Optical Cable System Research Articles

Polarization diversity techniques for the use of coherent optical fiber submarine cable systems

Recent research and development work on coherent transmission systems, with emphasis on its application to optical-fiber submarine cable systems, are described. The authors demonstrated the feasibility of a polarization diversity scheme in a laboratory environment as well as in the first sea trial of a coherent frequency-shift-keying (FSK) system. The authors propose a novel external cavity laser module and a polarization coupling/dividing module in order to improve the system performance. The polarization fluctuation speed in optical-fiber submarine cable reaches 50 Hz in the worst case, and the polarization diversity scheme is a simple and very powerful technique under such polarization fluctuation conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optical fiber submarine cable systems

Optical fiber submarine cable systems especially developed for international systems throughout the world are reviewed, and the future technologies for optical fiber submarine cable systems are discussed. The discussion covers: system design; cable design and the fiber used; mechanical design of submarine optical repeaters; branching repeaters; repeater circuits; reliability; terminal equipment; repeater supervisory systems; initial system applications; and future trends. >

Novel coherent heterodyne optical time domain reflectometry for fault localization of optical amplifier submarine cable systems

A coherent, heterodyne-detection, optical time-domain reflectometry technique suitable for an all-optical repeater system is proposed. Rayleigh backscatter measurement through a 309-km bidirectional optical transmission line with six cascaded in-line semiconductor laser amplifiers is demonstrated using this technique. The possibility of fault localization on an optical amplifier system with optical isolators is shown.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Three Dimensional Dynamic Analysis for Laying and Recovery of Optical Submarine Cables

The author has developed two types of cable laying simulation programs based on three dimensional dynamic analysis method in order to analyze dynamic behavior of cables, repeaters and branching unit during laying and recovery.One is a computer simulation program for laying and recovery of submarine cables with repeaters. This program has following two new functions is addition to conventional cable laying simulation.(1) Slack control laying function. The cable pay-out speed is automatically calculated by internal feed back loop so as to make bottom cable slacks be constant. Using this function, the optimum cable pay -out speed history can be obtained by giving the bottom profile and cable ship speed profile.(2) Tension control laying function. The cable pay-out speed is automatically calculated by internal feed back loop so as to make shipboard tension be constant. The speed error of cable ship measured by 'taut wire' is discussed using this program. This error is exactly analyzed using this tension control laying simulation.The other is a computer program for laying and recovery submarine cables with a cable branching unit. The cable branching unit (BU) is newly installed to the optical submarine cable systems. This newly developed program can analyze dynamic behavior of BU and cables around it, and help to study how to lay BU with sufficient cable slacks and recover it safety.The sea trial was carried out in order to measure hydrodynamic constant of the submarine cable and verify this computer simulation method at the depth of 6000m by attaching sensors to the submarine cable at some intervals. According to the sea trial, the normal drag coefficient Cd was measured to 2.5, andd the cable configuration measured by this experiment was in good agreement with the result of the computer simulation.

First field demonstration of optical submarine cable system using LD-pumped Er-doped optical fibre amplifier

This is a report on the first field demonstration of an optical submarine cable system using an in-line Er-doped optical fibre amplifier pumped by a 1.47μm laser diode. The experiment was performed at an ocean depth of 3000 m. With a maximum optical repeater gain of 20 dB, l.2 Gbit/s intensity-modulated optical signals were transmitted stably during and after installation and also during recovery of the system. Furthermore, the effectiveness of an automatic-gain-control (AGC) scheme proposed for optical amplifiers was confirmed in a practical environment.

Deep sea trial of 1.55 µm optical fibre submarine cable system

The first 6000 m deep sea trial of a 1.55 µm optical fibre submarine cable system was successfully conducted in the Pacific Ocean, near Torishima Island, in January 1988. By using 1.55 µm loss-minimised single-mode fibre cables and submerged fully monolithic Si-IC regenerators with DFB lasers, excellent transmission performances at 140, 280 and 565 Mbit/s were obtained through 150 km repeater spacings, respectively.

Submarine optical fibre cable system applications

The transition from analogue coaxial cable to digital optical fibre submarine systems has required a new technology to be established and complementary technologies to be developed for the design, evaluation and operational support of these new systems. The common design parameter throughout is reliability; not only must the overall system design satisfy the reliability objective but the component parts must be shown to exhibit the necessary low level of failure for this to be achieved.1988 sees the commissioning of TAT-8, the first trans atlantic optical fibre submarine cable system. In addition a number of submarine cable systems linking the UK mainland with other British Islands and Europe will be made available. This paper reviews the current generation of submarine cable systems based on 1.3μm and emerging 1.55μm technologies and discusses the opportunities offered to planners and network operators from developments in networking, optical repeaters and non-silica fibres.

