John S. Laudo

Distributed fiber optic acoustic sensor for leak detection

Leaks in dielectric fluid-filled, high-voltage distribution lines can cause significant problems for the electric power industry. Often, these lines run over long distance and are difficult to access. Operators may know that a leak exists because additional fluid is required to maintain pipe pressure; however, locating the leak is often a significant challenge. A system that could monitor and locate leaks within the electrical distribution pipe lines would be highly desirable. We present a distributed fiber optic acoustic sensor technology that could be used to measure and locate leaks within fluid-filled, high-voltage distribution lines. In this application, the optical fiber sensor is placed inside the fluid-filled pipe and can potentially locate leaks to within several meters. The fiber optic acoustic sensor is designed such that it can listen to the sound produced by the fluid as it escapes from the pipe into the surrounding soil. The fluid inside the pipe is typically maintained at a pressure of 200 psi and escapes at high velocity when a leak occurs. The distributed fiber optic sensing system being developed is based upon the Sagnac interferometer and is unusual in that range information is not obtained by the more common method of optical time domain reflectometry or optical frequency domain reflectometry, but by essentially a CW technique which works in the frequency domain. It is also unusual in that the signal processing technique actually looks for the absence of a signal.

Applicability of a novel distributed fiber optic acoustic sensor for leak detection

We present a distributed fiber optic acoustic sensor technology that could be used to measure and locate leaks within either fluid- or gas-filled distribution lines. For these applications, the optical fiber sensor would be placed inside the pipe and could potentially locate leaks to within several meters by listening to the acoustic emission produced by the fluid or gas as it escapes from the pipe.

Liquid-filled underwater camera lens system

A novel underwater camera lens design is presented which replaces all interstitial air spaces with a low refractive index liquid to allow pressure compensation of the system in a thinner, safer diving package. The optical design presented overcomes the loss of refractive power by the liquid in a high performance, all spherical, f/1.2 lens, which operates over a 20-degree field of view. A design modulation transfer function of 0.85 is obtained at a typical CCD frequency of 50 lp/mm.