Split spectrum: a multi-channel approach to elastic optical networking

This paper introduces Split Spectrum, which enhances elastic optical networking by splitting a bulk traffic demand into multiple channels, when a single-channel transmission is prohibited by distance or spectrum availability. We performed transmission simulations to determine the maximum reach as a function of modulation format (dual polarization BPSK, QPSK, 16QAM), baud-rate (from 5 to 28 GBd), and number of ROADMs, for a Nyquist WDM super-channel with subcarrier spacing equal to 1.2 x baud-rate. Performance evaluation on two representative topologies shows that, compared to the previously proposed elastic optical networking, Split Spectrum doubles the zero-blocking load and achieves 100% higher network spectral efficiency at zero-blocking loads as a result of extended transmission distance and efficient utilization of spectrum fragments. (C) 2012 Optical Society of Americ

符号化可能なネットワークにおける高信頼経路設計方式

電気通信大学201

Optical flow switched networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 253-279).In the four decades since optical fiber was introduced as a communications medium, optical networking has revolutionized the telecommunications landscape. It has enabled the Internet as we know it today, and is central to the realization of Network-Centric Warfare in the defense world. Sustained exponential growth in communications bandwidth demand, however, is requiring that the nexus of innovation in optical networking continue, in order to ensure cost-effective communications in the future. In this thesis, we present Optical Flow Switching (OFS) as a key enabler of scalable future optical networks. The general idea behind OFS-agile, end-to-end, all-optical connections-is decades old, if not as old as the field of optical networking itself. However, owing to the absence of an application for it, OFS remained an underdeveloped idea-bereft of how it could be implemented, how well it would perform, and how much it would cost relative to other architectures. The contributions of this thesis are in providing partial answers to these three broad questions. With respect to implementation, we address the physical layer design of OFS in the metro-area and access, and develop sensible scheduling algorithms for OFS communication. Our performance study comprises a comparative capacity analysis for the wide-area, as well as an analytical approximation of the throughput-delay tradeoff offered by OFS for inter-MAN communication. Lastly, with regard to the economics of OFS, we employ an approximate capital expenditure model, which enables a throughput-cost comparison of OFS with other prominent candidate architectures. Our conclusions point to the fact that OFS offers significant advantage over other architectures in economic scalability.(cont.) In particular, for sufficiently heavy traffic, OFS handles large transactions at far lower cost than other optical network architectures. In light of the increasing importance of large transactions in both commercial and defense networks, we conclude that OFS may be crucial to the future viability of optical networking.by Guy E. Weichenberg.Ph.D

Future benefits and applications of intelligent on-board processing to VSAT services

The trends and roles of VSAT services in the year 2010 time frame are examined based on an overall network and service model for that period. An estimate of the VSAT traffic is then made and the service and general network requirements are identified. In order to accommodate these traffic needs, four satellite VSAT architectures based on the use of fixed or scanning multibeam antennas in conjunction with IF switching or onboard regeneration and baseband processing are suggested. The performance of each of these architectures is assessed and the key enabling technologies are identified

On-board B-ISDN fast packet switching architectures. Phase 1: Study

The broadband integrate services digital network (B-ISDN) is an emerging telecommunications technology that will meet most of the telecommunications networking needs in the mid-1990's to early next century. The satellite-based system is well positioned for providing B-ISDN service with its inherent capabilities of point-to-multipoint and broadcast transmission, virtually unlimited connectivity between any two points within a beam coverage, short deployment time of communications facility, flexible and dynamic reallocation of space segment capacity, and distance insensitive cost. On-board processing satellites, particularly in a multiple spot beam environment, will provide enhanced connectivity, better performance, optimized access and transmission link design, and lower user service cost. The following are described: the user and network aspects of broadband services; the current development status in broadband services; various satellite network architectures including system design issues; and various fast packet switch architectures and their detail designs

