Bangladesh Submarine Cable Company (BSCCL)

INTRODUCTION:

Bangladesh Submarine Cable Company (BSCCL) is a Telecommunications infrastructure service provider primarily through the international Submarine Cable and domestic high capacity optical fiber network. Thus, the service provided by BSCCL represents the gateway communication between Bangladesh and the rest of the world. Emerging in July 2008 from BTTB (Bangladesh Telegraph & Telephone Board)’s submarine cable project, BSCCL presently handles Bangladesh’s lone submarine cable called the SEA-ME-WE-4 submarine cable and represents our country in the SMW-4 international cable consortium. By providing submarine cable Bandwidth through the SEA-ME-WE-4 cable system BSCCL is contributing to the revenue earning of the Government of Bangladesh. BSCCL is one of the growing companies in the Telecom sector in the country. It is a leading company in implementing National ILDTS & ICT policy to develop modern tele network in Bangladesh. The submarine cable network is expected to be the main telecommunications infrastructure for “Digital Bangladesh” by the year 2021 and BSCCL is going to play a major role in this regard.

Related Terminologies:

 DWDM: Dense Wavelength Division Multiplexing

 SDH: Synchronous Digital Hierarchy

 IIG: International Internet Gateway

 IGW: International Gateway

 ICX: Inter Connection Exchange

 SEA-ME-WE-4: South East Asia-Middle East-Western Europe-4

 TAT: Trans Atlantic Telephone

 STM: Synchronous Transfer Module

BSCCL:

Bangladesh Submarine Cable Company (BSCCL) is a fiber optic submarine cable telecommunications company based in Bangladesh. Emerging in July 2008 from former BTTB (Bangladesh Telegraph & Telephone Board)’s submarine cable project, BSCCL presently handles Bangladesh’s lone submarine cable as a member of the SEA-ME-WE4 international submarine cable consortium that runs a total length of 20,000 km through 17 landing points in Singapore, Malaysia, Thailand, Bangladesh, India, Sri Lanka, Pakistan, United Arab Emirates, Saudi Arabia, Egypt, Tunisia, Italy, Algeria and France.

Introduction to Submarine Cable:

# What is Submarine Cable?

Submarine Cable is the cable designed to be placed underwater. Such cables must be specially protected against moisture. At shallow depths on continental shelves, submarine cables commonly are plowed in and armored to protect them against ship anchors, trawler nets, and sharks, which are attracted to the electromagnetic fields and like to gnaw on the cables and repeaters. Submarine Cable was first inaugurated in 1956 containing 4000 voice circuits, termed as TAT-1. Later TAT-8 version, containing 3500 voice circuits was come out in 1983. TAT stands for Trans Atlantic Telephone.

EARLY HISTORY (TELEGRAPH AND COAXIAL CABLES)

TRIALS:

After William Cooke and Charles Wheatstone had introduced their working telegraph in 1839, the idea of a submarine line across the Atlantic Ocean began to be thought of as a possible triumph of the future. Samuel Morse proclaimed his faith in it as early as the year 1840, and in 1842 he submerged a wire, insulated with tarred hemp and India rubber, in the water of New York Harbor, and telegraphed through it. The following autumn Wheatstone performed a similar experiment in Swansea Bay. A good insulator to cover the wire and prevent the electric current from leaking into the water was necessary for the success of a long submarine line. India rubber had been tried by Moritz von Jacobi, the Prussian electrical engineer, as far back as the early 1800s.

FIRST COMMERCIAL CABLES:

In August 1850, John Watkins Brett's Anglo-French Telegraph Company laid the first line across the English Channel. It was simply a copper wire coated with gutta-percha, without any other protection. The experiment served to keep alive the concession, and the next year, on November 13, 1851, a protected core, or true cable, was laid from a government hulk, the Blazer, which was towed across the Channel. The next year, Great Britain and Ireland were linked together. In 1852, a cable laid by the Submarine Telegraph Company linked London to Paris for the first time. In May, 1853, England was joined to the Netherlands by a cable across the North Sea, from Orford Ness to The Hague. It was laid by the Monarch, a paddle steamer which had been fitted for the work.

