Field trial of data-granularity-flexible reconfigurable OADM with wavelength-packet-selective switch

Reconfigurable optical add/drop multiplexers (ROADMs), which enable dynamic and flexible node-to-node connection via wavelength paths, are key components in metro ring network nodes. A data-granularity-flexible ROADM node that combines a wavelength-tunable filter, and an optical packet ADM (PADM) has been proposed and demonstrated. In this paper, the first field trial of the data-granularity-flexible ROADM network with wavelength- and packet-selective switch is demonstrated using a novel concurrent generation technique of address-reconfigurable optical-code (OC) labels and payload data. Bit error rates (BERs) of less than 10/sup -12/ for all 16-wavelength channels are obtained over 90 km of transmission at 10 Gb/s.     

Mathematical formulation of provisioning of connections with advance reservation in metro WDM ring networks using reconfigurable OADMs (ROADMs) with tuning constraint

Optical add/drop multiplexers (OADMs) can significantly reduce the cost of metro optical wavelength-division multiplexing (WDM) ring networks by allowing traffic to bypass intermediate nodes without expensive opto-electro-opto (O-E-O) conversion. Some traditional OADMs, called fixed OADMs (FOADMs), can only add/drop traffic on a specific wavelength. Reconfigurable Optical Add/Drop Multiplexers (ROADMs) are emerging, which can add/drop traffic onto/from different wavelengths at different time. ROADMs provide desirable flexibility, enable fast provisioning of dynamic traffic, and save capital expenditure (CapEx) and operational expenditure (OpEx). In order to be cost-effective, some ROADMs employ architectures that tune the ROADM continuously from one wavelength to another, crossing through all the wavelengths in-between, which may cause interference to the connections, if any, on those wavelengths being crossed. In order to prevent existing connections from being interrupted, a constraint needs to be imposed that ROADMs cannot cross working wavelengths when tuning. In this study, the design and the benefits of metro optical WDM network architectures using ROADMs and the impact of this tuning constraint on the performance of the network are investigated. Mathematical formulation of the problem of provisioning of connections with advance reservation, in which the arrival time and departure time of all the connections are known in advance, is presented, and results for a small network are shown.     

Online connection provisioning in metro optical WDM networks using reconfigurable OADMs

Optical add/drop multiplexers (OADMs) can significantly reduce the cost of metro optical wavelength-division multiplexing (WDM) ring networks by allowing traffic to bypass intermediate nodes without expensive opto-electro-opto (O-E-O) conversion. Some traditional OADMs, called fixed OADMs (FOADMs), can only add/drop traffic on a specific wavelength. Reconfigurable OADMs (ROADMs) are emerging, which can add/drop traffic onto/from different wavelengths at different time. ROADMs provide desirable flexibility, enable fast provisioning of dynamic traffic, and save capital expenditure (CapEx) and operational expenditure (OpEx). In order to be cost effective, some ROADMs employ architectures that tune the ROADM continuously from one wavelength to another, crossing through all the wavelengths in between, which may cause interference to the connections, if any, on those wavelengths being crossed. In order to prevent existing connections from being interrupted, a constraint needs to be imposed that ROADMs cannot cross working wavelengths when tuning. In this paper, the design and the benefits of metro optical WDM network architectures using ROADMs and the impact of this tuning constraint on the performance of the network are investigated. The dynamic traffic provisioning problem is analyzed and divided into two subproblems: 1) a traditional one on resource allocation; and 2) a new subproblem on tuning-head positioning (TP). Several heuristics for each subproblem are developed to combat the tuning constraint. Results from our simulation experiments show that the tuning constraint can significantly affect the network performance in terms of overall connection blocking probability, and good heuristics for network control and management are needed to overcome this tuning constraint.     

40-Gb/s packet-selective photonic add/drop multiplexer based on optical-code label header processing

A packet-by-packet-selective photonic add/drop multiplexer, of the finest data granularity, is experimentally demonstrated at 40 Gb/s. An optical-code label, attached to the packet, enables determination, in the optical domain, of whether to drop, cut through, or add packets.     

