Short pulse generation by higher order soliton-effect compression:effects of optical fiber characteristics

The effects of optical fiber characteristics on higher order soliton-effect pulse compression are investigated. We show that, for the compression of pulses with widths in the range of a few picoseconds or less, stimulated Raman scattering and third order dispersion result in severe degradation of the optimum compression ratio F_opt, while self-steepening has negligible effect. The initial pulse width dependence and the group velocity dispersion dependence of F_opt are investigated, leading to the identification of regimes that maximize F_opt and minimize the compressed pulse width. The effects of stimulated Raman scattering and third order dispersion on the quality of the compressed pulses are also investigated     

高阶效应对微结构光纤中超连续谱产生的影响

采用分布傅立叶方法求解了广义非线性薛定谔方程（GNSE）,数值模拟了飞秒激光脉冲在微结构光纤中的非线性传输和超连续谱的产生,详细分析了脉冲拉曼散射、自陡峭效应以及三阶色散对超连续光谱产生的影响。分析结果表明：超短脉冲在微结构光纤中传输时出现孤子自频移现象,同时也发现脉冲内拉曼散射和自相位调制的联合作用导致高阶孤子分裂,光谱得到极大展宽,在时域中出现两个滞后的拉曼孤子,三阶色散和自陡效应对光谱的形状影响较小,起着与脉冲内拉曼散射相反的作用,自陡效应比三阶色散效应对光脉冲的影响大一些。     

高阶模滤除法抑制蓝宝石光纤光栅反射谱带宽

蓝宝石光纤布拉格光栅在超高温恶劣环境下参数测试领域具有广泛的应用前景。但由于蓝宝石光纤本身的特性,不能支持单模传播,其反射谱带宽较宽,对测量精度造成了影响。利用光纤弯曲滤除高阶模的方法,使蓝宝石光纤实现基模传输。针对目前商用的150μm芯径蓝宝石光纤,基于耦合模理论,通过一系列数值计算,得出了能够满足基模传输且不损耗基模能量的弯曲半径,并得出了弯曲半径与布拉格中心波长的漂移特性。通过数值计算和优化设计,在一定弯曲半径下,反射谱带宽可减小到3 nm。这一结果大大提高了蓝宝石光纤布拉格光栅传感器的测量灵敏度,为蓝宝石光纤光栅在高精度、超高温测试场合的使用提供了方法和理论依据。     

Wavelength selective optical fiber couplers based on longitudinalFabry-Perot structures

A new approach for the development of wavelength selective optical fiber couplers is proposed. It is based on a standard polished fiber coupler in which an intermediate planar multilayer structure, which acts as a transversal optical filter, is included between the two fibers. The simplest multilayer structure, with interesting potential applications, is constituted by high refractive index single-layer Fabry-Perot filters. Experimental results for several single-layer Fabry-Perot filters, as well as a phenomenological model that provides accurate predictions about the wavelength selective coupling ratio, are presented     

Stability of femtosecond solitons in optical fibres influenced by optical attenuation and bandwidth limited gain

The stability of soliton pulses which undergo the Raman self-frequency shift in the presence of bandwidth limited amplification and loss is examined. General criteria for stable propagation are given which show this behaviour is sensitive to the shape of the gain profile and loss. In particular, stability can only be achieved in a narrow spectral region of the gain.<>     

Fused taper infrared optical fiber couplers in chalcogenide glass

We have fabricated low loss, high coupling ratio bidirectional optical couplers for infrared light using multimode step-index chalcogenide fiber. Using a fusion technique similar to that commonly employed with silica fibers, we have found a temperature regime where fusion can occur while interdiffusion of the core and cladding materials will not. The resultant device has a roughly 3:1 coupling ratio, less than 0.3 dB of excess insertion loss, and preserves the guided modes of the fiber intact     

分布式PT对称非线性耦合器中光纤孤子间的相互作用

为了在光纤孤子的应用装置中讨论孤子稳定性和相互作用,数值地研究了变系数耦合非线性薛定谔方程组。结果发现微孤子相互作用存在于具有周期分布的色散和非线性参量的PT对称非线性耦合器中。而且,在不同初始条件下,包括同相输入的两个或三个等幅孤子,及含反相二孤子输入的三孤子,都存在这样的微孤子相互作用。此外,还讨论了在有限初始扰动下微孤子相互作用的稳定性。结果表明,有限初始扰动不会影响微孤子相互作用的主要特征。     

Modal bandwidth enhancement in a plastic optical fiber by W-refractive index profile

A plastic optical fiber (POF) having a W-shaped refractive index profile (W-shaped POF) was prepared for the first time that had a possibility to realize a higher bit rate transmission than those of the conventional silica-based multimode fiber and graded index (GI) POF links. Since the W-shaped POF has a valley of the refractive index at the boundary of the core and cladding of the conventional graded-index (GI) POF, the group delay of higher order modes is strongly influenced, and the modal dispersion in the GI POF is compensated. By comparing the propagating mode properties of the W-shaped POF with those of the GI POF, we clarified theoretically and experimentally that the index valley has a remarkable modal dispersion compensation effect.     

