Bandwidth virtualization enables long-haul WDM transport of 40 Gb/s and 100 Gb/s services

This article describes how bandwidth virtualization can enable transmission of ultra-high bandwidth 40 Gb/s and 100 Gb/s services over existing optical transport networks independently of the underlying network infrastructure. An overview of the technology alternatives available to enable high-bandwidth service transport is provided, along with a discussion of the relative merits of different approaches. The authors describe how wavelength division multiplexing, using large- scale photonic integrated circuits combined with the use of a digital virtual concatenation mapping protocol, can be used to enable decoupling of 40 Gb/s and 100 Gb/s service provisioning from the underlying optical link engineering, thereby enabling bandwidth virtualization. Real-world implementation examples of bandwidth virtualization are provided, including 40 Gb/s service transmission over a 2000-km fiber link with 65 ps of peak PMD, a field trial of 40 Gb/s service transmission over an 8477-km trans-oceanic network, and finally a field trial of a pre-standard 100 gigabit Ethernet service transmission over a 4000-km terrestrial long-haul network.     

Wavelength shift keying modulation up to 35 Gb/s with wavelength tone reuse to multiplex two 40 Gb/s DPSK signals

Fast optical frequency shift keying or wavelength shift keying (WSK) modulation offers advantageous features for applications in long haul communications and in optical labeling for packet routing. This includes simple demodulation by optical filtering and constant amplitude envelope providing tolerance to fiber nonlinear effects during transmission. In this paper we report on the generation of WSK signals up to 35 Gb/s with reuse of the wavelength tones for polarization multiplexing two independent 40 Gb/s DPSK signals. Transmission over a 50 km fiber link of the resultant three channel signal is also reported.     

利用光时分复用技术实现5Gb／s的孤子传输

利用光纤环激光器作为孤子源和光时分复用技术成功地进行了５Ｇｂ／ｓ的孤子传输实验。研究了在相同的入纤工上，光脉冲的波工对孤子的传输性能的影响，在实验的波长范围内的测量表明，波长越长出纤脉冲的时域宽度越窄，但脉冲的频谱的变化基本与波无关，对实验结果进行了数值模拟分析，实验结果基本与数值模拟的一致。     

An Overlay Photonic Layer Security Approach Scalable to 100 Gb/s [Topics in Optical Communications]

As data rates outpace the capabilities of electronic encryption schemes, photonic layer security may fill the gap in providing a communication security solution at high data rates. In this article we review and highlight the advantages of our proposed optical code-division multiplexed (OCDM)-based photonic layer security (PLS) system based on high-resolution control of the optical phase of tightly spaced phase locked laser lines. Such a PLS system is scaleable to 100 Gb/s and provides a protocol independent security solution. We review the use of high-resolution control of the optical phase of mode-locked laser frequency combs as an enabling technology for a new class of OCDM systems. A network based on such systems is compatible with and can have comparable spectral efficiency to existing DWDM networks. Through inverse multiplexing of 10 Gb/s tributaries, we have already demonstrated optical transmission of a 40 Gb/s aggregate OCDM signal over 400 km. Such a PLS solution is achieved through shared phase scrambling of the individual OCDM codes assigned to each of the tributaries using an integrated micro-ring resonator-based phase coder/ scrambler. The confidentiality of OCDM-based PLS is robust against exhaustive, known plain text, and archival/forensic attacks, and can complement digital encryption operating at higher layers. Moreover, the integrity of the PLS solution is ensured through the inherent coupling to confidentiality, since knowledge of the key is needed in order to easily alter the transmitted data stream without introducing observable errors. This system can leverage advances in optical integration to support new applications where electronic encryption is impractical because of space, weight, power, availability, and cost requirements. Such applications range from timely security support for the emerging 100 GbE standards to all-optical multilevel security offered through the compatibility of PLS with transparent DWDM networks.     

Greater than 200 Gb/s Transmission Using Direct-Detection Optical OFDM Superchannel

In this paper, we propose direct-detection optical orthogonal frequency division multiplexing superchannel (DDO-OFDM-S) and optical multiband receiving method (OMBR) to support a greater than 200 Gb/s data rate and longer distance for direct-detection systems. For the new OMBR, we discuss the optimum carrier-to-sideband power ratio (CSPR) in the cases of back-to-back and post transmission. We derive the analytical form for CSPR and theoretically verify it. A low overhead training method for estimating I/Q imbalance is also introduced in order to improve performance and maintain high system throughput. The experiment results show that these proposals enable an unprecedented data rate of 214 Gb/s (190 Gb/s without overhead) per wavelength over an unprecedented distance of 720 km SSMF in greater than 100 Gb/s DDO-OFDM systems.     

