A 150-km Repeaterless Undersea Lightwave System Operating at 1.55um

A repeaterless undersea cable system spanning 150 km between a shore site and an off-shore floating platform is to be installed early in 1985. The system uses single-mode fibers to carry data at a line rate of 3.088 Mbit/s. Laser transmitters operating at 1.55 μm and p-i-n receivers complete the optical system. This paper discusses system parameters and performance, and both terminal and undersea equipment.     

A 150-km repeaterless undersea lightwave system operation at 1.55 µm

A repeaterless undersea cable system spanning 150 km between a shore site and an off-shore floating platform is to be installed early in 1985. The system uses single-mode fibers to carry data at a line rate of 3.088 Mbit/s. Laser transmitters operating at 1.55 μm and p-i-n receivers complete the optical system. This paper discusses system parameters and performance, and both terminal and undersea equipment.     

Recent progress in amplified undersea systems

The advent of the optical amplifiers has removed the loss limitation of the fiber in the conventional undersea systems using 3R (retiming, reshaping, regenerating) repeaters, and it has introduced new design criteria for the undersea lightwave systems. The accumulation of the small impairment factors that was negligible in the conventional system becomes significant to determine the transmission performances of the amplified system. The fiber nonlinearity is a distinctive limitation factor that dominates the transmission performance of the amplified system, although it was not a limitation factor in the conventional system. This paper describes the recent progress of the undersea lightwave cable systems employing optical amplifier repeaters. The limitation factors and the polarization dependent characteristics of the amplified system are described. The system demonstrations with conventional IM-DD technology are presented using both recirculating loop and straight fiber transmission line. The system maintenance method is also explained briefly. Future technologies adopting the WDM or the optical solitons are also discussed     

The glass necklace [FLAG submarine fibre-optic link]

The longest ever man-made structure is being assembled in the world's most ambitious undersea lightwave communications system. When completed in 1997, the system will link Great Britain and Japan by a complex undersea optical-fiber cable that will span 27,300 km-more than two-thirds of the Earth's circumference. Called the fiber-optic link around the globe (FLAG), it will snake in eight sections through the Atlantic Ocean, the Mediterranean and the Red Seas, the Indian Ocean, and the Pacific Ocean. The authors describe how the backbone of FLAG is third-generation transoceanic optical-fiber cable technology     

Optical amplifiers transform long-distance lightwavetelecommunications

Optical amplifiers and wavelength-multiplexing technology are transforming lightwave communications by providing cost-effective upgrades that will increase immensely the transmission capacity of long-distance telecommunications networks. A new generation of undersea cable systems using fiber optical amplifiers as repeaters has been developed for transoceanic applications, yielding a capacity almost ten times larger than conventional systems using opto-electronic regenerators. Terrestrial long-haul networks will benefit significantly from amplified wavelength-multiplexed transmission systems designed to access the large inherent bandwidth in the installed fiber. Successful deployment of these advanced systems requires a thorough understanding of optical amplifiers and the optical fiber medium, as their requirements interrelate through optical bandwidth, noise, dispersion, optical nonlinearities, and their impact on signal transmission. While the first commercial WDM amplified lightwave systems are deployed for point-to-point applications, optical transparency and wavelength multiplexing will be exploited for networking leading to the higher functionality and improved cost-effectiveness expected of photonic networks     

Effect of natural radioactivity on optical fibers of underseacables

For undersea cables radiation doses between 2.5 and 25 rad are to be expected during a working life of 25 years. The majority of previous investigations of the radiation sensitivity of optical fibers, however, apply dose rates ≳1 rad/s and total dose values ≳3×10 ³ rad. The present paper describes ⁶⁰Co irradiations of a Ge-doped single mode fiber with dose rates between 10 ^-4 and 20 rad/s. Expected loss increase of an undersea optical fiber cable at 1550 nm wavelength with a temperature of 2°C is derived by three different methods. The most comfortable and reliable one, the `dose rate transformation method', yields, for example, a loss of only 0.0244 dB/100 km after 25 years of irradiation with a dose rate of 0.4 rad/s. This method could be the basis of a standard test procedure for the effect of natural radioactivity on optical fibers for very long repeaterless terrestrial and undersea cables     