Simultaneous suppression of third-order dispersion and sideband instability in single-channel optical fiber transmission by midway optical phase conjugation employing higher order dispersion management

In optical phase conjugation (OPC) systems, the third-order dispersion (TOD) of optical fibers and the nonlinear resonance at well-defined signal sideband frequencies called sideband instability (SI) mainly limit the transmission performance. We propose, for the first time, a scheme for simultaneous suppression of both TOD and SI in OPC systems using a periodic higher order dispersion-managed link consisting of standard single-mode fibers (SMFs) and reverse dispersion fibers (RDFs). Computer simulation results demonstrate the possibility of 200-Gb/s data transmission over 10 000 km in the higher order dispersion-managed OPC system, where the dispersion map is optimized by our system design strategies.     

Demonstration of optical fiber probes for high bandwidth thermalmeasurements in turbomachinery

Interferometric temperature sensors comprising a zinc selenide film on the end of a single-mode optical fiber have been incorporated into rugged probes for measurement of gas temperature fluctuations in aerospace turbomachinery test rigs. Two-wavelength illumination provides signals in quadrature for determination of optical phase change of the signal reflected from the film which is exposed to the gas flow. We present ensemble-averaged results showing 15 K amplitude gas temperature fluctuations up to 70 kHz with a resolution of 1 K     

FWM generation in higher order fiber dispersion managedtransmission line

Describes, in terms of fiber parameters, four-wave-mixing generation in a higher order fiber dispersion managed transmission line in which positive and negative dispersion fibers are used to manage both second- and third-order fiber dispersion. An analysis shows that the full-width at half-maximum interaction in dense wavelength-division-multiplexing systems can be reduced by properly setting the channel spacing to suit the dispersion allocation in the transmission line     

Investigation on bismuth-oxide photonic crystal fiber for optical parametric amplification

A hexagonal solid-core bismuth-oxide micro-structure fiber is developed to balance its dispersion and nonlinearity.This simulation and calculation results show that the bismuth-oxide photonic crystal fiber(Bi-PCF) has near zero dispersion around 1550 nm.Its dispersion slop in the communication wavelength range is also relatively flat.Moreover,both nonlinear coefficient and model field distribution are obtained.Compared with the experimental results by SiO2-PCF,it can be seen that the Bi-PCF shows excellent characteristics for the optical parametric amplification(OPA).     

Selective fused couplers consisting of a mismatched twin-core fiberand a standard optical fiber

This paper demonstrates a novel selective fused coupler consisting a mismatched twin-core fiber and an ordinary optical fiber. Selective coupling of over 99% has been achieved between the high NA core of the twin-core fiber and the ordinary optical fiber core with insertion loss as low as 0.04 dB. The coupler can be made easily on a standard fused coupler rig. We also studied the principle of the device. The device opens a variety of applications so far limited by the difficulty in simultaneous accessing the both cores of a mismatched twin-core fiber     

Signal light amplification by stimulated Raman scattering in anN-channel WDM optical fiber communication system

The use of forward and backward Raman amplification in an N -channel wavelength-division-multiplexing (WDM) optical-fiber communication system is analyzed. Analytical expressions for the signals, the pumps, and the amplified spontaneous scattered power (ASSP) are presented. The crosstalk among the signal channels is analyzed in terms of system parameters. It is found that the crosstalk is negligible while low pump power is used and becomes significant if high pump power is used. The signal-to-ASSP ratio can be improved by increasing pump power; however, the improvement is small when pump power is already high. A 300-km repeater spacing with more than 20-dB signal-to-ASSP ratio is calculated     

掺铒非线性光纤环镜中增益带宽对超短光孤子放大的影响

根据宽带脉冲的特点,建立了描述宽带脉冲放大的理论模型,并同时用数值方法研究了超短孤子在掺铒非线性光纤环镜中的放大.计算结果表明,当输入脉冲的频谱宽度和增益带宽相接近时,超短光孤子的波形和频谱产生畸变,放大效率降低,使得输出脉冲不再具有孤子特性.而这种影响可以通过优化不同增益带宽的ED-NALM中环的长度来消除.     

熔融拉锥型单模光纤光功率比耦合器的研制

本文由耦合波方程出发推导了熔融拉锥单模光纤耦合器的功率耦合比与拉伸长度的关系,并数值计算了光纤耦合器的光功率分配。实验上利用实验室现有的设备制作出2×2型、单窗口1×2型1550nm宽带耦合器,并完成了对制备出的光纤耦合器的光功率检测。通过理论与实验的比较得出熔融拉锥机制备的单模光纤光功率比耦合器的耦合曲线与理论上的耦合曲线基本一致,制备出的耦合器符合耦合器检验标准。     

Fundamental and higher order mode thresholds of DFB fiber lasers

Higher order modes are detrimental for distributed feedback (DFB) fiber lasers. The thresholds of these modes are calculated as functions of gain, loss, and various types of grating defects, like harmonic, linear, quadratic, and random chirp, and discrete phase errors. The higher order modes are particularly enhanced by high gain, quadratic chirp, and discrete phase errors close to the center of the grating     

Analytical calculation of pulse broadening in optical higher order PMD compensation

The system performances in second- and third-order polarization mode dispersion (PMD) compensations have been calculated analytically and a proper approach for the higher order PMD compensation has been investigated. The investigation has revealed that the frequency averaged higher order terms of the fiber link's PMD vector should be used as the coefficient vectors in emulating the frequency dependent compensation vector for higher order PMD compensation.