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New Tools for Multilayered Undersea Telecommunication Networks
Dual-Conductor Cable and a Four-Cable Branching Unit Meet Evolving Needs for Transoceanic Undersea Cable Networks

By Dr. Maurice E. Kordahi
Managing Director
Wet Plant Development Tyco Electronics Subsea Communications
Morristown, New Jersey

Over the last 30 years, worldwide communication needs have exploded as consumers across the globe accelerate the sharing of real-time data in the form of Internet searches, voice and video. Business ventures today are built on the existence of a worldwide communication network capable of expanding quickly to accommodate their immediate needs.

Different market segments, such as telecommunications, oil and gas, and scientific research, require independent power and fiber connectivity that can evolve to meet their specific conditions. These requirements are leading to the design of a new type of undersea network with new undersea elements.

Multilayered Network Advantages
In the past, undersea cable networks focused on data transmission between land masses. As the need for better communications and data transfer evolves, however, networks are being envisioned that can go beyond single-purpose fiber and power management, incorporating layers of various individual networks supported by a single infrastructure. A cable that once transmitted only telecommunications data between continents could also relay data from various oil and gas platforms or from a scientific research institute's underwater observatory.
The DCC features two separate conductors, one surrounding the other.

These layered networks all share the same fundamental infrastructure of cable, amplifiers, joints and branching units. However, transmission media (i.e., optical fibers) and power paths (i.e., power conductors) must be kept independent.

The advantage of such a layered architecture is that it provides the ability to use a common infrastructure backbone to provide an economical solution not only for long-haul telecommunications connectivity between landmasses, but also for smaller applications that need to transmit low-rate local data at very long distances.

New Building Blocks
To fulfill independent power and fiber connectivity in a layered network, several undersea technological building blocks are necessary. Tyco Electronics Subsea Communications (TE SubCom) has developed two new products to meet these needs: a dual-conductor cable (DCC) and a four-cable branching unit (BU) capable of handling a third power path.

The DCC features the classic main conductor in the center with the second conductor concentric around it and polyethylene insulation between them. The whole package is isolated from sea ground with a second layer of polyethylene. This cable structure is compatible with all available cable armoring configurations and deployment techniques to ensure it can be used anywhere a traditional single conductor cable may be used.

The DCC is based on current undersea cable designs, allowing users to utilize existing tooling and procedures in manufacturing and repairing it, and cable ships require only small additional tooling to allow them to carry out repairs on these newer cables without having to invest in a dedicated suite of equipment.
Four-cable BU with two functionally independent cables.

This product is joined to itself and to amplifiers through special joints capable of connecting the two conductors while maintaining power isolation between the conductors and sea ground. The joints also provide mechanical strength termination and fiber connectivity. Based on existing products, they are similarly highly reliable and compatible with existing installation and maintenance capabilities.

The second essential element that TE SubCom has designed for layered networks is the four-cable BU, which is capable of handling three separate power paths.

Dynamic interconnection between the three cables and from the cables to sea ground is supported within the BU through a remotely controlled power switched network.

This architecture provides the inherent ability to provide power from independent sources, supply disparate power levels on the conductors, distribute power to unrelated resources and power branches from different sources, allowing the development of multilayered cable networks.

Planned Multilayered Networks
Several layered networks are already being planned that would utilize such technology, including a project in which a system connecting population centers on either side of the ocean would also collect data from an oil and gas field through optical add-drop multiplexer (OADM) BUs, as well as from a science node connected to a four-cable BU.

TE SubCom's DCC and the four-cable BU provide the ability to develop customized solutions for various users utilizing the same undersea infrastructure for distinct data transmission layers. The flexibility of these networks can be further enhanced when existing and evolving OADM capabilities are considered.

Naturally, the overall cost of layered networks is a fraction of that of several single-purpose ones. Many users would not be able to install their own infrastructure to capture and transmit ocean bottom real-time data without the ability to create such multipurpose networks.

The building blocks to support these multilayered networks are available today, ready to meet the evolving needs of the undersea telecommunications, oil and gas and scientific research markets.

Dr. Maurice E. Kordahi has more than 25 years of undersea experience. He is presently the managing director of the wet plant development organization at Tyco Electronics Subsea Communications and is responsible for the design of several underwater product lines, including fiber optic amplifiers, couplings and joints, and their introduction to manufacturing and field deployment.

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