Submarine Fiber-Optic and DC Power Solution for Ultralong Tieback
Authors: Fullenbaum Marc , Hazell Neville , Waterworth Gary , Doyle Laurie 
Published: October 2008

The submarine telecommunications industry has been successfully transmitting data over transoceanic distances on optical fibers for nearly twenty years, using direct current (DC) electrical power to high reliability submerged repeaters. The first regional scale science observatory, which will offer 1Gbit Ethernet data and 10 kW DC power transport over an 800 km long network, is under construction and will be in service in 2007-2008.

The technology selected for this project has demonstrated power and data transport to subsea control systems 600 km away from shore. It offers flexible architectures that enable expandable, high reliability networks and intrinsic compatibility with e-Field solutions.

This paper will describe several offshore control applications, system architecture, installation methods as well as review the technology status.

Introduction

The challenges of future offshore fields include operation at greater depths, further offshore and in many environmentally difficult areas, such as the hazardous Arctic margin. This results in the need for Ultra-long step-outs. Additionally, the drive to higher extraction rates requires e- Field solutions, with commensurate high data demands.

The established subsea solutions for the international telecommunication systems that provide the backbone for the world wide web are characterized by: high capacity (100's of Gbit/s) optical fiber transmission, DC power transmission (10's of kW), and high quality, highly redundant configurations for fault free subsea use over 25 years. Over 500.000 km of such subsea solution have been laid over the past 15 years, making it the core of the global fiber grid. These solutions rely on repeatered systems whereby the optical signals are amplified solely in the optical domain. Figure 1 depicts the typical hardware in a repeatered system.

Figure 1: Key Components of Repeatered System (available in full paper)

For a subsea control system requiring Ethernet and DC power access, the aggregated data necessary to the control systems is typically in a range of 100-1000 Mbit/s back to shore and power levels of 10 kW for subsea valve operation, control systems and e-Field solutions.

The simple addition of a subsea node to the proven subsea telecom equipment readily provides the complete solution. It is also to be noted that this telecom cable may also be installed independently from any umbilical solution. Moreover this novel solution can provide interfaces for easy integration with existing production, control and monitoring equipment.

The vital control systems that maybe managed over these new cables can be protected in a 1+1 configuration (duplicated systems) in order to support the high levels of system availability required to support continuous operations. The proven technology from the telecom sector associated with a fault tolerant duplicated systems scheme enable a 99.99 % availability meeting the demanding requirements for communications to a control system.

Ultra long tie backs/step outs

A) Solution overview

The submarine telecom equipment technology may be used to connect subsea control systems, either by tiebacks to a platform or with a step-out from land direct to a field. A traditional subsea optical fiber cable is used, with multiple optical fibers and a Direct Current conductor at 10 kV.