Ultrahigh-speed long-distance TDM and WDM soliton transmissiontechnologies

Recent progress on time-division multiplexed (TDM) and wavelength-division multiplexed (WDM) soliton transmission is described, in which dispersion management (DM) plays an important role in increasing the power margin and the dispersion tolerance. The characteristics of the DM soliton are compared with those of return-to-zero (RZ) and nonreturn-to-zero (NRZ) pulses. With a small dispersion swing, the system can still be described as an average soliton with a nonlinear Schrodinger equation (NLSE), whereas with a large dispersion swing, the soliton-like steady-state pulse becomes a chirped Gaussian pulse, in which the master equation is closer to a linear Schrodinger equation (LSE) with a parabolic potential well. An in-line modulation scheme up to 80 Gb/s per channel and its two-channel WDM transmission over 10000 km are described. A 640-Gb/s (40 Gb/s×16 channels) WDM soliton transmission over 1000 km is also reported with a DM single-mode fiber, without the use of in-line modulation. Finally, dark soliton transmission at 10 Gb/s over 1000 km is described as a different nonlinear pulse application     

Wavelength tunable 10-GHz 3-ps pulse source using a dispersion decreasing fiber-based nonlinear optical loop mirror

We experimentally demonstrate the use of a dispersion decreasing fiber (DDF)-based nonlinear optical loop mirror (NOLM) for the generation of wavelength tunable soliton-like pulses at a repetition rate of 10 GHz. We compress /spl sim/12-ps Gaussian pulses from an electro-absorption modulator (EAM) (followed by 125 m of DCF for preliminary linear dispersion compensation) into 3-ps pedestal-free pulses using both high-order soliton compression and nonlinear switching effects within an 8.5-km DDF-based loop mirror. The output pulses from the DDF-based NOLM show considerable pedestal reduction compared to those obtained by directly compressing the EAM seed pulses via a single passage through the DDF. Wavelength tuning of the compressed pulses over a /spl sim/15-nm bandwidth (from 1541 to 1556 nm) is demonstrated without a significant increase in pulse duration or degradation in pulse quality.     

Influences of polarization-mode dispersion on soliton transmissionsystems

In soliton transmission systems with polarization-mode dispersion (PMD), random birefringence causes solitons to generate dispersive waves, which degrade soliton transmission systems in two aspects. First, the dispersive waves cause solitons to continuously lose energy, thus induce pulse broadening. Second, the dispersive waves interact with other soliton pulses and cause distortion of a sequence of soliton pulses. Both of these effects induce performance degradation of soliton transmission systems. We study these effects of PMD on both conventional and dispersion-managed (DM) soliton transmission systems. We show that, for conventional soliton systems, although single pulse has robustness to PMD, the interplay between the dispersive waves and solitons would seriously distort a sequence of pulses and make soliton systems worse than linear systems if all other transmission impairments are neglected. We also show that DM solitons are more robust to PMD than both conventional solitons and linear systems due to the enhanced nonlinearity and less sensitivity of DM solitons to perturbations. We further point out that soliton collision-induced polarization scattering causes additional timing jitter and system performance penalty in WDM soliton systems     

Systematic construction of vector solitons

We present a simple but powerful method for constructing multisolitons; of the integrable Manakov (coupled nonlinear Schrodinger) equation. Our method is essentially equivalent to the inverse scattering method (ISM) with the full strength generality but without the mathematical rigor of the ISM. This makes our method appropriate for practical purposes. A closed form of matrix determinant for the N-soliton solution in a nonvanishing background is found in this way. We work out explicitly the two dark vector soliton and the three bright vector soliton cases and demonstrate their novel behaviors     

Introduction of electrostriction-induced acoustic interaction inmodeling of high-capacity long-haul transmission systems

We present a method to implement an electrostriction-induced acoustic effect in the nonlinear Schrodinger equation (NLSE) and to validate it from a system point of view in particular, by comparison with experimental results. Special focus is devoted to acoustic cross effects between channels in wavelength-division multiplexing (WDM) transmission. The model is then applied to different realistic single-channel 40-Gb/s soliton systems in the presence of dispersion management or in-line optical regeneration to evaluate induced penalties     

The averaging method for finding exactly periodicdispersion-managed solitons

A numerical averaging method for finding exactly periodic solutions [dispersion-managed (DM) solitons] of the nonlinear Schrodinger equation with dispersion management is described. Variations of the method for finding solutions of fixed energy and fixed pulsewidth are discussed, and the effects of including fiber loss are considered. The generation of resonant sidebands due to phase matching between the DM soliton and the background is described for average anomalous, zero, and normal dispersion     

基于潮流灵敏度的IST安装位置选择

新型“SEN Transfomer”(IST)是一种由三相双绕组变压器和有载调压开关组成的电磁式统一潮流控制器,较ST具有更灵活的潮流调控能力与更大的潮流调控范围。文中详细介绍了IST的拓扑结构及基本工作原理,推导了IST的功率注入模型。引入线路有功潮流性能指数,根据IST基本选址原则及计算得到的潮流灵敏度系数,以提高系统有功潮流调节能力为目的,对IST的安装位置进行了选择。在IEEE 14节点系统中对所提出的方法进行了验证,结果表明在该方法计算得到的支路上安装IST后,系统的有功潮流分布得到了明显的改善。     