T比特频分复用相干光传输技术

高清电视、视频点播、云计算等新业务的发展要求光纤传送网带宽大并能灵活调度。文章讨论了几种实现传输速率为T比特每秒的超级信道产生方法。受电子＂瓶颈＂限制,T比特级速率的传输必须由多个密集的正交光子载波组成的超级信道承载。在每个光子载波上,可以采用基于正交频分复用的多载波技术,也可以采用单载波时域或频域均衡技术。通过调整光子载波的数目与颗粒度,或每个光子载波上承载的调制格式,可以实现可变速率的光传输与光交换。     

160 Gb/s Time-Domain Channel Extraction/Insertion and All-Optical Logic Operations Exploiting a Single PPLN Waveguide

160 Gb/s all-optical signal processing is demonstrated exploiting pump depletion in addition to sum and difference frequency generation (SFG/DFG) in a single periodically poled lithium-niobate (PPLN) waveguide. 160 Gb/s time-domain extraction and insertion operations of channels are obtained in an optical time division multiplexing (OTDM) system. Moreover, 160 Gb/s digital operations including half-adder, half-subtracter and and/or/xor functions are carried out. The use of pump depletion effect allows to process ultrafast signals due to its high efficiency and ultrafast dynamics. 160 Gb/s bit error rate (BER) measurements confirm the effectiveness of all presented functionalities.      

P比特光交换节点研究

光网络中引入全光交换技术可以无需进行光电光转换和电信号处理,使网络具备透明性,大大降低节点的复杂性和节点成本。多粒度交换节点减小了交换矩阵的规模,降低了交换矩阵的复杂性,是波分复用（WDM）网络节点发展的一个方向。随着正交频分复用（OFDM）技术的引入,带宽可变的节点技术得到了越来越广泛的关注。文章介绍了传统的基于波长的光交叉连接器（OXC）交换结构、多粒度交换结构,以及基于正交频分复用/单载波频分复用（OFDM/SCFDM）的节点交换结构,并通过实验对基于带宽可变的可重构的光分插复用器（ROADM）、OXC节点技术进行了验证。在实验中提出的基于子波带的交换结构中,节点容量达到了P比特量级。     

A 10 Gb/s optical code division multiplexing using 8-chip opticalbipolar code and coherent detection

bOptical code division multiplexing (OCDM) using optical bipolar code and coherent detection is a new multiplexing method for future fiber-optic communication networks. Some optical bipolar codes, which are described by the combination of phase of optical chip pulses, with a repetition frequency 10 GHz are generated experimentally. Temporal matched filtering for the 10 Gb/s OCDM is demonstrated using optical encoder and decoder, and their fundamental properties are investigated. Effect of interference code is shown experimentally and discussed. The novel coherent detection system with autocorrelation sidelobe suppression using balanced detector and local light source is proposed. The pseudocoherent detection is demonstrated experimentally by using a clock pulse. Advantageous properties of the coherent detection are shown. The fundamental functions to realize the gigabit rate OCDM system is revealed     

PetaStar: a petabit photonic packet switch

This paper presents a new petabit photonic packet switch architecture, called PetaStar. Using a new multidimensional photonic multiplexing scheme that includes space, time, wavelength, and subcarrier domains, PetaStar is based on a three-stage Clos-network photonic switch fabric to provide scalable large-dimension switch interconnections with nanosecond reconfiguration speed. Packet buffering is implemented electronically at the input and output port controllers, allowing the central photonic switch fabric to transport high-speed optical signals without electrical-to-optical conversion. Optical time-division multiplexing technology further scales port speed beyond electronic speed up to 160 Gb/s to minimize the fiber connections. To solve output port contention and internal blocking in the three-stage Clos-network switch, we present a new matching scheme, called c-MAC, a concurrent matching algorithm for Clos-network switches. It is highly distributed such that the input-output matching and routing-path finding are concurrently performed by scheduling modules. One feasible architecture for the c-MAC scheme, where a crosspoint switch is used to provide the interconnections between the arbitration modules, is also proposed. With the c-MAC scheme, and an internal speedup of 1.5, PetaStar with a switch size of 6400 /spl times/ 6400 and total capacity of 1.024 petabit/s can be achieved at a throughput close to 100% under various traffic conditions.     

