Introduction

Optical fiber-based sensor instrumentation has been used extensively for the measurement of physical observables including strain, temperature, and chemical changes in smart materials and smart structures, and has been integrated with MEMS devices to provide multi-measurement capability along the length of a fiber link or network. This plenary paper briefly outlines recent developments in such optical fiber sensor instrumentation. Fiber optic sensors are small in size, immune to electromagnetic interference, and can be easily integrated with existing optical fiber hardware and components that have been developed primarily for use in the larger telecommunications market. Such sensors can be easily multiplexed, resulting in networks that can be used for the health monitoring of large structures, or the real-time monitoring of structural parameters required for structural analysis and control. Fiber-optic sensors are being used in a wide variety of applications. Sagnac interferometers, which can determine movement by measuring the shift in interference fringes from two counter-propagating coherent beams in a ring, support fiber gyros on aircraft, missiles, rockets, and robots. Michelson interferometers, in which interference fringes indicate the length relationship between two legs of the interferometer, support strain, and acoustics measurements for civil structures and underwater applications. Another type of fiber sensor, fiber grating sensors, is emerging as a potential low-cost solution to a wide variety of point-sensor measurements such as axial strain and temperature, transverse strain, shear strain, moisture, pressure, acoustics, vibration, and chemical content. Applications areas for these sensors include aerospace and structural monitoring. Over the past 20 years, two major product revolutions have taken place due to the growth of the optoelectronics and fiber-optic communications industries. The optoelectronics industry has brought about such products as compact disc players, laser printers, bar code scanners, and laser pointers. The fiber-optic communication industry has literally revolutionized the telecommunication industry by providing higher performance, more reliable telecommunication links with ever-decreasing bandwidth costs. This revolution is bringing about the benefits of high volume production to component users and a true information superhighway built of glass. In parallel with these developments, fiber-optic sensor technology has been a major user of technology associated with the optoelectronic and fiberoptic communication industry.

Fabry-Perot Interferometry Temperature Measurement

An example of a specialized application for optical fibers is the measurement of high temperatures using the Fabry-Perot interferometry method. This technology utilizes a small, thin disk of sapphire as a temperature sensor. The thickness of this disk, as well as the speed of light through the sapphire, are both temperature-dependent, which means a photon of light shot at the face of the disk will reflect off the back face of the disk and return to the source at different times depending on the temperature of the disk. In a Fabry-Perot interferometer instrument, the “optical thickness” of the sapphire disk is measured by sending a continuous beam of white light to the disk and receiving the reflected light from the disk through a single optical fiber, the optical interference resulting from the incident and reflected light beams representing the disk’s temperature. This novel method of temperature measurement shows promise for certain challenging industrial process applications such as high-temperature measurement inside slagging coal gasifiers used to efficiently extract energy and chemical feedstocks from coal:

Instrumentation Course

FUTURE SCOPE

New fiber initiatives happen all the time. According to Forbes, many cities around the world are starting to consider using fiber optic cables for their communication networks. They reported that San Francisco has pledged to connect a city-wide fiber-optic network, making it the first major city in America to commit to such a project. Meanwhile, another network provider has planned to run 8,000 miles of submarine underwater fiber optic cable from Los Angeles to Hong Kong, in order to support increased demand for Facebook and Google. The investment may be considerable, but the returns will be as well, with an astounding capacity of 144 TB.

Additionally, the rollout and expansion of 5G wireless network is made possible by fiber optics. Telecom leaders are relying on millions of miles of new fiber-optic cables which allow 5G devices across the globe to connect with one another. In the future, it is possible to see new fiber initiatives in more diverse and efficient applications.

JOB OPPURTUNITIES

The job of a fiber optic engineer is centered on the installation of broadband telecommunication cables, which include fiber optic cables. These cables transmit information by converting messages into light pulses which travel through these cables rapidly over long distances. These cables have an edge over steel cables since the transfer of information on this medium is much quicker. The job of the fiber optic engineer is to install and test these cables, perform maintenance checks on them, and take care of any malfunctioning that may happen.

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Author: Vishnu K Nair
Department : Instrumentation
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