TRANSATLANTIC TELEGRAPH CABLE:

The first attempt at laying a transatlantic telegraph cable was promoted by Cyrus West Field, who persuaded British industrialists to fund and lay one in 1858. Subsequent attempts in 1865 and 1866 with the world's largest steamship, the SS Great Eastern, used a more advanced technology and produced the first successful transatlantic cable. The Great Eastern later went on to lay the first cable reaching to India from Aden, Yemen, in 1870.

CABLE TO INDIA, SINGAPORE, FAR EAST AND AUSTRALASIA:

An 1863 cable to Bombay provided a crucial link to Saudi Arabia. In 1870 Bombay was linked to London via submarine cable in a combined operation by four cable companies, at the behest of the British Government. In 1872 these four companies were combined to form the mammoth globespanning Eastern Telegraph Company, owned by John Pender. A spin-off from Eastern In 1872, Australia was linked by cable to Bombay via Singapore and China and in 1876 the cable linked the British Empire from London to New Zealand

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 SUBMARINE CABLE ACROSS THE PACIFIC:

This was completed in 1902–03, linking the US mainland to Hawaii in 1902 and Guam to the Philippines in 1903. Canada, Australia, New Zealand and Fiji were also linked in 1902.Decades later, the North Pacific Cable system was the first regenerative (repeatered) system to completely cross the Pacific from the US mainland to Japan. The US portion of NPC was manufactured in Portland, Oregon, from 1989–1991 at STC Submarine Systems, and later Alcatel Submarine Networks. The system was laid by Cable & Wireless Marine on the CS Cable Venture in 1991.

 MODERN HISTORY OPTICAL TELEPHONE CABLES:

In the 1980s, fiber optic cables were developed. The first transatlantic telephone cable to use optical fiber was TAT-8, which went into operation in 1988. A fiber-optic cable comprises multiple pairs of fibers. Each pair has one fiber in each direction. TAT-8 had two operational pairs and one backup pair.

Modern optical fiber repeaters use a solid-state optical amplifier, usually an Erbium-doped fiber amplifier. Each repeater contains separate equipment for each fiber. These comprise signal reforming, error measurement and controls. A solid-state laser dispatches the signal into the next length of fiber. The solid-state laser excites a short length of doped fiber that itself acts as a laser amplifier. As the light passes through the fiber, it is amplified. This system also permits wavelength-division multiplexing, which dramatically increases the capacity of the fiber.

Repeaters are powered by a constant direct current passed down the conductor near the center of the cable, so all repeaters in a cable are in series. Power feed equipment is installed at the terminal stations. Typically both ends share the current generation with one end providing a positive voltage and the other a negative voltage. A virtual earth point exists roughly half way along the cable under normal operation. The amplifiers or repeaters derive their power from the potential difference drop across them. The optic fiber used in undersea cables is chosen for its exceptional clarity, permitting runs of more than 100 kilometers between repeaters to minimize the number of amplifiers and the distortion they cause. Originally, submarine cables were simple point-to-point connections. With the development of submarine branching units (SBUs), more than one destination could be served by a single cable system. Modern cable systems now usually have their fibers arranged in a self-healing ring to increase their redundancy, with the submarine sections following different paths on the ocean floor. One driver for this development was that the capacity of cable systems had become so large that it was not possible to completely back-up a cable system with satellite capacity, so it became necessary to provide sufficient terrestrial back-up capability. Not all telecommunications organizations wish to take advantage of this capability, so modern cable systems may have dual landing points in some countries (where back-up capability is required) and only single landing points in other countries where back-up capability is either not required, the capacity to the country is small enough to be backed up by other means, or having back-up is regarded as too expensive.

A further redundant-path development over and above the self-healing rings approach is the "Mesh Network" whereby fast switching equipment is used to transfer services between network paths with little to no effect on higher-level protocols if a path becomes inoperable. As more paths become available to use between two points, the less likely it is that one or two simultaneous failures will prevent end-to-end service.

