The evolution of optical fiber cable design for sensor applications

Abstract

Since its invention in the 1970s, optical fiber has provided a technology-based vehicle to improve the performance of a variety of applications that were traditionally served by older copper conductor based systems. Optical fiber based systems have enabled improvements in capabilities and functionality that are simply not possible with copperonly systems. Typically, optical fiber systems enable higher rates of data transfer over longer transmission distances. Telecommunications applications have demonstrated this benefit through improved capability for voice, data and video transmission. Field deployment of optical fiber is executed through the utilization of a protective cabling structure that allows the optical fiber to be safely installed and be protected over its service life. The design and construction of each cable is based upon the expected mechanical and environmental conditions of the operating environment. Performance requirements, published in detailed specifications or industry standards, must also be considered to provide a system with an appropriate service life for each application. Optical fiber applications have now expanded beyond telecommunications. Sensor applications utilizing optical fiber to measure temperature, pressure, acoustics and seismic parameters are being deployed and evaluated today. Applications in Oil and Gas Exploration, Geothermal and Fire Detection Monitoring are being supported by optical fiber-based systems. The sensing environment typically exposes the optical fibers to much more extreme environments that are not prevalent in telecommunications. This includes high temperatures, high pressures and harsh chemical exposure that must be addressed in the cable design containing the fibers in order to extend the useful life of the fibers as much as practical. While optical cable for sensing applications require some specialization, there are basic cable design tenants that still apply to construct a cable that meets or exceeds the application environment. In many cases, design concepts proven in older copper-based cables may be adapted to incorporate one or more optical fibers. Nevertheless, more extreme environments require the use of nontraditional materials and alternative design concepts not utilized in typical telecommunications applications. Some sensor applications, due to their specialized nature, may drive one or more design aspects in a manner that contradicts established telecommunications cable design practices. The focus of this paper is to compare and contrast the cable construction differences between sensing applications and traditional telecommunications applications, review the significant design considerations for the associated application and outline several current design challenges necessary to enable reliable cable deployments.