Widely wavelength-tunable ultrashort pulse generation usingpolarization maintaining optical fibers

Characteristics of widely wavelength tunable ultrashort pulse generation using several types of polarization maintaining fibers have been experimentally analyzed. Using the diameter reduced type of polarization maintaining fibers, the wavelength tunable soliton pulse is generated from 1.56 to 2.03 μm. It is confirmed that the almost transform-limited 340-fs soliton pulse is generated at a wavelength of around 2 μm using a frequency-resolved optical gating method. When low-birefringence fibers are used, it is observed that the orthogonally polarized small pulse spectrum is trapped by the soliton pulse and is also shifted toward the longer wavelength side in the process of soliton self-frequency shift. The wavelength of the orthogonally polarized pulse spectrum is 40-50 nm longer than that of the soliton pulse, and the birefringence of the fiber is compensated by the chromatic dispersion. Finally, a polarization maintaining highly nonlinear dispersion-shifted fiber is used as the sample fiber. When the fiber input power is low, the wavelength-tunable soliton and anti-Stokes pulses are generated. As the fiber input power is increased, the pulse spectra are gradually overlapped and the 1.1-2.1 μm widely broadened supercontinuum spectra are generated by only 520 pJ pulse energy     

A simple design of a highly tolerable dispersion managed soliton system for trans-oceanic distance transmission

Contents  We present a design for a dispersion managed (DM) soliton system, which is based on two primary parameters; the dispersion compensation period (DCP), which is defined by the number of DSF spans between dispersion compensation fiber, and pulse width. We designed the optimum value of these two parameters to achieve the widest system margins for both repeater output power and signal wavelength for trans-oceanic distance transmission. We checked this analysis by experiments for both 10 and 20 Gb/s DM soliton systems having 53 km repeater spacing. Experimental results confirm the validity of proposed system design. Received: 16 January 2001     

Coupled resonator optical waveguides

Properties of the recently introduced family of coupled resonator optical waveguides (CROWs) are reviewed, particularly with reference to CROWs designed as planar waveguides in two-dimensional photonic crystal slabs to enhance nonlinear interactions and develop novel all-optical information processing devices. Topics covered include: pulse propagation both in the nondispersive approximation and to all orders of dispersion, and the coupled mode theory of nonlinear optics with pulses in CROWs and its applications to second-harmonic generation and wave coupling via field-induced refractive-index gratings. We also review recent experimental progress in the fabrication and characterization of CROWs, and applications of the CROW concept to fiber gratings and microwave waveguides     

Pulse generation for soliton systems using lithium niobatemodulators

We describe the principle of operation and performance of several soliton pulse sources and also a complete soliton transmitter based on lithium niobate modulators. Subsystems based on lithium niobate modulators are attractive because the modulators are now commercially available, qualified for system use, can operate up to very high speeds, and can operate over a wide wavelength range. The pulse sources we describe are based on two techniques. The first is the chirped pulse compression technique in which one or two sinusoidally driven modulators generate frequency chirped pulses that are subsequently compressed to the desired width using dispersion in a fiber. In the second technique, sinusoidally driven modulators are cascaded serially to form pulses. Using these techniques we produced nearly transform-limited pulses at repetition rates up to 15 GHz with a FWHM pulsewidths from 10-33% of the pulse period. A complete soliton transmitter using a single modulator to simultaneously generate optical pulses and encode data is also discussed. The performance of this compact transmitter in a 2.5-Gb/s soliton system experiment is comparable to other more common soliton transmitters     

Toward single-cycle laser systems

Few-cycle pulse generation based on Ti:sapphire, Cr:forsterite, and Cr:YAG gain media is reviewed. The dynamics of these laser systems is well understood in terms of soliton and dispersion managed soliton formation stabilized by artificial saturable absorber action provided by Kerr-lens modelocking. These systems generate 5-, 14-, and 20-fs pulses with spectral coverages of 600-1150, 1100-1600, and 1200-1500 nm, respectively. The design of dispersion compensating laser optics providing high reflectivity and prismless operation over this bandwidth is discussed. A novel active synchronization scheme based on balanced optical cross correlation, the equivalent to balanced microwave detection, for synchronization of independently mode-locked lasers is introduced. Its use in synchronizing an octave-spanning Ti:sapphire laser and a 30-fs Cr:forsterite laser yields 300 attoseconds timing jitter measured from 10 mHz to 2.3 MHz. The spectral overlap between the two lasers is large enough to enable direct detection of the difference in the carrier-envelope offset frequency between the two lasers. These are the most important steps in the synthesis of single-cycle optical pulses with spectra spanning 600-1600 nm.     