STRUCTURE OF SUBMARINE CABLE:

 The basic structure of the submarine communication cable consists of the polyethylene, Mylar tape, standard steel wires, aluminum water barriers, polycarbonate, copper aluminum tube, petroleum jelly and optical fibers. The first component used in making optical fiber is the polyethylene which is a type of plastic, containing long chain of monomer ethylene. Mylar tape is used for reflectivity and stability. A combination of standard steel wires is used in cables to make it durable. An aluminum barrier is used to protect cable from the damage inside the water. Aluminum is water resistant element. Polycarbonate is also used in submarine cables because this component is temperature resistant and provides optical functionality.  A layer of petroleum jelly is often used because it is not soluble in water. Afterwards the optical fiber is protected in the covering of aluminum barriers. Hence the cable can withstand the changes in the temperature of the water and does not dissolve at all. While making the cable it is assured that it would work well because the damage would leave us deprived of any communication.

CROSS SECTION:

                              Fig: cross section of a submarine communications cable

A cross section of a submarine communications cable:

1.Polyethylene
2. Mylar tape

3.Stranded steel wires
4.Aluminium water barrier
5. Polycarbonate
6.Copper or aluminium tube
7.Petroleum jelly

8.Optical fiber

                       

Fig: Cut away view of double-armored SL cable

 v  CATEGORY OF A SUBMARINE CABLE:

LIGHT WEIGHT CABLE:

A light weight cable is used in deep sea areas of around 1,000m to 8,500m depth.

                                    

                                      Fig: Structure of light weight optical submarine cable.

                                  

SINGLE ARMORED SUBMARINE CABLE:

An armored cable being attached a steel wire to the light weight cable, and is used in a shallower area than about 1,000m depth.

                                  Fig: Structure of single armored submarine cable

DWDM  TECHNOLOGY:

Dense Wavelength Division Multiplexing, an optical technology used to increase bandwidth over existing fiber optic backbones. DWDM works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber. To multiplex eight OC -48 signals into one fiber, carrying capacity of that fiber from 2.5 Gb/s to 20 Gb/s. single fibers have been able to transmit data at speeds up to 400Gb/s.A key advantage to DWDM is that it's protocol- and bit-rate-independent. DWDM-based networks can transmit data in IP, ATM, SONET /SDH, and Ethernet, and handle bit rates between 100 Mb/s and 2.5 Gb/s. Therefore, DWDM-based networks can carry different types of traffic at different speeds over an optical channel.The regions, called windows, lie between areas of high absorption. The earliest systems were developed to operate around 850 nm, the first window insilica-based optical fiber. A second window (S band), at 1310 nm. The four windows are shown relative to the electromagnetic spectrum in figure :

      

Fig: DWDM Functional Schematic

The system performs the following main functions:

• Generating the signal

• Combining the signals

• Transmitting the signals

• Separating the received signals

• Receiving the signals

Why DWDM?

From both technical and economic perspectives, the ability to provide potentially unlimited transmission capacity is the most obvious advantage of DWDM technology. The current investment in fiber plant can not only be preserved, but optimized by a factor of at least 32. As demands change, more capacity can be added, either by simple equipment upgrades or by increasing the number of lambdas on the fiber, without expensive upgrades. Capacity can be obtained for the cost of the equipment, and existing fiber plant investment is retained.

• Transparency

• Scalability

• Dynamic provisioning

DIFFERENCE BETWEEN TDM & DWDM:

TDM takes synchronous and asynchronous signals and multiplexes them to a single higher bit rate for transmission at a single wavelength over fiber. Source signals may have to be converted from electrical to optical, or from optical to electrical and back to optical before being multiplexed. WDM takes multiple optical signals, maps them to individual wavelengths, and multiplexes the wavelengths over a single fiber. Another fundamental difference between the two technologies is that WDM can carry multiple protocols without a common signal format, while SONET cannot. Some of the key differences between TDM and WDM are graphically illustrated in Figure :

Fig: TDM and DWDM Interfaces

SEA-ME-WE:

South East Asia–Middle East–Western Europe 4(SEA-ME-WE ) is an optical fibre submarine communications cable system that carries telecommunications between different country.

