All-optical wavelength converters for phase modulated data signals in system experiments

这一后续项目是清华大学（清华大学，中国北京）的两个中国小组和三个德国小组（柏林技术大学（TUB）、帕德博恩大学（UOP）、弗劳恩霍夫电信研究所-海因里希-赫兹研究所（HHI））联合研究方案的一部分。与项目前两年一样，科学合作的框架是利用波长转换解决光突发交换（OBS）网络中的竞争问题，该子项目的目标是在前一个项目阶段的基础上继续全光波长转换器（AOWC）的实验研究。所研究的波长转换器将利用功能光纤中的非线性光学效应，如高度非线性光纤（HNLF），周期性极化铌酸锂（PPLN）和半导体光放大器（SOA）。所研究的设备部分由其他合作伙伴的子项目实现，例如UOP（基于PPLN的设备）和清华大学（基于SOA的设备），部分由该子项目中的HHI实现（基于HNLF的设备）。重点是AOWC，它对调制格式是透明的，即可以用相位调制和幅度调制的光数据信号来操作。在上一个项目期间，长距离传输中的物理层发展已经证实了高级相位调制格式（例如差分相移键控（DPSK）和差分正交相移键控（DQPSK）[1]）的重要性迅速增长。因此，后续项目将继续集中在高阶相位调制数据信号的转换。在上一个项目期间的结果的基础上，在未来两年期间的工作将集中在三个主要课题。第一个是四波混频和光参量放大在HNLF使用先进的泵浦方案和改进的功能光纤。第二是在PPLN中使用一种新的方案（差频和频产生）进行波长转换以及PPLN中光参量放大的基本考虑。由于中国项目合作伙伴取得了令人鼓舞的成果，第三个主题将是SOA中的四波混频。基于SOA的AOWC概念的研究将与中国合作伙伴密切合作。开发的AOWC概念的特点和比较使用的评价标准，在前一个项目期间和系统实验的符号速率为10，40，80和160 Gbaud。最近，对使用50和100 Gbaud的符号率结合高阶调制格式的100 Gbit/s传输系统的研究已经加强。其主要原因是人们对100 Gbit以太网作为本地、地铁和长途传输中的新技术越来越感兴趣，这也是来自IEEE或ITU-T等标准化机构的兴趣。因此，根据所需子组件的可用性，将考虑在系统实验中使用50或100 Gbaud。为了与中国合作伙伴合作对基于SOA的AOWC进行研究，最初计划的关于HHI AOWC动态响应和瞬态行为的工作将减少到理论研究，主要由UOP和TUB完成。

This follow-up project is part of a joint research programme of two Chinese groups at the Tsinghua-University (THU, Beijing, China) and of three German groups (Technical University Berlin (TUB), University of Paderborn (UOP), Fraunhofer-lnstitute for Telecommunications - Heinrich-Hertz-Institut (HHI)). The frame of scientific cooperation is, as in the first two years of the project, the topic of contention resolution in optical burst switching (OBS) networks by wavelength conversion.The objective of this sub-project is to continue the experimental investigation on all-optical wavelength converters (AOWCs) based on the results of the previous project period. The investigated wavelength converters will use nonlinear optical effects in functional fibers like highly nonlinear fibers (HNLF), in periodically poled Lithium Niobate (PPLN) and in semiconductor optical amplifiers (SOA). The investigated devices are partly realized by the sub-projects of the other partners, e.g. the UOP (PPLN-based devices) and Tsinghua- University (SOA-based devices) and partly by the HHI within this sub-project {HNLFbased devices). The focus is on AOWCs, which are transparent to the modulation format, i.e. which can be operated with phase-modulated and amplitude modulated optical data signals. The physical layer developments in long-distance transport in the previous project period have confirmed the rapid growing importance of advanced phase modulation formats (such as differential-phase-shift keying (DPSK) and differential quadrature phase shift keying (DQPSK) [1]). Therefore the follow-up project will continue to focus on conversion of higher order phase modulated data signals.Based on the results of the previous project period, the work in next two year period will concentrate on three main topics. The first is four-wave mixing and optical parametric amplification in HNLF using advanced pumping schemes and improved functional fibers. The second is the use of a new scheme (difference and sum frequency generation) in PPLN for wavelength conversion and the basic consideration of optical parametric amplification in PPLN. Due to promising results obtained by the Chinese project partners, the third topic will be four-wave mixing in SOAs. The investigations on AOWC concepts based on SOAs will be done in close collaboration with the Chinese partners. The developed AOWC concepts will be characterized and compared using the evaluation criteria derived in the previous project period and by system experiments with symbol rates of 10, 40, 80 and 160Gbaud. Recently research on transmission systems with 100Gbit/s using symbol rates of 50 and lOOGbaud in combination with higher order modulation formats has intensified. The main reason is a growing interest, also from standardization bodies like IEEE or ITU-T, in lOOGbit Ethernet as a new technology in local, metro and long-haul transport. Therefore the use of 50 or 100 Gbaud in the system experiments will be considered, depending on the availability of the required subcomponents.To allow investigations on SOA-based AOWCs in cooperation with the Chinese partners, the initially planned work on dynamic response and transient behaviour of AOWCs at the HHI will be reduced to theoretical investigations, mainly done by the UOP and the TUB.