Distributed optical fiber sensors can be used for the monitoring of pipelines, optical communication links, and in the trespassing alarm on the restricted area. The earlier detection methods were based on the intensity modulated sensors. They provide the sensing based on the loss of optical intensity (as a result of the breakage of pipe lines, tapping of communication links) from the fiber or coupled to the fiber. Thus the detection is possible only after the breakage of pipeline, tapping of data link etc. So, there is the need of a sensing scheme which can sense any phase sensitive events such as vibration, localized temperature etc, prior to the breakage.
Fiber optic interferometers exhibit a high sensitivity to vibrations, strain and other disturbances which act upon the sensing fibers. Their high sensitivity can be accounted for the fact that light is used to perform the interferometry. The wavelength of light typically used in these applications is in the order of a millionth of a meter (micrometers). Any sub- wavelength path length mismatch between the two interfering arms will lead to a significant phase difference. Sub-wavelength changes in path lengths can be readily caused by physical perturbations on the optical fiber arms, such as vibration, strain or temperature.
The objective is to design a fiber optic interferometric system, to detect, classify and locate the phase sensitive events along pipeline and communication links, and the security borders or restricted areas, with sufficient accuracy and early warning to enable corrective action to be put in place to prevent the damage and cost occurring.

• Author: Bibi Mohanan
• Pages: 82
• Binding: Paperback
• Size: 8.5x11
• Publishing Date: Jan. 12, 2016
• Category: Engineering
• Language: English