Optical phase conjugation in fiber-optic transmission systems

As the data rate of long-haul transmission links is increased, the design and realization of the transmission link becomes more difficult. As a result, more sophisticated methods are required to improve the transmission quality. The robustness of a transmission link can be increased and its structure greatly simplified by the use of mid-link optical phase conjugation (OPC). OPC is a promising technology to compensate for deterministic, phase related impairments (i.e. the Kerr effect and chromatic dispersion) in long-haul transmission systems. This thesis assesses the regenerative capabilities of OPC for the compensation of distortions that occur in modern transmission systems. The focus of the research is on transmission systems where OPC is employed to compensate for both chromatic dispersion and nonlinear impairments. The dispersion map (i.e. the dispersion as a function of the transmission distance) of such a transmission system is completely different from that of a conventional transmission system. The accumulated dispersion along the link of an OPCbased transmission system is significantly higher than that of a conventional transmission system. We investigated the influence of the dispersion map of OPC on nonlinear impairments using the non return-to-zero amplitude-shift-keying (NRZ-ASK) modulation format. As a result, it is shown that the peak powers that occur in the OPC transmission system are at a 10-Gbit/s/channel data rate significantly higher than the peak powers that occur in a conventional transmission system. The higher peak powers in the OPC based transmission system lead to an increased self-phase modulation (SPM) penalty. Through phase conjugation most of the SPM impairments are compensated for. However, when multiple wavelength division multiplexed (WDM) channels at narrow channel spacing are used for transmission, cross-phase modulation (XPM) is the dominating transmission impairment. Although XPM is principally a deterministic distortion, it must be treated as non-deterministic due to the dispersion of the transmission link. With simulations and experiments we show that because of this, the XPM compensation through OPC is marginal. At a 40 Gbit/s data rate, the peak powers that occur in the OPC-based transmission system are similar to those that occur in the conventional transmission system. In 40 Gbit/s WDM transmission systems the influence of XPM is relatively low. These transmission systems are rather limited by intra-channel nonlinear impairments such as SPM, intrachannel XPM (IXPM) and intrachannel FWM (IFWM). We show experimentally that in this case, the performance of the OPC transmission system is better than that of the conventional transmission system. When OPC is used to compensate for the chromatic dispersion, the OPC must be placed in the middle of the transmission link. This technique is often referred to as "midlink OPC". However, in some transmission links it is not possible to place the OPC exactly in the middle. Therefore, several configurations with a transmission length of 700 km to 900 km were assessed where the OPC was placed 100 km from the middle of the transmission link. In this experiment practically no bit-error ratio (BER) degradation was observed in the off-center configuration. Recently, strong interest has been shown in phase-shift keying modulation (PSK) formats such as differential phase-shift-keying (DPSK). DPSK’s main advantages over ASK are that it is more robust to narrowband optical filtering and has a 3 dB higher sensitivity in combination with balanced detection. However, unlike ASK signals PSK signals can be distorted by nonlinear phase noise (NPN). For long-haul transmission systems, the impact of NPN is so severe that the performance of DPSK is in some cases even worse than that of ASK. The impact of nonlinear phase noise is studied for 10.7-Gbit/s DPSK in an 800-km transmission link. In this experiment it is shown that impairments due to nonlinear phase noise can be significantly reduced using optical phase conjugation. The dependence of the location of the OPC within the transmission link is assessed as well. Allowing a penalty of 1 decade in BER from the optimum, the OPC-unit can be varied over a wide range, from nearly 1/3 to 2/3 of the transmission link. The combination of mid-link OPC is assessed with 21.4-Gbit/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) in an ultra long-haul transmission experiment. Error-free transmission after FEC is realized over 10,200 km for all 22 WDM channels. In this experiment, a single OPC-unit is used in the middle of the link to compensate for an accumulated chromatic dispersion of over 160,000 ps/nm. Along the transmission line, the dispersion accumulates in this experiment to more than 80,000 ps/nm. This is significantly higher than the maximum accumulated dispersion in the conventional transmission system (approximately 3,000 ps/nm). The high accumulated dispersion results in an extreme overlap of the pulses along the transmission line. With this experiment we show that despite the high dispersion, the feasible transmission distance of the OPC based transmission system is 44% greater than that obtained in the conventional transmission system. By doubling the data rate and keeping the 50-GHz channel spacing, a 0.8-bit/s/Hz spectral efficient WDM transmission system is realized. At 42.8-Gbit/s RZ-DQPSK, transmission over 5,000 km was realized with mid-link OPC. Compared to the feasible transmission distance obtained at 21.4-Gbit/s, the feasible transmission distance is reduced by about 50%. This reduction of transmission distance with 50% corresponds to the 3-dB OSNR penalty that is present between 21.4-Gbit/s and 42.8-Gbit/s RZ-DQPSK in the back-toback configuration. For the conventional transmission system, a greater reduction in the feasible transmission distance (factor of 2.4) is measured due to increased penalties that result from a combination of self phase modulation and nonlinear phase noise. Comparing the feasible transmission distance of the OPC to the conventional transmission system an improvement of 60% is observed in this experiment

The Third NASA Goddard Conference on Mass Storage Systems and Technologies

This report contains copies of nearly all of the technical papers and viewgraphs presented at the Goddard Conference on Mass Storage Systems and Technologies held in October 1993. The conference served as an informational exchange forum for topics primarily relating to the ingestion and management of massive amounts of data and the attendant problems involved. Discussion topics include the necessary use of computers in the solution of today's infinitely complex problems, the need for greatly increased storage densities in both optical and magnetic recording media, currently popular storage media and magnetic media storage risk factors, data archiving standards including a talk on the current status of the IEEE Storage Systems Reference Model (RM). Additional topics addressed System performance, data storage system concepts, communications technologies, data distribution systems, data compression, and error detection and correction