drift of the eigenstates of polarization (ESOPs), finesse and resonant point, restoring the device's suitability for most practical applications. An inevitable consequence of introducing ring anisotropy is the loss of orthogonality of the ESOPs. This effect limits the anticipated benefit in high sensitivity applications. A practical anisotropic PMRR is demonstrated by inserting a thin film of nematic liquid crystal between the two halves of the polished coupler of the ring. This resonator demonstrates a polarization response immune to environmental perturbations     

Suppression of polarization switching in birefringent antiresonant reflecting optical waveguide vertical-cavity surface-emitting lasers

Influence of birefringence on the multimode operation of antiresonant reflecting optical waveguide (ARROW) vertical-cavity surface-emitting lasers (VCSELs) is analyzed. It can be shown that polarization switching is mainly due to thermal lensing effects. Hence, a new design rule is proposed to optimize the dimensions of ARROW for the suppression of polarization switching. Using the optimized design, the maximum single-polarization output power of VCSELs can be tripled. In addition, it is shown that the performance of the optimized ARROW VCSELs will not be deteriorated by the uncertainty of birefringence.     

偏振模色散仿真器特性研究

光纤通信线路的偏振模色散已成为高速、长距离光纤通信系统发展的主要障碍之一 ,其特性、测量以及补偿方法的研究成为目前光纤通信研究热点之一。偏振模色散仿真器 ,用于仿真传输链路的偏振模色散特性 ,不仅可用于偏振模色散补偿器 ,也可用于高速长距离光纤通信系统的规划设计等。本文分析了光纤偏振模色散仿真器的研究现状 ,归纳总结了现有偏振模色散仿真器的设计原理和结构特征 ,并用蒙特卡罗法对常用的偏振模色散仿真器的特性进行了数值模拟     

Degenerate-cross-phase modulation of femtosecond laser pulses in a birefringent single-mode optical fiber

Degenerate-cross-phase modulation has been observed for femtosecond laser pulses propagating through a short birefringent single-mode optical fiber. The difference in the spectral broadening of the two output polarization components of a single laser pulse was attributed to the combination of self-phase modulation and degenerate-cross-phase modulation processes in the optical fiber. Theoretical simulations based on the solutions of the two coupled nonlinear Schrodinger equations are in good agreement with the measured results.     

Phase noise and polarization state insensitive optical coherentsystems

The authors present three different schemes that allow compensation of phase noise and polarisation state change by sending a reference channel that is suitably frequency shifted by using polarization modulation together with Stokes parameters detection or computing and inverting the Jones matrix that describes the fiber polarization state transformation. As a conclusion, some comparisons are made among different approaches in order to show how different systems can be tailored to different requirements both in point-to-point and in multipoint networks     

保偏光纤的偏振特性分析

在惯性制导用光纤陀螺中,用保偏光纤绕制的Sagnac环圈是其中的关键器件.文章首先介绍了保偏光纤中偏振光传输的概念与定义;然后,对保偏光纤偏振特性的表征参数:拍长、偏振串音和偏振保持参数(h)进行了详细的介绍;最后,分析讨论了h参数与偏振串音的关系.     

Influence of birefringence dispersion on a distributed stress sensor using birefringent optical fiber

Distributed stress sensor with a white-light scanning interferometer is used to detect stress distribution by analyzing polarization mode coupling caused by forces exerted on PMFs (polarization maintaining fibers). In measurement of polarization coupling, the birefringence in sensing fiber is usually considered to be wavelength independent. Sensitivity and spatial resolution of the distributed stress sensor are constant for a given optical source spectrum. In practical measurement, however, the birefringence in PMFs is related with optical wavelength. In other words, birefringence dispersion exists in PMFs. Due to birefringence dispersion, the relationship between stress and coupling strength varies with different positions of external forces, and spatial resolution of the distributed stress sensor descends obviously with transmitted distance. In this paper, influences of external-force positions and optical source spectrum on distributed stress sensor are analyzed in consideration of birefringence dispersion and validated with experiments. A method for compensating birefringence dispersion in the sensing system is proposed in the end.