Three-wavelength generation from cascaded wavelength conversion in monolithic periodically poled lithium niobate

Tunable coherent emission is generated in a single-pass, cascaded wavelength conversion process from mode-locked laser-pumped monolithic periodically poled lithium niobate（PPLN）. Three ranges of wavelength, including visible output from 628 nm to 639 nm, near-infrared output from 797 nm to 816 nm, and mid-infrared output from 3167 nm to 3459 nm,were obtained from the monolithic PPLN, which consists of a 10-mm section for 532-nm-pumped optical parametric generation（OPG） and a 7-mm section for 1064-nm-pumped sum frequency generation（SFG）. A pump-to-signal conversion efficiency of 23.4% for OPG at 50°C and a quantum efficiency of 26.2% for SFG at 200°C were obtained.

Towards 640 Gbit/s wavelength conversion based on nonlinear polarization rotation in a semiconductor optical amplifier

Taking into account ultra-fast carrier dynamics, this paper models 640 Gbit/s wavelength conversion scheme based on nonlinear polarization rotation （NPR） in a single semiconductor optical amplifier （SOA） and investigates the performance of this kind of wavelength conversion scheme in detail. In this model, two carrier temperature equations are introduced to substitute two energy density equations, which reduce the complexity of calculation in comparison with the previous model. The temporary gain and phase shift dynamics induced by ultra-short optical pulses are numerically simulated and the simulated results are qualitatively in good agreement with reported experimental results. Simulated results show that non-inverted and inverted 640 Gbit/s wavelength conversions based on NPR are achieved with clear open eye diagrams. To further investigate the performance of the non-inverted wavelength conversion scheme, the dependence of output extinction ratio （ER） on some key parameters used in simulation is illustrated. Furthermore, simulated analyses show that high performance non-inverted wavelength conversion based on NPR can be achieved by using a red-shifted filtering scheme.

Performance analysis of optical burst switching node with limited wavelength conversion capabilities

The systematical and scalable frameworks were provided for estimating the blocking probabilities under asynchronous traffic in optical burst switching(OBS) nodes with limited wavelength conversion capability(LWCC) . The relevant system architectures of limited range and limited number of wavelength converters(WCs) deployed by a share-per-fiber(SPF) mode were developed,and the novel theoretical analysis of node blocking probability was derived by combining the calculation of discouraged arrival rate in a birth-death process and two-dimensional Markov chain model of SPF. The simulation results on single node performance verify the accuracy and effectiveness of the analysis models. Under most scenarios,it is difficult to distinguish the plots generated by the analysis and simulation. As the conversion degree increases,the accuracy of the analysis model worsens slightly. However,the utmost error on burst loss probability is far less than one order of magnitude and hence,still allows for an accurate estimate. Some results are of actual significance to the construction of next-generation commercial OBS backbones.

All optical wavelength converter and its application in optical network

All optical network （AON） is a hot topic in recent studies of optical fiber communications. Key techniques in AON include optical switching/routing, optical cross connection （OXC）, all optical wavelength conversion （AOWC）, all optical buffering, etc. Opti- cal switching/routing is in fact wavelength switching/ routing. OXC and wavelength conversion （WC） are introduced into cross nodes so that a virtual wavelength path is established. With WC, communication route is formed only if there is unused wavelength in an individual segment link. The rate wavelength usage is thus greatly increased. The blocking rate of network can be reduced by adding WCs, especially for huge capacity multiple nodes ones. Therefore, WC has attracted much attention in basic research of optical communication and is used in some experimental networks.This dissertation studies all optic wavelength conversion and its application, with the contributions in the following five aspects.

Hybrid WDM/TDM PON system employing an all-optical wavelength converter

A new hybrid WDM/TDM passive optical network （PON） implemented by using all-optical wavelength converters （AOWCs） is proposed. The AOWCs are based on the cross-gain modulation （XGM） effect of the semiconductor optical amplifier （SOA）. Moreover, the feasibility of this sys- tem is experimentally demonstrated by evaluating the impacts of the optical wavelength conversion, time domain waveforms, eye diagrams and bit-error-rate （BER） in AOWC. The results show that the proposal will be a promising solution for the next generation access networks.

Cascaded four-wave mixing all-optical wavelength converter based on highly nonlinear fiber deposited graphene oxide

The all-optical wavelength conversion using cascaded four-wave mixing(FWM)phenomena with graphene oxide(GO)and a highly nonlinear fiber(HNLF)device is demonstrated experimentally.GO has a strong third-order nonlinear effect and is an excellent nonlinear optical material for nonlinear optical wavelength conversion.The group velocity matching of pump and signal,HNLF,and GO amplification promote the cascaded nonlinear frequency mixing process.From the experimental and analytical results,the maximum spacing between signal and pump is 21 nm,and specifically,the order of cascaded FWM light increases from order 1 to order 2 with increasing GO,and the first-order FWM conversion effi-ciency increases to a maximum of−14.5 dB.To the best of our knowledge,this is the first time that cascaded FWM-based all-optical wavelength conversion in HNLF-GO with wide wavelength selectivity is investigated with combined pump and signal light.Our findings not only provide an effective method for achieving all-optical wavelength conversion in cascaded FWM but also offer the possibility of fabricating high-performance nonlinear optical devices.