The design and realization of a high reliability semiconductor laser for single-mode fiber-optical communication links

Long-haul trunk telecommunication systems, particularly optical submarine cable systems, have especially demanding reliability requirements. The authors describe how the InGaAsP inverted-rib waveguide (IRW) laser was designed for use as the source for such single-mode systems by minimizing known degradation hazards. The results of an extensive reliability assurance program are summarized. This included wafer validation endurance tests, overstress tests, and package design and life tests. The results of 7 million life-test hours confirm that the IRW laser has extremely good reliability performance. >

High reliability planar-type GaInAs/InP heterostructure avalanche photodiodes

High-temperature, long-term life tests of GaInAs/InP heterostructure avalanche photodiodes have been carried out to establish criteria for high reliability photodetectors in 1.55μm-wavelength optical submarine cable systems. A failure rate of less than 0.2 FIT at 10°C was predicted for the first time with an activation energy of 0.7 eV.

Non-intrusive optical fibre identification using a high-efficiency macrobending ‘clip-on’ optical component

Results of a laboratory experiment are reported in which a non-intrusive optical fibre cable identification system has been implemented by incorporating cable identification data in the transmission systems supervisory channel. These data are accessed by a novel optical component which ‘clips-on’ to the installed optical line plant and does not require access to the end of the fibre, while its insertion loss is within the limits defined by the systems optical power budget.

Experience with Operational Fiber Optic Systems in the Hong Kong Telephone Network

This paper presents an overview of internal and external plant aspects of the optical cable transmission systems applied by Hong Kong Telephone since 1981.

Reliability of the OS-280M Optical Submarine Repeater

The development phase of the OS-280M optical submarine cable system is finished, and currently the mass production lines for the system are arranged so as to satisfy the specific performances and the reliability requirements for the TPC-3 system within its system life of 25 years. KDD developed the reliability assurance system of the repeater components, which began three years ago. In this paper, we will introduce the reliability design of the OS-280M system and will report on the reliability test results obtained until the present time. In conclusion, it will be demonstrated that all of repeater components, i.e., optical semiconductor devices, monolithic IC's, several kinds of optical devices, and conventional components could satisfy the reliability requirements for the OS-280M system.

Secure Splice Closures for Optical Fiber Systems

The problems of splice closure are discussed briefly and the options available for optical fiber cable systems are reviewed. It is concluded that for long-haul point-to-point cables, absolute security is paramount, and that for these, welded splice closures should be used. For optical fiber cables in local distribution networks, however, closures which can easily be reentered are needed. This requirement can only be met with some kind of mechanical closure. The security of these is considered inadequate for nonpressurized optical fiber networks. It is concluded that the use of mechanical closures must be supported by a satisfactory test method to confirm that they are sealed after each reentry. Conventional pressure testing of complete closures is considered to be too unreliable and slow for the purpose. A new double-seal closure system is described which allows the integrity of closures to be tested in seconds using a purpose-designed test device. The double-seal system is being used for the optical fiber distribution system being installed in the city of London by Mercury Communications Ltd.

Self-core-alignment arc-fusion splicer based on a simple local monitoring method

We have developed an arc-fusion splicer with a self-core-alignment function based on cladding-mode-leakage light power monitoring that incorporates a microprocessor, piezoelectric elements, and a photoreceiver with high sensitivity, for monitoring the leakage light power without bending the receiving fiber. The design and the performance of the splicer are presented. Using the splicer, we successfully demonstrate the splicings of single-mode fibers in a repeater section of an experimental optical submarine cable transmission system. The required time for one splicing including the self-core-alignment process is only 50 s and we have obtained extremely good results with an average splice loss of 0.035 dB for 100 splices at the far end of a 30-km-long single-mode fiber connected with a repeater.

Recent advances in submarine optical fiber cable transmission systems in Japan

Submarine optical fiber cable transmission systems are promising successors to existing submarine coaxial cable systems. This paper will review the history and the state of the art of the submarine optical fiber cable transmission technology, and the submarine optical fiber cable transmission systems named FS-400M and OS-280M being developed by NTT and KDD, respectively, in Japan.