2.5Gb/s FSO-OFDM系统调制方式研究

OFDM是一种能有效抵御大气散射效应的调制技术,提出了一种实现FSO-OFDM传输的系统方案。对速率为2.5Gb/s的FSO-OFDM系统在不同的天气条件下进行了仿真研究。仿真分析了不同的调制方式和不同的子载波数时FSO-OFDM系统的误码率和光信噪比。仿真结果表明,与采用16PSK调制方式相比,采用16QAM方式系统将具有更低的误码率和更高的Q值。     

Terahipas: a modular and expandable terabit/second hierarchicallymultiplexing photonic ATM switch architecture

A terabit/second hierarchically multiplexing photonic asynchronous transfer mode (ATM) switch network architecture, called Terahipas, is proposed. It combines the advantages of photonics (a large bandwidth for transport of cells) and electronics (advanced logical functions for controlling, processing, and routing). It uses a hierarchical photonic multiplexing structure in which several tens of channels with a relatively low bit rate, say 2.4 Gb/s, are first time-multiplexed on an optical highway by shrinking the interval between optical pulses, then a number of optical highways are wavelength-multiplexed (or space-division multiplexed). As a result, the switch capacity can be expanded from the order of 100 Gb/s to the order of 10 Tb/s in a modular fashion. A new implementation scheme for cell buffering is used for eliminating the bottleneck when receiving and storing concurrent optical cells at bit rates as high as 100 Gb/s. This new architecture can serve as the basis of a modular, expandable, high-performance ATM switching system for future broad band integrated service digital networks (B-ISDN's)     

All-optical TDM data demultiplexing at 80 Gb/s with significant timing jitter tolerance using a fiber Bragg grating based rectangular pulse switching technology

We demonstrate the use of fiber Bragg grating based pulse-shaping technology to provide timing jitter tolerant data demultiplexing in an 80 Gb/s all-optical time division multiplexing (OTDM) system. Error-free demultiplexing operation is achieved with /spl sim/6 ps timing jitter tolerance using superstructured fiber Bragg grating based 1.7 ps soliton to 10 ps rectangular pulse conversion at the switching pulse input to a nonlinear optical loop mirror (NOLM) demultiplexer comprising highly nonlinear dispersion shifted fiber (HNLF). A 2-dB power-penalty improvement is obtained compared to demultiplexing without the pulse-shaping grating.     

Experimental Demonstration and Numerical Simulation of 107-Gb/s High Spectral Efficiency Coherent Optical OFDM

Orthogonal frequency-division multiplexing (OFDM) is a multicarrier modulation format in which the data are transmitted with a set of orthogonal subcarriers. Recently, this modulation format has been actively explored in the field of optical communications to take advantages of its high spectral efficiency and resilience to chromatic and polarization dispersion. However, to realize the optical OFDM at 100 Gb/s and beyond requires extremely high electronic bandwidth for the electronic signal processing elements. In this paper, we investigate orthogonal-band-multiplexed OFDM (OBM-OFDM) as a suitable modulation and multiplexing scheme for achieving bandwidth scalable and spectral efficient long-haul transmission systems. The OBM-OFDM signal can be implemented in either RF domain, or optical domain, or a combination of both domains. Using the scheme of OBM-OFDM, we show the successful transmission of 107 Gb/s data rate over 1000-km standard single-mode fiber (SSMF) without optical dispersion compensation and without Raman amplification. The demonstrated OBM-OFDM system is realized in optical domain which employs 2 $times$ 2 MIMO-OFDM signal processing and achieves high optical spectral efficiency of 3.3 bit/s/Hz using 4-QAM encoding. Additionally, we perform numerical simulation of 107-Gb/s CO-OFDM transmission for both single-channel and wavelength-division-multiplexed (WDM) systems. We find that the $Q$ -factor of OBM-OFDM measured using uniform filling of OFDM subbands is in fact more conservative, in particular, is 1.2 dB and 0.4 dB lower than using random filling for single-channel and WDM systems, respectively.      