Routing,wavelength assignment and spectrum allocation for reconfigurable optical mesh networks having a combination of fixed and flexible spectrum ROADM nodes

Next generation of optical networks will witness the advent of flexible spectrum/grid reconfigurable optical add drop multiplexers (ROADMs). The pass band of these next generation ROADMs can be varied depending on the spectral width of the incoming signal. With the pass band becoming a variable, spectrum allocation becomes an added constraint to the currently employed routing and wavelength assignment (RWA) algorithm and hence turns it into a routing, wavelength assignment and spectrum allocation (RWSA) problem. In reality, the future networks will be a mix of “Fixed Spectrum” and “Flexible Spectrum” ROADM nodes. Considering this fact, the paper presents a novel RWSA algorithm. The proposed algorithm is applied on NSFNET and two sample networks—11 nodes, 30 node and the results are presented.     

ROADM全光交换网络关键技术发展与应用展望

介绍了可重构光分插复用器（reconfigurable optical add/drop multiplexer，ROADM）网络的发展历程、ROADM技术方案以及国内ROADM网络的部署情况。全面阐述了ROADM关键技术的发展方向，包括光交叉连接（optical cross-connect，OXC）设备、高维度波长选择开关（wavelength selected switch，WSS）、波长无关/方向无关/竞争无关ROADM （colorless/directionless/contentionless ROADM，CDC-ROADM）、400 Gbit/s FlexGrid ROADM、下一代波长交换光网络（next-generation wavelength switched optical network，WSON2.0）智能控制平面技术。分析了现有ROADM网络应用场景与技术发展趋势，展望了ROADM全光交换网络未来发展前景。     

Stackable ROADMs for minimizing lightpath interference during upgrade of in-service WDM networks

Bidirectional stackable ROADMs (BS-ROADMs) with 3-port optical add/drop multiplexers (OADMs) have been presented for minimizing the lightpath interference during reconfiguration of the ROADMs. The BS-ROADM is constructed by connecting some modules with different wavelengths, and it is reconfigured by adding new modules required in it. The reconfigurations of the BS-ROADMs are done for upgrading the in-service networks to support newly appeared traffic demand. The experimental results presented in this paper clarify that the BS-ROADM can multiplex and demultiplex the wavelengths successfully without limiting the pass-through wavelengths, providing the wavelength transparent networks. The reconfiguration of an in-service BS-ROADM can be made without influencing any lightpath in the network, and this type of BS-ROADMs is used for premium users. However, while adding a new module in comparatively low-cost BS-ROADMs in-service, the transmission break of some lightpaths might be taken place. The investigated transmission break time was limited within recovery time specified in the service level agreement for best-effort transmission, which has strong cost-effectiveness rather than high QoS. This upgradability of the BS-ROADMs adds more flexibility in coarse wavelength division multiplexing networks in terms of scalability and reconfigurability.     

Demonstration of 10 Gbit Ethernet/Optical-Packet Converter for IP Over Optical Packet Switching Network

We developed novel network interfaces, for example 10 Gbit Ethernet to 80 Gbit/s optical-packet (10 GbitE–80 GbitOP) or 80 Gbit/s optical-packet to 10 Gbit Ethernet (80 GbitOP–10 GbitE) converters (collectively called as 10 GbitE/80 GbitOP converters), to connect optical packet switching (OPS) networks with IP technology-based networks. By using newly developed arrayed burst-mode optical packet transmitters/receivers together, the 10 GbitE–80 GbitOP converter at the ingress edge node of the OPS network encapsulates an IP packet into an $80(8lambdatimes 10) {rm Gbit/s}$ dense wavelength division multiplexing (DWDM)-based optical packets and generates an optical label based on a lookup table and the destination addresses of the IP packet. The 80 GbitOP–10 GbitE converter at the egress edge node decapsulates the IP packet from the optical packet and generates a 10 GbitE frame accommodating the IP packet according to a lookup table. By using these network interface devices and OPS system based on multiple optical label processing, we achieved, for the first time, 74-km single-mode fiber transmission, switching, and buffering of $80(8lambdatimes 10) {rm Gbit/s}$ DWDM-based optical packets encapsulating almost 10 Gbit/s IP packets with error-free operation (IP packet loss rate $≪ 10^{-6}$).      