Analytic approach to the small-signal frequency response of saturated semiconductor optical amplifiers using multisection model

An analytic solution derived by multisection model to the small-signal frequency response （SSFR） of wavelength conversion based on cross-gain modulation （XGM） in semiconductor optical amplifiers （SOAs） is presented. The result contains details that can affect the characteristics of SSFR significantly more than previous ones.

基于EDFA+NDF的AOWC转换效率的仿真研究

介绍了基于EDFA+NDF实现波长转换的理论模型,借助OptiSystem软件重点研究了影响波长转换效率的几个特性参数,即EDFA的泵浦增益值的大小、光纤的衰减系数、非线性色散光纤的长度和光纤的有效面积,最后给出一组合理的参数使波长转换器有15.149dB的转换效率,这对于优化基于ED-FA+NDF的全光波长转换器有重要参考价值。

基于DFG-AOWC的泵浦带宽与调谐研究

提出了差频产生型全光波长转换器的重要技术问题泵浦带宽的改善方法.介绍了差频产生型 全光波长转换器的基本原理,分析了产生有限的泵浦与信号光带宽的原因,提出与论证了在QPM光栅波导 中引入按一定规律分布的π相移域来增加泵浦波长可变范围的方法.结果表明对于解决DFG AOWC的泵浦 带宽问题具有较大的意义.

FSK Modulation Scheme for High-Speed Optical Transmission

In this paper, we describe the generation, detection, and performance of frequency-shift keying （FSK） for high-speed optical transmission and label switching. A non-return-to-zero （NRZ） FSK signal is generated by using two continuous-wave （CW） lasers, one Mach-Zehnder modulator （MZM）, and one Mach-Zehnder delay interferometer （MZDI）. An RZ-FSK signal is generated by cascading a dual-arm MZM, which is driven by a sinusoidal voltage at half the bit rate. Demodulation can be achieved on 1 bit rate through one MZDI or an array waveguide grating （AWG） demultiplexer with balanced detection. We perform numerical simulation on two types of frequency modulation schemes using MZM or PM, and we determine the effect of frequency tone spacing （FTS） on the generated FSK signal. In the proposed scheme, a novel frequency modulation format has transmission advantages compared with traditional modulation formats such as RZ and differential phase-shift keying （DPSK）, under varying dispersion management. The performance of an RZ-FSK signal in a 4 x 40 Gb/s WDM transmission system is discussed. We experiment on transparent wavelength conversion based on four-wave mixing （FWM） in a semiconductor optical amplifier （SOA） and in a highly nonlinear dispersion shifted fiber （HNDSF） for a 40 Gb/s RZ-FSK signal. The feasibility of all-optical signal processing of a high-speed RZ-FSK signal is confirmed. We also determine the receiver power penalty for the RZ-FSK signal after a 100 km standard single-mode fiber （SMF） transmission link with matching dispersion compensating fiber （DCF）, under the post-compensation management scheme. Because the frequency modulation format is orthogonal to intensity modulation and vector modulation （polarization shift keying）, it can be used in the context of the combined modulation format to decrease the data rate or enhance the symbol rate. It can also be used in orthogonal label-switching as the modulation format for the payload or the label. As an example, we propose a simple orthogonal optical label switching technique based on 40 Gb/s FSK payload and 2.5 Gb/s intensity modulated （IM） label.

All-optical NRZ wavelength conversion using a Sagnac loop with optimized SOA characteristics

We investigated the all-optical wavelength conversion technique for non-return-to-zero（NRZ） signals based on a Sagnac loop interferometer using an SOA. For the wavelength conversion of the NRZ signal at and above40 Gbit/s, we used an in-house numerical SOA model to analyze the influence of the SOA carrier characteristics and the SOA length on the performance of the Sagnac loop. We found that the SOA carrier recovery time should be between 2 and 3 times of one bit duration in order to get optimum NRZ wavelength conversion. In addition to the carrier recovery time requirement, SOAs with a shorter physical length are preferred to be used in the Sagnac interferometer.

采用SOA-Sagnac光纤干涉仪的AOWC研究与实验

对采用SOA-Sagnac光纤干涉仪的全光波长变换器(AOWC)从理论上进行了较为详细的研究,首次根据光路合成法求出SOA-Sagnac光纤干涉仪的响应函数,并构成了一套实验系统,测量了SOA的增益、带宽与输入光功率的关系,测量了输出信号的消光比以及输入、输出信号的波形和眼图,并对它们进行了比较。

A periodically poled LiNbO_3 optical parametric generator in wavelength conversion from 2 to 3.88——4.34 μm

A periodically poled lithium niobate （PPLN） optical parametric generator （OPG） pumped by a laser diode （LD）-pumped Q-switched Tm,Ho：GdVO4 laser operated at 2.048 μm with pump pulse of 25 ns and repetition rate of 10 kHz is reported. A continuous tunable middle-infrared （mid-IR） spectrum of 3.88 - 4.34 μm is obtained by changing the crystal temperature from 50 to 124℃. When the incident pump power is 3 W, the total OPG output power is 95 mW, corresponding to optical conversion efficiency of 3.2%.

