Dispersion-managed soliton interactions in optical fibers

We simulated dispersion-managed soliton propagation and interaction in optical fibers. The energy-enhancement factor, together with the time-bandwidth product and the stretching factor, were calculated as a function of the difference in absolute values of accumulated dispersion in the fiber spans. The interaction strength of the dispersion-managed solitons was found to depend on the stretching factor. When this factor is less than 1.5, the interaction is weaker than for ideal solitons. When it is more than 1.5, there is a strong interaction between the pulses, which constrains the energy enhancement for practical applications.     

Nonlinear soliton matching between optical fibers

In this Letter, we propose a generic nonlinear coupling coefficient, η(NL)2=η|γ/β?|(fiber2)/|γ/β?|(fiber1), which gives a quantitative measure for the efficiency of nonlinear matching of optical fibers by describing how a fundamental soliton couples from one fiber into another. Specifically, we use η(NL) to demonstrate a significant soliton self-frequency shift of a fundamental soliton, and we show that nonlinear matching can take precedence over linear mode matching. The nonlinear coupling coefficient depends on both the dispersion (β?) and nonlinearity (γ), as well as on the power coupling efficiency η. Being generic, η(NL) enables engineering of general waveguide systems, e.g., for optimized Raman redshift or supercontinuum generation.     

Multimaterial preform coextrusion for robust chalcogenide optical fibers and tapers

The development of robust infrared fibers is crucial for harnessing the capabilities of new mid-infrared lasers. We present a novel approach to the fabrication of chalcogenide glass fiber preforms: one-step multimaterial extrusion. The preform consists of a glass core and cladding surrounded by a built-in, thermally compatible, polymer jacket for mechanical support. Using this approach we extrude several preform structures and draw them into robust composite fibers. Furthermore, the polymer cladding allows us to produce robust tapers with submicrometer core diameter.     

Chirp-controlled soliton fission in tapered optical fibers

Manipulation of the input pulse chirp during supercontinuum generation in tapered fibers provides precise control of the soliton fission process taking place in the taper waist. Simulations and experiments demonstrate that controlling this pre-chirp by a pulse shaper can be applied to compensate for deleterious effects due to untapered fiber pigtails. Temporal and cross-correlation frequency resolved measurements are utilized to show, that the control of the soliton fission dynamics can be obtained by manipulating the input pulse chirp through the imposition of a quadratic spectral phase. PACS 42.65.Wi; 42.65.Tg; 42.81.Qb; 42.81.DP     

光纤损耗对皮秒脉冲孤子效应压缩的影响

在计及常规光纤损耗的前提下，通过数值求解求解修正的非线性薛定谔方程，全面地计算和分析了损耗对皮秒脉冲在单模光纤中孤子效应压缩过程的影响。结果表明，与不计及损耗时相比，损耗一方面导致脉冲压缩比，压缩后的脉冲峰值功率和脉冲压缩质量的下降，另一方面还导致所选用的最佳光纤度的增加。进一步研究表明，损耗对脉冲压缩的影响程度还与输入脉冲的峰值功率和脉宽有关。     

新世纪的非线笥光纤光孤子通信

全面地论述了非线性光纤光孤子通信的发展以及跨世纪发展的光明前景。     

Compact optical fiber curvature sensor based on concatenating two tapers

A low-loss, compact, and highly sensitive optical fiber curvature sensor is presented. The device consists of two identical low-loss fused fiber tapers in tandem separated by a distance L. When the optical fiber is kept straight and fixed, no interference pattern appears in the transmitted spectrum. However, when the device is bent, the symmetry of the straight taper is lost and the first taper couples light into the cladding modes. In the second taper, a fraction of the total light guided by the cladding modes will be coupled back to the fundamental mode, producing an interference pattern in the transmitted spectrum. As the fiber device is bent, visibility of the interference fringes grows, reaching values close to 1. The dynamic range of the device can be tailored by the proper selection of taper diameter and separation between tapers. The effects of temperature and refractive index of the external medium on the response of the curvature sensor is also discussed.     

Dispersion-managed soliton in optical fibers with zero average dispersion

A dispersion-managed optical system with stepwise periodic variation of dispersion is studied in the framework of a path-averaged Gabitov-Turitsyn equation. The soliton solution is obtained by means of iterating the path-averaged equation. The dependence of soliton parameters on dispersion map strength is investigated, together with the oscillating tails of the soliton.     

光孤子脉冲在光纤放大器中的传播

本文建立了包括增益色散,受激喇曼散射,双光子吸收效应的理论模型,讨论了光孤子脉冲在光纤放大器中的传播.数值计算结果表明:在反常色散范围内,光孤子的放大是不稳定的.增益色散导致光脉冲对称分裂,而受激喇曼散射则导致不对称的分裂.在增益色散和受激喇曼散射的共同作用下可获得新的时域和频域特征.有限带宽的放大能抑制受激喇曼散射引起的自频移.本文对有啁啾的光孤子脉冲的放大也进行了分析.     