Uniform waveband assignment in optical mesh networks

The cost of an optical network in wavelength division multiplexing (WDM) networks can be reduced using optical reconfigurable optical add/drop multiplexers (ROADMs), which allow traffic to pass through without the need for an expensive optical-electro-optical (O-E-O) conversion. Waveband switching (WBS) is another technique to reduce the network cost by grouping consecutive wavelengths and switching them together using a single port per waveband. WBS has attracted the attention of researchers for its efficiency in reducing switching complexity and therefore cost in WDM optical networks. In this paper, we consider the problem of switching wavelengths as non-overlapping uniform wavebands, per link, for mesh networks using the minimum number of wavebands. Given a fixed band size b _s , we give integer linear programming formulations and present a heuristic solution to minimize the number of ROADMs (number of wavebands) in mesh networks that support a given traffic pattern. We show that the number of ROADMs (or number of ports in band-switching cross-connects) can be reduced significantly in mesh networks with WBS compared to wavelength switching using either the ILP or the heuristic algorithm. We also examine the performance of our band assignment algorithms under dynamic traffic.     

A fully implemented 12 /spl times/ 12 data vortex optical packet switching interconnection network

A fully functional optical packet switching (OPS) interconnection network based on the data vortex architecture is presented. The photonic switching fabric uniquely capitalizes on the enormous bandwidth advantage of wavelength division multiplexing (WDM) wavelength parallelism while delivering minimal packet transit latency. Utilizing semiconductor optical amplifier (SOA)-based switching nodes and conventional fiber-optic technology, the 12-port system exhibits a capacity of nearly 1 Tb/s. Optical packets containing an eight-wavelength WDM payload with 10 Gb/s per wavelength are routed successfully to all 12 ports while maintaining a bit error rate (BER) of 10/sup -12/ or better. Median port-to-port latencies of 110 ns are achieved with a distributed deflection routing network that resolves packet contention on-the-fly without the use of optical buffers and maintains the entire payload path in the optical domain.     

Differential precoder IC modules for 20-and 40-Gbit/s opticalduobinary transmission systems

This paper reports on 20- and 40-Gbit/s differential precoder modules for optical duobinary transmission systems. These precoder modules overcome the speed limit of a conventional precoder by parallel processing. The proposed precoders handle two or four parallel signals before multiplexing with data rates of one-half or one-quarter the transmission bit rate, and the final preceded signal is obtained by multiplexing the precoder output bit by bit, production-level 0.2-μm gate-length GaAs MESFET's were used to fabricate the precoders. The precoders are mounted in an RF package. They successfully performed 20- and 40-Gbit/s precoding for the first time, and the 20-Gbit/s precoder achieved a maximum precoding rate of 22 Gbit/s, which is 76% faster than that of the conventional circuit using the same MESFETs. The 40-Gbit/s precoder performs 40-Gbit/s precoding when combined with a 40-Gbit/s multiplexer unit. Twenty-Gbit/s optical duobinary transmitter and receiver circuits using the 20-Gbit/s precoder module successfully generate fully encoded optical duobinary signal at this rate for the first time. These circuits show a receiver sensitivity of -28.6 dBm for a bit error rate of 1×10^-9     