All-optical wavelength converter using a microdisk resonator integrated with p-n junctions

We explore all-optical wavelength conversion in a microdisk resonator integrated with interleaved p-n junctions.Numerical simulation based on temporal coupled mode theory is performed to study the free-carrier dynamics inside the cavity.It reveals that the detuning of pump and probe frequencies and the carrier lifetime have a significant effect on the device performance.Experimental result confirms that the conversion speed can be considerably improved by applying a reverse bias on the p-n junctions.Wavelength conversion at 10 Gb/s data rate is achieved with a pump power of 5.41 dBm and a bias voltage of-6 V.

高功率无线光通信波长转换系统性能研究

针对水下高速无线激光通信发射功率较低,通信距离受限的问题,该研究采用非线性光学中二次谐波理论,将1064 nm的高速外调制与放大技术和非线性晶体的准相位匹配技术相结合,通过光学设计和系统参数研究,设计了一种532 nm的高速大功率无线激光调制发射系统,并建立了基于温度和角度变换的波长转换效率模型。然后通过仿真分析的方法得到了不同温度下,最大转换效率对应的角度范围。最后对系统的性能进行了系统搭建和实验分析,验证了该系统在常温下可实现1 W大功率532 nm绿光无线输出,且频率大于1 GHz的模拟信号和速率大于500 Mbps的数字信号调制。实验结果表明:常温下,该系统输出的光斑光强分布均匀,光束质量显著好于调制后的基频光模式。系统输出的方波信号上升沿宽度和下降沿宽度会发生压缩,但随着脉冲宽度的减小压缩现象会发生收敛,上升沿宽度收敛于0.27,下降沿宽度收敛于0.06,系统输出的正弦信号随着频率的增加没有发生明显的畸变。研究结果可以为未来水下长距离高速无线光通信应用提供理论和技术支撑。

Optical Wavelength Filter Using Mode Conversion in Multimode Waveguide

A wavelength filter with simple structure using multimode waveguide is proposed. The device uses mode conversion by a grating structure fabricated simultaneously with the multimode waveguide.

40 Gb/s NRZ-DQPSK data wavelength conversion with amplitude regeneration using four-wave mixing in a quantum dash semiconductor optical amplifier

Differential quadrature phase shift keying （DQPSK） modulation is attractive in high-speed optical communications because of its resistance to fiber non-linearities and more efficient use of fiber bandwidth compared to conventional intensity modulation schemes. Because of its wavelength conversion ability and phase preservation, semiconductor optical amplifier （SOA） four- wave mixing （FWM） has attracted much attention. We experimentally study wavelength conversion of 40 Gbit/s （20 Gbaud） non-return-to-zero （NRZ）-DQPSK data using FWM in a quantum dash SOA with 20 dB gain and 5 dBm output saturation power. Q factor improvement and eye diagram reshaping is shown for up to 3 nm pump-probe detuning and is superior to that reported for a higher gain bulk SOA.

Novel configuration for wavelength conversion based on cross-gain modulation in semiconductor optical amplifiers

Novel configuration for cross-gain modulation (XGM) wavelength conversion based on the single-port-coupled semiconductor optical amplifier (SOA), in which the input and the output share one port, has been demonstrated with the output extinction ratio as high as 15 dB, even in the 2.5 Gbit/s wavelength up conversion with a 12.8 nm span. Owing to the existence of double-pass gain and the transmission loss of the rear facet, the novel scheme can be achieved with simpler implementation and higher output extinction ratio, compared with the conventional schemes based on double-port-coupled SOA either with identical long chip or double long chip.

DWDM光传送网中选路和波长分配

本文综述了密集波分复用 (DWDM)光传送网中选路和波长分配 (RAW )研究领域的最新研究成果。分析比较了固定路由和备用路由下不同RAW算法的性能 。

基于光纤中受激喇曼散射效应的全光多波长转换耦合器

基于光纤中受激喇曼散射效应,运用级联同种光纤设计出全光多波长转换耦合器,使转换输出的各路信号光功率相等.建立了全光多波长转换设计方案的理论模型,给出了设计原理框图以及实现方法,并以1路泵浦信号光、4路连续探测光为例,通过OptiSystem软件进行了仿真,仿真结果表明:所设计的全光多波长转换耦合器能同时对4路探测光实现波长转换,转换输出的信号光码型和输入泵浦信号光码型基本一致;转换效率和消光比随着探测光波长的增大而增大,最大值分别为-34dB和36.68dB;Q因子随着探测光波长的增大而减少,最大值为128.29;在级联光纤之后,4路输出信号光峰值功率和消光比基本相等,Q因子整体数值相对于全光多波长转换后有所下降,最大值为89.5455,验证了该方案的可行性.