Some types of dark soliton interactions in inhomogeneous optical fibers

Dark solitons are the subject of intense theoretical and experimental studies in nonlinear optics due to their unique characteristics compared with bright solitons. In this paper, the variable coefficient high-order nonlinear Schrödinger equation in the inhomogeneous optical fiber is investigated. Via the Hirota bilinear method and symbolic computation, the analytic dark two-soliton solutions are obtained. With the suitable choices of functions and coefficients for the obtained dark two-soliton solutions, some new phenomena are presented for the first time. The influences on phases and amplitudes of soliton interactions are detailed analyzed. Moreover, sets of double-triangle structures and methods of changing the propagation direction of dark solitons are introduced. Finally, by choosing suitable functions of the fourth-order dispersion parameter, the arch-structure and M-structure interactions are revealed. Results may be potentially useful in designing all-optical switches and optical fibers.     

中红外超连续谱在氟化物光纤中的产生

为获得高功率全光纤中红外超连续谱,采用自制的掺Er锁模光纤激光器作为种子源,激光经过两级放大至1.67 W,泵浦氟化物光纤,获得光谱覆盖1000~2400 nm的超连续光谱;光谱宽度随着泵浦功率的增加而展宽,当输出功率达到1.21 W时,转换效率为72%,并且产生的超连续谱被强烈的调制,在多个波长点处谱功率密度调制到0 mW/nm,但调制波长与泵浦功率无关。     

Approxiamation theory for unequal amplitude soliton pairs in nonliear optical fibers

The equivalent-particle approach is used to investigate the interaction of two unequal-amplitude solitons propagating in nonlinear fibers by regarding the interaction as a perturbation. The Newtonian equations for the motion of solitons are given. Results show that the interaction of an unequal-amplitude soliton pair can be approximated as the product of a local interaction factor dependent on the propagation distance and a nonlocal interaction factor independent of the propagation distance. The local factor forces soliton interaction to alternate between the attractive and the repulsive, and, on a large scale, the average of this character markedly reduces the interaction of the unequal-amplitude solitons.     

High-quality sub-100-fs optical pulse generation by fiber-optic soliton compression of gain-switched distributed-feedback laser-diode pulses in conjunction with nonlinear optical fiber loops

We report our investigations of a new and simpler femtosecond fiber-optic soliton compressor for chirp-compensated gain-switched diode-laser pulses and of pedestal suppression by a compound fiber loop mirror (CFLM) and nonlinear-optical loop mirrors (NOLM's), both of which are designed for sub-100-fs pulse generation of high quality. The soliton compressor, composed of a 21.1-m-long steplike dispersion profiled fiber, exhibited 44-fs pulses and a compression ratio of approximately 60. Pedestals of 100-fs soliton pulses were suppressed successfully (>20 dB) by the CFLM and the NOLM's. In particular, 63-fs pedestal-free sech(2) pulses were obtained by NOLM propagation.     

Stimulated Brillouin scattering in dispersion-decreasing fiber with ultrahigh-speed femtosecond soliton pulse compression

We report that stimulated Brillouin scattering (SBS) in a dispersion-decreasing fiber (DDF) is particularly disadvantageous with ultrahigh-speed femtosecond soliton compression that exceeds 40 GHz. It is important to note that the increase in the longitudinal mode power of a soliton is proportional to the square of the repetition rate. The SBS threshold is determined by the dispersion-decreasing rate of the DDF, rather than its fiber loss. We suppressed the SBS by applying 30-MHz frequency modulation to a mode-locked fiber laser and successfully obtained a stable 40-GHz, 100-fs pulse train.     

Initial stochastic modulation and break up of soliton bound states in optical fibers

We analyzed the influence of the initial phase stochastic modulations of high power optical pulses on their propagation in optical fiber. Our numerical results are compared with those of Cavalcanti S.B., Agrawal G.P.: Phys. Rev. A 51, 4086–4092 (1995), Fattakhov A.M., Chirkin A.S.: Kvantovaya Elektronka 11, 1989 (1983), Kvantovaya Elektronka 11, 2349 (1984), Maimistov A.I., Manykin B.A., Skliyarov Y.M.: Kvantovaya Elektronka 13, 2243–2248 (1986). Break up of soliton bound states due to initial phase stochastic modulations is observed.     

Radio emission of an optical soliton propagating in a ring fiber

Considered are emission processes occuring in the course of propagation of an optical soliton along a ring fiber. The spatial and temporal characteristics of radiation are calculated. It is demonstrated that conditions are possible in which radiation becomes observable.     

Experimental observation of orthogonally polarized time-delayed optical soliton trapping in birefringent fibers

Propagation of two orthogonally polarized time-delayed optical solitons in low-birefringence optical fiber is studied experimentally. We demonstrate soliton trapping and collisions and also the ability to control the separation and shape of soliton pulses by varying the power at the input of the fiber.     

Femtosecond soliton generation induced by intrapulse stimulated Raman scattering in optical fibers

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