40-Gbit/s TDM transmission technologies based on ultra-high-speedICs

This paper presents 40-Gbit/s time division multiplexing (TDM) transmission technologies based on 0.1-μm-gate-length InP high electron mobility transistor IC's and a scheme for upgrading toward a terabit-per-second capacity system. A 40-Gbit/s, 300-km, in-line transmission experiment and a dispersion-tolerant 40-Gbit/s duobinary transmission experiment are described as 40-Gbit/s single carrier system applications on dispersion-shifted fiber. An ultra-high-speed receiver configuration using a high-output-power photodiode is introduced to realize fully electrical receiver operation beyond 40 Gbit/s. The high-sensitivity operation of the optical receiver (-27.6 dBm@BER=10^-9) is demonstrated at a data bit rate of 50 Gbit/s for the first time using a unitraveling carrier photodiode. A dense wavelength division multiplexing (DWDM) system operating up to terabits per second can be easily realized on a zero-dispersion flattened transmission line using ultra-high speed TDM channels of 40 Gbit/s and beyond. An experiment demonstrates 1.04-Tbit/s DWDM transmission based on 40-Gbit/s TDM channels with high optical spectrum density (0.4 bit/s/Hz) without dispersion compensation     

Optical beat-induced crosstalk of an acousto-optic tunable filterfor WDM network application

Acousto-optic tunable filters (AOTF) using TE-TM mode conversion are attractive for wavelength routers, such as WDM add/drop multiplexers or WDM cross-connect switching fabrics, due to their multichannel selectivity. However, their multichannel selection creates optical beat-induced crosstalk, the so called “coherent crosstalk”, due to the interaction of the lightwave with several acoustic waves. This paper evaluates the transmission characteristics of WDM systems employing AOTF's. First, we develop an analytical model of coherent crosstalk based on the coupled mode theory. Next, we examine coherent crosstalk induced BER degradation both theoretically and experimentally for optical WDM systems and show that the analytical studies well support the experimental results. Finally, maximum AOTF cascade number is estimated based on these results for WDM based wavelength routing networks     

基于光学倍频技术的WDM-ROF-PON系统设计

设计了一种将光载无线技术融合于波分复用无源光网络结构的系统。在发射端,系统采用光学倍频技术生成40GHz光毫米波载波,加载2.5Gbit/s的基带数据信号,下行链路传输性能良好且受色散影响小;在接收端,利用光波重用技术从下行信号中提取上行光载波,加载2.5Gbit/s上行基带数据信号。采用光学倍频技术降低了毫米波生成成本,提高了系统的实用性。     

简化的ROADM模块及其在传送网络升级改造中的应用

首先介绍了现在流行的实现动态可重新配置光上下路复用器(ROADM)模块的解决方案,然后提出了一种简化的ROADM模块和网络结构,接着探讨了它在传送网络升级改造中可能的应用。该方案可用于提高新老设备的利用率,解决峰值时间和各站点间通信堵塞问题。文章还提出了一种用简化的ROADM实现环间业务动态调度的方法。文章所建议的ROADM模块具有成本低、对网络中其它信号干扰小等优点。     

Terabit Transmission at 42.7-Gb/s on 50-GHz Grid Using Hybrid RZ-DQPSK and NRZ-DBPSK Formats Over 16 × 80 km SSMF Spans and 4 Bandwidth-Managed ROADMs

We demonstrate for the first time the use of asymmetric-bandwidth interleaver-based reconfigurable optical add-drop multiplexer (ROADM) to transmit 42.7-Gb/s channels on a 50-GHz grid. Differential binary phase shift keyed (DBPSK) format was used on the wide passband side and differential quadrature phase shift keyed (DQPSK) format was used on the narrow passband side of the ROADM. 25 channels with an aggregate capacity of 1-Tb/s were transported over 1280-km of standard single-mode fiber (SSMF) including 4 ROADMs.     