SEA-ME-WE-1:

South East Asia–Middle East–Western Europe 1(SEA-ME-WE ) is an optical fibre submarine cable

SEA-ME-WE-2:

South East Asia–Middle East–Western Europe 2(SEA-ME-WE ) is an optical fibre submarine cable which start from 1991.

SEA-ME-WE-3:

SEA-ME-WE 3 or South-East Asia - Middle East - Western Europe 3 is an optical submarine telecommunications cable linking those regions and is the longest in the world, completed in late 2000. It is operated by India's Tata Communications and 92 other investors from the telecom industry. It was commissioned in March 2000. It is 39,000 kilometres (24,000 mi) in length and uses Wavelength Division Multiplexing (WDM) technology with Synchronous Digital Hierarchy (SDH) transmission to increase capacity and enhance the quality of the signal, especially over long distances (this cable stretches from North Germany to Australia and Japan).

SEA-ME-WE-4:

South East Asia–Middle East–Western Europe 4 (SEA-ME-WE 4) is an optical fibre submarine communications cable system that carries telecommunications between Singapore, Malaysia, Thailand, Bangladesh, India, Sri Lanka, Pakistan, United Arab Emirates, Saudi Arabia, Sudan, Egypt, Italy, Tunisia, Algeria and France. It is intended to be a complement to, rather than a replacement for, the SEA-WE-ME 3 cable. The cable is approximately 18,800 kilometres long, and provides the primary Internet backbone between South East Asia, the Indian subcontinent, the Middle East and Europe.

LANDING STATION:

The country may be fibre-optically connected with India by the first week of November, as a terrestrial cable linking the two nations is set to be operational within four weeks. The 25-km link connects Darshana of Bangladesh with Krishno Nagar of India to act as an alternative backbone to the submarine cable in case of emergency.

   

 The length of  the  Branch point from the Bangladesh  point are 1015.696 km using 14 repeaters and 1 equilizer.

1∂=10 Gbps

64∂=640 Gbps

MAJOR EQUIPMENTOF LANDING STATION:

1. 1.      Power feeding equipment(PFE)
2. 2.      Submarine line terminating equipment(SLTE)
3. 3.      SDH interconnection equipment(SIE)
4. 4.      System Surveillance Equipment (SSE)

                                              Fig: Operation procedure

IIG: International Internet Gateway

IGW: International Gateway

ICX: Inter Connection Exchange

BBU: Broad Band User

ISP:

DISCUSSION:

Optical networking, unlike SONET/SDH, does not rely on electrical data processing. As such, its

development is more closely tied to optics than to electronics. In its early form, as described previously, WDM was capable of carrying signals over two widely spaced wavelengths, and for a relatively short distance. To move beyond this initial state, WDM needed both improvements in existing technologies and invention of new technologies. Improvements in optical filters and narrowband lasers enabled DWDM to combine more than two signal wavelengths on a fiber. The invention of the flat-gain optical amplifier, coupled in line with the transmitting fiber to boost the optical signal, dramatically increased the viability of DWDM systems by greatly extending the transmission distance. Other technologies that have been important in the development of DWDM include improved optical fiber with lower loss and better optical transmission characteristics, EDFAs, and devices such as fiber Bragg gratings used in optical add/drop multiplexers             

Practical Experience of visiting a landing station is of high importance. The sub gate way has been maintaining the SEA-ME-WE-4 consortium for the last few years, providing the country with connectivity with rest of the world. It is regrettable that we could not connect to submarine cable when it was supposed to be given at free of cost. But there still remains anticipation that by the proper use of the submarine cable and internet connectivity, the information technology of our country may take quick steps soon. Being a student of Information Technology, the tour has highly been informative to us.