Resource Assessment & Conservation Engineering (RACE) Division

Groundfish Assessment Program

Fiber-Optic Habitat-Mapping System Tested by FISHPAC

RACE scientists working in conjunction with the FISHPAC project are developing a fiber-optic interface (FOI) for mapping and groundtruthing seabed habitat in Alaska. The FOI is intended to support both digital sidescan sonar and a towed high-resolution video system to depths of 500 m. A fundamental requirement of this system is rapid switching between the sonar and video systems, according to mission requirements, based on a common subsea connection.

The FOI consists of 1) a high-speed cantilevered tow winch that permits rapid exchange of the spooled drum and slip ring as a unit, 2) 1,200 m of armored multimode fiber tow cable, 3) a combined electrical-optical rotary joint, 4) a stainless steel mechanical cable termination with electrical and mechanical connections, plus 5) subsea and topside electronics to provide power to lights, cameras and the sonar, and to manage multiplexed data from multiple serial ports, analog video, and uncompressed 400 Mbps ("Firewire") video (Fig. 1 below).

Figure 1.  Subsea electronics that support multiplexed data communications between submerged instruments and topside computers.  Photo by Karna McKinney.

A prototype system was tested during the week 31 January – 4 February 2005. Bench testing in Seattle confirmed general capabilities of the system, while sea trials in Puget Sound aboard the 57-m U.S. Navy vessel Battle Point evaluated performance with a Klein 5410 sidescan sonar and a revamped towed automatically compensating observation system (TACOS) video system (Fig. 2 below).

Figure 2.  Sidescan sonar being prepared for launch during sea trials in Puget Sound. Photo by Doug Swain.

Technical support was provided by the Naval Undersea Warfare Center (Keyport, WA), as well as DWS International Inc. (Corpus Christi, TX), L-3 Klein Associates (Salem, NH), MacArtney Underwater Technology A/S (Esbjerg, Denmark), and the University of New Hampshire (Durham, NH). Additional Puget Sound sea trials will occur later this year. Operational deployment in the eastern Bering Sea is planned for summer 2006.

By Bob McConnaughey

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AFSC Quarterly Research Reports Jan-Mar 2005