用动态留数法确定非线性控制器的最佳配置地点

提出了一种动态留数法,对含有分散非线性控制器的多机电力系统的主导模态进行动态扫描,根据分散非线性控制器安装前后系统主导模态的变化来确定系统中非线性控制器的最佳配置地点。当在线应用本方法时,建议构造一种基于多Agent的电力系统智能非线性控制的体系结构。它是一个由协调层和执行层组成的多Agent系统(Multi-AgentSystem),协调层Agent采用“动态留数”法确定系统中非线性控制器的最佳配置地点,执行层Agent负责非线性控制器参数的优化和控制器的切换。一个10机系统的离线仿真结果表明,这种方法能有效地消除不稳定零动态特性,提高多机电力系统的暂态稳定性。     

Efficient wavelength selective soliton switching using fibergratings in single and cascaded nonlinear optical loop mirrors

The soliton switching performance of the nonlinear optical loop mirror (NOLM) with inserted fiber Bragg grating is examined numerically in this paper. The relationships between various grating designs to the self-switching characteristics of the device are presented, including cases where low switching powers and rapid switching transitions are observed. Particular attention is paid to the bandpass nonlinear switching behavior of the NOLM, introduced with the inclusion of the grating. This analysis is extended to consider a novel cascaded loop configuration, in which the gratings in each loop are tuned to a different wavelength. A three-channel simulation of a two-loop cascade is presented with a discussion on the suitability of the NOLM device to wavelength-division-multiplexing (WDM) applications     

Novel linear and nonlinear optical properties of electromagnetically induced transparency systems

We describe some interesting linear and nonlinear optical properties of three-level electromagnetically induced transparency (EIT) systems, such as absorption reduction, sharp dispersion change, and enhanced Kerr nonlinearity. These novel optical properties are very useful in enhancing efficient nonlinear optical processes, which can find applications in optoelectronic devices. We present some experiments done in our group in the past few years with three-level atomic systems, especially more recent experiments with EIT medium inside an optical cavity.     

Parametric amplification and self-compression of ultrashort tunablepulses

Using a 40-fs Ti:sapphire pump laser, we produced 20-fs infrared pulses in a β-barium borate (BaB₂O₄) optical parametric amplifier without any external dispersion compensation. These results are in good agreement with a novel semi-analytical computer simulation. We also demonstrate that cascading of second-order nonlinear effects yields simultaneous production of ultrashort visible pulses from a near-infrared (NIR) pump     

Soliton mode-locking with saturable absorbers

We investigate ultrashort pulse generation based on the fundamental soliton generation that is stabilized by a saturable absorber. The case of an absorber with a recovery time much longer than the pulsewidth of the generated soliton is investigated in detail. Based on soliton perturbation theory we derive equations for the soliton variables and the continuum generated in a mode-locked laser. Analytic criteria for the transition from stable to unstable soliton generation are derived. The results demonstrate the possibility of ultrashort pulse generation by a slow saturable absorber only. The theoretical results are compared with experiments. We generate pulses as short as 13 fs using only semiconductor saturable absorbers     

Analysis and design equations for phase matching using Bragg reflector waveguides

In this paper, we introduce and analyze a novel wave-guide design to provide phase matching for nonlinear optical processes. Phase matching is achieved by designing the structure to guide the fundamental frequency by total internal reflection and the second harmonic (SH) frequency by transverse Bragg reflection. By forcing the SH mode to operate in the middle of the Bragg stopband, we solve for the waveguide dimensions for arbitrary waveguide materials, given the material dispersion between the fundamental and SH frequencies. Using GaAs-AlGaAs as an example, we analytically investigate and quantify properties such as nonlinear coupling efficiency, bandwidth, tunability, and limitations due to dispersion. The technique shows tremendous promise when compared to alternate technologies, where it is particularly attractive as an effective means to obtain ultralow-loss nonlinear optical elements for monolithic integration with coherent light sources and other active devices.     

Multichannel soliton transmission and pulse shepherding inbit-parallel-wavelength optical fiber links

We study basic principles of the bit-parallel-wavelength (BPW) pulse transmission in multichannel single-mode optical fiber links for high-performance computer networks. We develop a theory of the pulse shepherding effect that allows simultaneous propagation of pulses in parallel bit slots by binding them into a multicomponent BPW soliton. We describe families of the BPW solitons and bifurcation cascades in a system of N incoherently coupled nonlinear Schrodinger equations that model the multichannel multiwavelength transmission in a single-mode optical fiber. We demonstrate high robustness of the composite BPW solitons, due to their underlying linear stability, to a moderate pulse walkoff     

Dynamics of nonstationary return-to-zero pulses in dispersion-managed systems

We describe an analytical framework for return-to-zero (RZ) propagation in dispersion-managed fiber systems. The pulses may generally not follow the same periodicity as that of the dispersion map (i.e., nonstationary evolution), which can complicate the design and monitoring of such systems. We show that a phase-plane representation of pulses is useful in identifying as well as predicting the salient features of this multiscale and nonlinear evolutionary behavior. Numerical calculations of RZ pulse-train propagation over 4000 km are carried out to demonstrate the correspondence of theory and simulation.