Undersea fiber cable technology

Compared with the conventional coaxial undersea cable systems, an optical fiber undersea cable system has a great technical and economical advantage. It is also suitable for digital transmission. In this paper, the optical fiber undersea cable technology (including optical fiber cables and repeaters), which is now in the research and development stage in several countries, is reviewed.     

Active feedback lightwave receivers

This paper describes new p-i-n-FET lightwave receivers that achieve high sensitivity without signal integration, and dynamic ranges large enough that they cannot be saturated by present lightwave transmitters. IC versions can be realized inexpensively in standard fine-line NMOS, CMOS, or GaAs IC technologies, and thus are suitable for loop-plant, local-area-network, and data link applications, as well as long-haul transmission applications. These receivers also can readily be designed for bit-rates in excess of 1 Gbit/s for high-capacity systems. In addition, these receivers can be implemented on the same IC as other system functions, e.g., for single-chip lightwave regenerators and lightwave modems, and, eventually, for microprocessors with on-chip optical communications ports.     

Optical undersea cable systems trends

This paper reviews the evolution of undersea cable technology from the telegraph cables of the mid-nineteenth century to the optical undersea cables of today. Future systems will use optical fiber amplifiers which offer significant technical and economic advantages. Consequently, emphasis is placed on problems associated with the accumulation of small, second-order effects in long lengths of optical fiber and, specifically, their impact on the 5-Gb/s optically amplified transoceanic undersea systems scheduled to be deployed in 1995. Technology options for achieving further capacity increases, among them the use of optical solitons, and trends toward networked undersea cable systems with automatic restoration features are described     

Technology 1993-telecommunications

Significant events during 1992 are highlighted. Communication technologies began merging, with cable TV offering telephone service and telecommunication companies offering TV. Wireless personal communication systems (PCSs) got the green light when the 1992 World Administrative Radio Conference designed frequency bands for future mobile communications services, with provisions for such services to be handled via low-Earth-orbiting satellites, and the US Federal Communication Commission allocated frequencies in the 2 GHz band to the deployment of several emerging technologies, including PCSs. Multimedia communication took off with the introduction of new services. In optical communication, erbium-doped fiber amplifiers were installed in the world's longest repeaterless undersea link. Strained-layer multi-quantum-well lasers received increasing attention, due to the improved system and device properties they offer. Research on cheap optical interconnects and packages gained momentum     

Trends in U.S. Broad-Band Fiber Optic Transmission Systems

Fiber optic media are rapidly penetrating the telecommunications network. They are used as undersea and terrestial trunk lines, central-office loops, optical data links, and will eventually be included within the distribution plant which connects directly into individual premises. The rapid implementation of lightwave systems is occurring because the high bandwidths and low losses of optical fibers enable broad-band communication services to be provided between widely spaced repeaters and also allows users to upgrade currently installed systems to meet future needs. This paper will describe current applications and show how future trends will depend upon the continuing evolution of lightwave components and optical fiber designs.     

CTNE Undersea Lightwave Inter-Island System

The world's first deep-water undersea repeatered lightwave cable system will be installed in the Canary Islands in 1985. The threerepeater 120-km 1.3-μm system will be used initially to prove-in the SL Undersea Lightwave System and later to provide commercial service to CTNE.     

CTNE undersea lightwave inter-island system

The world's first deep-water undersea repeatered lightwave cable system will be installed in the Canary Islands in 1985. The three-repeater 120-km 1.3-μm system will be used initially to prove-in the SL Undersea Lightwave System and later to provide commercial service to CTNE.     

