Due to the advantages of fiber optical transmission over electrical transmission, optical fibers have been researched extensively. Among those researches, one of the fields of optical fibers is designing a sensing system based on optical fibers and optical sensors. And as optical fibers are being deployed in an increasing number with lowering cost, fiber optic sensors (FOSs) replaced ordinary ones and keep growing. It is also expected that optical sensors will have a broad prospect. In this article, the fundamentals of fiber optic sensors will be reviewed, along with the basic introduction, types, applications and prospect.
Fiber optic sensor is a sensor that uses optical fiber either as the sensing element or as a means of relaying signals from a remote sensor to the electronics that process the signals. It consists of optical source (LASER, laser diode, LED, etc), optical fiber as transmission channel, sensing element, optical detector and end processed devices (oscilloscope, optical spectrum analyzer, etc). Compared to conventional electronics sensors, it has numerous advantages such as compact size, light weight, immunity to electromagnetic interface, high performance and larger bandwidth, etc.
Fiber optic sensors can be classified by different standards including the sensing location, the operating principal and applications. By the first standard, they can be classified into intrinsic or extrinsic sensors. By the second standard, they can be divided into intensity, phase, frequency or polarization sensors. And by the last standard, they can be classified into physical, chemical, bio-chemical sensors. Here is a brief introduction of intrinsic and extrinsic sensors.
Intrinsic fiber optic sensor: it has a sensing region within the fiber and light never goes out of fiber.
Extrinsic fiber optic sensor: the light in it has to leave the fiber and reach the sensing region outside and then comes back to the fiber.
- Mechanical measurements: force, pressure, strain/stress, displacement, temperature, acceleration, vibration, acoustics
- Electrical and magnetic measurements
- Chemical and biological sensing
Fiber optic sensor market is potential in the future. It is 1.99billion in 2014 and expected to reach 3.15 billion by 2019, at a compound annual growth rate (CAGR) of 9.6%. According to the picture, the market is growing at an increasing rate, up from 5.2% to 10.4%. It will give rise to greater implementation of optical sensors in regular life for their transparent advantages over electronic sensors and various applications in physical, chemical and bio-chemical fields. China has dominated the fiber optic sensor market and plans to expand its market share at higher speed.
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