Reconfigurable Optical Add‐Drop Multiplexer Using a Polymer Integrated Photonic Lightwave Circuit

We have developed a fully functional reconfigurable optical add‐drop multiplexer (ROADM) switch module using a polymer integrated photonic lightwave circuit technology. The polymer variable optical attenuator (VOA) array and digital optical switch array are integrated into one polymer PLC chip and packaged to form a 10‐channel VOA integrated optical switch module. Four of these optical switch modules are used in the ROADM switch module to execute 40‐channel switching and power equalization. As a wavelength division multiplexer (WDM) filter device, two C‐band 40‐channel athermal arrayed waveguide grating WDMs are used in the ROADM module. Optical power monitoring of each channel is carried out using a 5% tap PD. A controller and firmware having the functions of a 40‐channel switch and VOA control, optical power monitoring, as well as TEC temperature control, and data communication interfaces are also developed in this study.     

Demonstration of RSOA‐Based 20 Gb/s Linear Bus WDM‐PON with Simple Optical Add‐Drop Node Structure

We demonstrate a linear bus wavelength‐reused gigabit wavelength‐division multiplexing passive optical network (WDM‐PON) with multiple optical add‐drop nodes. A commercially available reflective semiconductor optical amplifier‐based WDM‐PON has a sufficient power budget to provide multiple optical add/drop nodes in 16 WDM channels. Sixteen 1.25 Gb/s WDM channels are successfully transmitted over 20 km of single‐mode fiber with four optical add/drop multiplexers, even with 32 dB reflection and chromatic dispersion in the link.     

Key technologies for terabit/second WDM systems with high spectralefficiency of over 1 bit/s/Hz

To fully utilize a limited gain bandwidth of about 35 nm (4.4 THz) in an erbium-doped fiber amplifier, an increase in signal spectral efficiency is required. In this paper, we investigate the key technologies to achieve terabit/second wavelength-division multiplexing (WDM) systems with over 1 bit/s/Hz spectral efficiency. Optical duobinary signals, which have narrower optical spectra than conventional intensity modulation signals, were applied to such dense WDM systems. The measured minimum channel spacing for 20-Gbit/s optical duobinary signals was 32 GHz and a spectral efficiency of over 0.6 bit/s/Hz was reached. By using polarization interleave multiplexing, spectral efficiency was expected to reach 1.2 bit/s/Hz in an ideal case with no polarization dependencies along the transmission lines. In such ultradense WDM systems with narrower channel spacing, stabilizing the wavelengths of laser diodes is an important issue for achieving stable operation over long periods. To do this, we developed a simple and flexible wavelength stabilization system which uses a multiwavelength meter. The wavelengths for 116 channels with 35-GHz spacing were stabilized within ±150 MHz. The stabilization system is applicable to ultradense WDM signals with a spectral efficiency of over 1 bit/s/Hz by employing wavelength interleave multiplexing and an optical selector switch. On the basis of these investigations, we demonstrated a 2.6-Tbit/s (20 Gbit/s×132 channels) WDM transmission by using optical duobinary signals. In addition, 1.28-Tbit/s (20 Gbit/s×64 channels) WDM transmission with a high spectral efficiency of 1 bit/s/Hz was achieved by using polarization interleave multiplexing     

160 Gb/s variable length packet/10 Gb/s-label all-optical label switching with wavelength conversion and unicast/multicast operation

We report on the first demonstration of all-optical label switching (AOLS) with 160 Gb/s variable length packets and 10 Gb/s optical labels. This result demonstrates the transparency of AOLS techniques from previously demonstrated 2.5 Gb/s to this 160 Gb/s demonstration using a common routing and packet lookup framework. Packet forwarding/conversion, optical label erasure/re-write and signal regeneration at 160 Gb/s is achieved using a WDM Raman enhanced all-optical fiber cross-phase modulation wavelength converter. It is also experimentally shown that this technique enables packet unicast and multicast operation at 160 Gb/s. The packet bit-error-rate is measured for all optical label switched 16 /spl times/ 10 Gb/s channels and error free operation is demonstrated after both label swapping and packet forwarding.