A Fiber Optic Dynamic Riser Cable System for Deep Water Application
Authors: Ma C.S. , Stix R.K. , Rue R.J. , Gleason R.F. 
Published: October 2008

This paper presents a newly developed riser cable system for optical fiber communications to floating platforms. The system uses the current technology of undersea optical fiber cable and augments it to survive the severe dynamic environment of a floating platform. The whole system is designed to last 25 years, including the effects of a IOO-year storm. The riser cable is designed to avoid buckling and to have high stability under rough wave and current conditions. The termination and joint for the riser cable are designed to maintain strength, optical, and electrical continuity. The termination may be attached to the platform above or below the water line.

Introduction

Advances in remote sensing, offshore structure, and deep drilling technologies have allowed platforms to be installed increasingly far away from the shore. Accordingly, the demand for deeper riser cables, including communication cables, has increased. Based on long experience in optical undersea cable development, a new riser cable has been developed to meet the lOOO-meter depth requirement for the floating platforms of the Campos Basin Project with its severe environmental conditions.

The riser system includes the dynamic riser cable (DRC), the dynamic rig termination which connects the riser cable to the platform and to a static platform cable, and the hybrid Universal Quick Joint (UQJ) which attaches the riser cable to the submarine cable on the sea bed. Figure 1 shows a schematic diagram of this riser system and its connection to the adjacent cables.(available in full paper)

The static bottom cable, the primary transmission cable between platforms, is standard repeaterless cable with a single outer layer of high strength steel armor wires. The protected platform cable is a special applications cable which incl.udes a protective layer of steel tape and an outer polyethylene Jacket. The dynamic rig termination is designed to be waterproof, hence it can be installed under water to meet specific project requirements. The tension and any torsion that may exist in the riser is held at the rig termination, isolating the platform cable from these loads. The total length of riser cable used for a floating platform is about twice the length of its catenary. Thus about half of the riser cable is laid on the sea bottom. This isolates the hybrid UQJ between the riser and the bottom cables from the dynamic riser cable loads.

Details of the riser cable and termination designs, their properties, environmental forces, and the qualification program are discussed in the following sections.

Dynamic Riser Cable (DRC)

Riser Cable Design.

The dynamic riser cable can be thought of as consisting of three parts. The first is the central core, referred to as the unit fiber structure (UFS), which accommodates the optical fibers. The second part includes the strength members and insulation surrounding the core. The third part consists of the outer armor layers. The UFS is the same as that developed for Tyco Submarine Systems Ltd. (TSSL) high fiber count SL cable [1].