Primary Backbone Cables
The OOI Regional Cabled Array (RCA), through a partnership with L3 MariPro, builds on telecom industry sub-sea cable to provide power (10 kV DC, up to 8 A) and communications (10 Gb/s) via fiber-optics and copper between the Primary Nodes and the Shore Station in Pacific City, Oregon. The backbone cable was installed Summer 2011 using the commercial cable laying ship, the TE SubCom Dependable and was designed for at least a 25 year life expectancy.
Approximately 900 km of primary backbone cable, installed as two main sections, was installed from the Shore Station to the seven Primary Node locations spanning the Juan de Fuca Plate. One branch extends ~480 km due west to Axial Seamount, the largest volcano on the Juan de Fuca Ridge. The second branch extends 208 km southward along the base of the Cascadia Subduction Zone (2900 m) and then turns east extending 147 km to 80 m water depth offshore Newport, Oregon. The backbone cables, at water depths of ~1500 m, are armored and buried to ~1-2 m. The system is designed for a 25-year life.
RCA Extension Cables provide power and communication links between the Primary and Secondary Infrastructure (junction boxes, instrumented moorings, and sensors). Over 33,000 m of extension cables are installed at lengths up to ~ 5 km and from water depths of 80 m to 2900 m. They were installed in 2013 and 2014 using the Canadian Scientific Submersible Facility remotely operated vehicle ROPOS with the ROCLS system (remotely operated cable laying system) attached to its underbelly. All cables have functioned perfectly since their installation.
The cables were installed in a variety of environments, including the extremely rugged summit of Axial Seamount. There are numerous cable types used depending on communication (e.g. RS-232, RS-422/485, Ethernet 10/100 BASE-T) and power requirements, respectively. Cable lengths connected to instruments are typically 10 m to 50 m in length, but may extend to over 1 km to connect short-period seismometers to junction boxes, for examples.
An important design decision for the RCA was the use of wet-mate connectors on cables and junction boxes to optimize efficiency in operations. Wet-mate connectors allow coupling and uncoupling of cables from platforms and instruments with an ROV without having to bring infrastructure to the entire junction box or mooring to the surface, for example. In general, there are three major types of connectors: Wet-Mate Electrical Connectors, Wet-Mate Hybrid Connectors, and Dry-Mate Electrical Connectors. Typically Dry-Mate connectors are used to connect instruments on platforms such as the winched shallow profiler science pod, which is recovered every year. In 2018, a new type of Teledyne ODI wet-mate connector adaptation was utilized called a Gross Alignment Funnel (GAF) that help guides connectors into their receptacles.
The UW RCA team works with researchers interested in installing platforms/instruments onto the cabled observatory, providing guidance on the optimal cable type and connector to use for connection of their infrastructure onto the array.