基于频域均衡的Tb/s级相干光单载波系统

对相干光单载波频域均衡系统(CO-SCFDE)、相干光单载波频分复用系统(CO-SCFDM)以及相干光正交频分复用系统(CO-OFDM)的理论和实验进行了对比研究,结果表明基于频域均衡的相干光单载波系统既保留了正交频分复用方式计算复杂度较低、频谱效率高和抗色散性能好的优点,又有效地减小了光纤非线性带来的传输损伤,是高速长距离光纤传输的一种有潜力的技术方案。     

110 channels×2.35 Gb/s from a single femtosecond laser

We demonstrate the feasibility of a wavelength-division-multiplexed transmitter using a single femtosecond laser and generating 110 channels at 2.35 Gb/s. Chirped-pulse wavelength-division multiplexing is used to carve channels spaced by about 0.3 nm out of the broad spectrum of the laser. A 64-fold increase in bit rate per channel is accomplished through optical time-division multiplexing     

2.488 Gb/s SONET multiplexer/demultiplexer with frame detectioncapability

The authors describe a novel scheme that allows a demultiplexer, a byte aligner, and a frame detection circuit tube to be integrated on one chip without compromising the demultiplexer's performance. A research prototype integrated circuit (IC) that incorporates this scheme was designed to operate at speeds up to the SONET STS-48 (synchronous transport signal level 48) rate of 2.488 Gb/s. The IC is implemented in GaAs enhancement/depletion mode MESFET technology, and it performs 1:8 demultiplexing, byte alignment, and SONET frame detection functions. A separate IC that performs 8:1 multiplexing was also implemented using the same technology. The bit error rate; test results show that the multiplexer and demultiplexer with frame detector can operate at 2.488 Gb/s with a bit error rate less than 1×10^-14. Both ICs were tested at data rates up to 3 Gb/s     

OTDM-based optical communications networks at 160 Gbit/s and beyond

The virtually unlimited bandwidth of optical fibers has caused a great increase in data transmission speed over the past decade and, hence, stimulated high-demand multimedia services. Nowadays, opto-electronic conversion is still required at each network node to process the incoming signal. However, when the single channel bit rate increases beyond electronic speed limit, optical time division multiplexing (OTDM) becomes a forced choice, and all-optical processing must be performed to extract the information from the incoming packet. In this paper the state of art, the advantages and drawbacks of the OTDM technology will be discussed in order to highlight its potentialities in different application scenarios for optical communications networks, and its perspectives in different temporal horizons. In detail, a recent experiment of a 160 Gbit/s OTDM system is presented. Furthermore, a photonic node architecture suitable for optical packet switching networks is proposed, and possible solutions for the implementation of all the required subsystems are presented and compared in order to optimize the node performance. In particular innovative schemes for optical add/drop multiplexer, optical logic gates, optical switches, and optical flip-flop are introduced with a particular emphasis on emerging nonlinear materials and enabling technologies.     

2.5 Gb/s偏振模色散自动补偿对偏振模色散容限值的影响

在我国现有的光纤通信骨干网中,绝大部分速率为2.5 Gb/s。今后如在我国现有的2.5 Gb/s网络系统上进行密集波分复用(DWDM)升级,亦需要考虑偏振模色散(PMD)对系统容量升级的影响。采用十段高双折射光纤级联而成的偏振模色散模拟器模拟实际光纤,从信号中提取基带频率分量作为反馈信号,对2.5 Gb/s系统进行了偏振模色散自动补偿实验,并对反馈前后的系统进行了系统代价的测量和比较。实验结果表明,偏振模色散自动补偿能较大幅度地提高系统的偏振模色散容限值。     

OTDM add-drop multiplexer based on time-frequency signal processing

A time-division add-drop multiplexer capable of high-extinction-ratio operation is presented both theoretically and experimentally. The approach used is based on time-to-frequency domain conversion of optical signals and relies upon the switching of linearly chirped optical pulses. By converting a 40-Gb/s optical time-division multiplexing (OTDM) signal to 4 /spl times/ 10-Gb/s wavelength-division multiplexing (WDM) channels and using fiber Bragg gratings for frequency-domain add-drop multiplexing, a timeslot suppression ratio in excess of 30 dB and error-free operation for the dropped, through, and added channels were achieved. A further stage of WDM-to-TDM signal conversion was used to map the resulting signal back into the time domain. Moreover, it is shown that it is straightforward to simultaneously operate on multiple channels by simply cascading gratings to make more complex filtering functions without the requirement for any further synchronization of the tributary channels.