Future 1.55-µm undersea lightwave systems

Future undersea lightwave systems will very likely employ 1.55-μm lightwave technology. This paper discusses the technical trends for such systems, and outlines the major options available for their design. Repeater spacings for these systems can be over 100 km, almost double the spacing for present 1.3-μm systems.     

Review of the Depressed Cladding Single-Mode Fiber Design and Performance for the SL Undersea System Application

High-capacity undersea cable systems based on optical transmission over single-mode lightguides offer tremendous economic advantage over coaxial cable technology due to their combined high-bit-rate long repeater spacing potential. However, very stringent requirements for the lightguide transmission medium properties must be met in order to realize the performance goals of such systems. This paper will review the depressed index cladding single-mode fiber design and its resultant performance. The ability to simultaneously realize excellent optical, mechanical, and dimensional properties in lightguides of this type fabricated using the Modified Chemical Vapor Deposition (MCVD) process has resulted in their use in the AT&T SL system to be used in TAT8.     

Physical Design of the SL Repeater

SL undersea fiber-optic cable allows for the installation of multiple pairs of fibers in the same cable. Using the same high-pressure repeater housing as used in previous undersea systems (and thereby accruing the benefits of no tooling costs and proven handling methods), we are able to mount six optical regenerators. This group of regenerators will dissipate approximately 30 W in service. Previous undersea repeaters dissipated approximately 8 W and achieved a maximum internal temperature of 5° C above the repeater ambient. That might imply a temperature of 20° C above ambient for the SL repeater, which would be intolerably high for reliable undersea performance and longevity. The main thrust of the SL design was to lower this temperature rise. We have achieved a design which is capable of dissipating 30 W with only 4°C temperature rise. This paper describes the design steps necessary to achieve this result and examines the overall repeater structure showing its special design features for accommodating fiber sealing and jointing.     

The SL Undersea Lightwave System

The SL Undersea Lightwave System is a large capacity digital fiber-optic transmission system capable of spanning the world's largest oceans and seas. The system is now being manufactured for use in telecommunications systems planned for the Atlantic and Pacific Oceans. In this paper we will discuss how the risks associated with using relatively new lightwave technology were minimized to design a digital undersea communication system which excels in reliability, availability, and performance.     

An algebraic approach to the unequal-spaced channel-allocationproblem in WDM lightwave systems

To reduce four-wave-mixing crosstalk in high-capacity, long-haul, repeaterless, wavelength-division multiplexing (WDM) lightwave systems, the use of unequally spaced channels has been proposed. Instead of being solved by integer linear programming, the unequal-spaced channel-allocation problem is treated by constructing suitable optical orthogonal codes in optical code-division multiple-access (CDMA). An “algebraic” framework and three algorithms on finding the frequency locations of unequally spaced WDM channels are introduced, where the constructions are based on generating optical CDMA codewords with a predetermined pulse separation and “aperiodic” autocorrelation sidelobes no greater than one. The algorithms potentially provide a fast and simple alternative to solve the problem, besides the proposed computer-search method     

Frequency division multiplexed optical networks using heterodynedetection

The optical heterodyne process is described. Because the best attainable system gain (transmitter power divided by receiver sensitivity) is only about 50 dB for lightwave systems, as compared with values approaching 100 dB at radio frequencies, it is extremely important in building an optical network (such as a local area network, or LAN) to minimize excess tap losses. It is shown that a star coupler provides a nearly ideal means for interconnecting a multiterminal network. Three areas in which problems unique to optical systems have been discovered are discussed. Theses are transmitters for coherent optical systems, optical frequency determination and control, and polarization control and optical receivers. Experimental progress is briefly discussed     

光纤外护套绝缘故障的监测

为了保障长途海底光缆的运行可靠性，需要尽早发现潜在的故障。本文介绍了一种监测海底通讯光缆外护套电绝缘性能的方法。该方法使用微控制器控制高压信号源，并同时精确控制测试电流。使用这种方法可以早期发现海底光缆的损伤。