Determination of installation cable size and the ratio of common fibers to total fibers in subscriber optical fiber cable network

AbstractTo construct an efficient subscriber optical fiber cable network, a highly economical and versatile distribution method is needed. This paper clarifies a technique in which by determining the installation cable size of feeder system and the ratio of common fibers to total fibers, a balance between the service requirement and cost is obtained.First, gamma distribution, practically used for metal cables, is applied to the demand forecast error distribution and the relation between the number of fibers and the ratio of common fibers to total fibers, which is required to obtain the desired equipment reliability, is clarified. Next, the relation between the cross‐connecting probability is determined and utilizing the ratio of common fibers, the cost function of optical cable system is derived. Here, both the cable installation cost and cross‐connection cost are considered. These two factors are combined and a design method of installation cable size and the ratio of common fibers to total fibers is clarified. This method ensures the desired equipment reliability and is the most economical one. Using this method and assuming all the various costs, it is clarified that for high cross‐connection cost, a cable having a large number of fibers should be installed and the cable network construction having comparatively low ratio of common fibers to total fibers is desirable. When the cross‐connection cost is less, the installation cable having a smaller number of fibers and a higher ratio of common fibers to total fibers is desirable. Moreover, with these results in mind, an economical subscriber optical fiber cable network construction is proposed.

A design and experimental results of the OS-280M optical submarine repeater circuits

This paper describes the design philosophy and the experimental results of the optical submarine repeater for the OS-280M optical fiber submarine cable system to be installed across the ocean. This repeater which employs the information rate of 280 Mbit/s, the optical wavelength of 1.3 μ, and is implemented with monolithic ICs, features high reliability, long repeater spans, and the supervisory systems. The test results show that the average optical output power is - 1.4 dBm for the mark density of 1/2, the minimum average power of the optical input for the BER 10 is about -38 dBm at the room temperature, and other specifications are also well satisfied.

Design and Test Results of an Optical Fiber Feedthrough for an Optical Submarine Repeater

A new hermetic sealing structure is described in which optical fibers are metal coated and sealed off. The gap between the fibers and the metal pipe is filled with solder. The sealing structure is used as a feedthrough of a repeater for a long-haul optical fiber submarine cable system. According to theoretical study, airtightness was found reliable for a long period of time by utilizing a self-seal effect operating at the time of pressurizing through the structure where circumferences of fibers are soldered for sealing. Manufacture on trial proved that perfect airtightness was achieved even after a heat cycle test (60°C- -10°C) and shock test (50 G). The incremental loss due to temperature changes in the range from 60°C to - 10°C was less than 0.015 dB and an incremental loss of 0.06 dB or less was observed when the structure was pressurized by 800 kg/cm2, however no residual loss could be found.

Design and Experimental Results of the OS-280M Optical Submarine Repeater Circuits

This paper describes the design philosophy and the experimental results of the optical submarine repeater for the OS-280M optical fiber submarine cable system to be installed across the ocean. This repeater which employs the information rate of 280 Mbit/s, the optical wavelength of 1.3 μm, and is implemented with monolithic IC's, features high reliability, long repeater spans, and the supervisory systems. The test results show that the average optical output power is - 1.4 dBm for the mark density of 1/2, the minimum average power of the optical input for the BER 10 is about -38 dBm at the room temperature, and other specifications are also well satisfied.

Repeater Fault Location for a Submarine Optical Fiber Cable Transmission System

This paper introduces a repeater fault location system for a repeated submarine optical fiber transmission system of 400 Mbits/ s at 1.3μm. The repeater fault location system is used in an out-of-service test. The fault locator transmits a test signal via a main optical fiber line, in order to make a loop-back path in one of the repeaters for returning the test signals via another main optical fiber line and to measure the bit error rate (BER) of the interrogated repeater. The test signal is a kind of pseudorandom signal that includes a low frequency component, which is assigned to the repeater as a supervisory frequency tone (SVT) signal. The BER is measured by counting the number of low frequency signal phase inversions in a time. This paper first describes the test signal generating method, SVT frequency allocation, and the filter design installed in a repeater. Next, there is a discussion of how the capability of the repeater fault locator has been experimentally verified by using two submarine repeaters, including four regenerative repeater units and three submarine optical fiber cables. As a result, a BER of less than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5 \times 10^{-6}</tex> is accurately measured.