Fiber-Optic Sensors

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About This Technology

October 2006

Fiber-optic sensors are a powerful class of sensors, bringing to measurement systems many of the advantages that optical-fiber technology has brought to communications systems. Three main characteristics differentiate fiber-optic sensors from other types of sensors: The very high bandwidth of optical fibers allows them to convey a large amount of measurand information through a single fiber; because optical fiber is a dielectric, it is not subject to interference from electromagnetic waves that might be present in the sensing environment; and fiber-optic sensors can function under adverse conditions of temperature and pressure, and toxic or corrosive atmospheres that can erode metals at a rapid rate have little effect on optical fibers. In addition, fiber-optic sensors are intrinsically safe in explosive environments (no sparks), lightweight, compact, robust, and potentially inexpensive. They are therefore useful as sensing devices for a wide range of physical and chemical phenomena that include temperature, pressure, acoustic field, position, rotation, electrical current, liquid level, biochemical composition, and chemical concentration. Indeed, fiber-optic sensors can perform the functions of virtually any conventional sensor—often faster and with greater sensitivity—and they can also perform measurement tasks that would be impracticable with conventional sensors. For instance, they can be embedded in critical structures, such as airplanes and bridges, reporting continuously on structural integrity, and possibly averting a catastrophic failure.

The telecommunications industry was primarily responsible for the development of fiber-optic sensor technology in 1980s. However, in spite of their special capabilities, fiber-optic sensors did not rapidly progress to industrial applications. The challenges of performance, cost, modularity, and standardization all limit industrial penetration. Indeed, for an indefinite period, electronic sensors—which are well supported by electronic signal-handling methods and hold established positions in control systems—will coexist with fiber-optic sensors. But electronic signal-handling methods can serve fiber-optic sensors because optical signals readily convert into electronic form. And in the longer term, all-optical signal-handling methods will become available, complementing and extending the capabilities of fiber-optic sensors.

The numerous advantages of fiber-optic sensors will ensure that they continue to attract research funding for their further development. The maturation of fiber-optic technology will, over time, expand the applications of fiber-optic sensors as the cost of components such as coherent laser sources and single-mode couplers declines and component performance improves. And with the drive toward automation by manufacturing facilities all over the world, the many inherent advantages of fiber-optic sensors portend a major role for them in the future.