Demonstration testd of LBVDS instrumented tow cable in waters south of New England-initial results

The Lightweight Broadband Variable Depth Sonar (LBVDS) Instrumented Tow Cable is capable of measuring the temperature vs. depth profile on a near-continuous basis with virtually no impact to the mechanical properties of the steel-armored tow cable. The design is a modification of a conventional steel-armored tow cable involving the replacement of several of the outer steel armor wires with stainless steel tubes containing optical fibers. The stainless steel tubes maintain the same diameter as the original armor wires, so the overall cable diameter is unchanged. The resulting measurement capability will have significant implications for environmental adaptation of U.S. Navy sonar systems. Temperature is obtained through the use of the Raman scattering effect in the optical fibers. The approach supports temperature measurement with a depth resolution of ½ meter. In performance tests under controlled conditions at Seneca Lake, the standard deviation against XBTs was found to be approximately 0.3 degrees C for repeated runs. Runs were performed with both powered (up to 1.5 W/ft dissipation) and unpowered electromechanical tow cables. Further improvements in temporal and spatial averaging have been realized in the next generation system, which was used to sample the dynamics of the shelf-slope front south of New England. Instrumented tow cable technology has virtually no impact on the cable mechanical properties. It is easily adaptable to any steel-armored tow cable for any applications requiring frequent environmental temperature measurements, and its capabilities to measure ocean temperature dynamics were demonstrated in these initial results