1、 1 中文 9393 字 Overview of Fiber Optic Sensors Abstract: With the development of optical sensor technology, fiber optic sensor has the advantages of resistance to electromagnetic interference, corrosion, resistance, excellent insulation, wide measuring range, easy for multiplexing, solving
2、 problems that other sensors can't solve, etc, these sensors as one of the faster-developing technology are widely applied in the field of civil engineering, aerospace, electric power, medical treatment, shipbuilding industry, and so on. In this paper, we study the basic knowledge on optical sen
3、sor technology. Keywords: fiber optic； fiber Bragg grating； optical fiber sensor 1. Introduction Optical fiber sensor is developed at the end of 70s as a new type of sensor, it has not affected by electromagnetic field effect, in essence safety explosion-proof, small size, corrosion resistance, the
4、advantages of high sensitivity. Used in traditional sensor is difficult to set foot in the extreme environment, so in the military, aviation, biological medicine, building construction field is popular. So to optical fiber sensor research has very important practical significance. Sensing technology
5、 is popular in recent years, the application of the technology in the sensitive, accurate sensor, strong adaptability, cabinet and wisdom of the direction of development. In this process, optical fiber sensors the sensor to the new members of the family is extremely popular. Optical fiber has many e
6、xcellent properties, such as: the electromagnetic interference and atomic radiation performance, diameter is fine, soft and light weight of mechanical properties, insulation, without induction electrical properties, water resistant, high temperature resistant and corrosion resistance of the chemical
7、 properties, it can not reach people places (such as high), or harmful to the person of the area (such as nuclear area), plays the role of the refreshing, and still can transcend boundaries, receiving of physiological the senses of not feeling outside information. Optical fiber sensor is a new techn
8、ology in recent years, can be used to measure physical quantities, such as sound field, electric field, pressure, temperature, angular velocity, acceleration, etc, but also can complete the existing measuring technology difficult to complete measuring task. In the narrow space, in strong electromagn
9、etic interference and high voltage environment, optical fiber sensors shows the unique 2 charm. Therefore, the optical fiber sensing technology application research has the very good prospects. Optical fiber sensor light sensitive information carrier, as the optical fibre as sensitive informa
10、tion transmission medium. Therefore, it also has the characteristics of optical fiber and optical measurement. (1) the electric insulation performance is good. (2) anti-electromagnetism interference ability. (3) the non-invasive. (4) the high sensitivity. (5) to be easy to implement the measured sig
11、nal remote monitoring 2. Basic knowledge of transducers A transducer is a device which converts the quantity being measured into an optical, mechanical, or-more commonly-electrical signal. The energy-conversion process that takes place is referred to as transduction. Transducers are classified accor
12、ding to the transduction principle involved and the form of the measured. 2.1Transducer Elements Although there are exception, most transducers consist of a sensing element and a conversion or control element. For example, diaphragms, bellows strain tubes and rings, bourdon tubes, and cantilev
13、ers are sensing elements which respond to changes in pressure or force and convert these physical quantities into a displacement. This displacement may then be used to change an electrical parameter such as voltage, resistance, capacitance, or inductance. Such combination of mechanical and electrica
14、l elements form electromechanical transducing devices or transducers. Similar combination can be made for other energy input such as thermal. Magnetic and chemical, giving thermoelectric, electromaanetic, and electrochemical transducers respectively. 2.2Transducer Sensitivity The relationship betwee
15、n the measured and the transducer output signal is usually obtained by calibration tests and is referred to as the transducer sensitivity K1= output-signal increment / measured increment . In practice, the transducer sensitivity is usually known, and, by measuring the output signal, the input quanti
16、ty is determined from input output-signal increment / K1. 3 2.3Characteristics of an ideal transducer 1) high fidelity-the transducer output waveform shape be a faithful reproduction of the measured； there should be minimum distortion. 2) There should be minimum interference with the qu
17、antity being measured； the presence of the transducer should not alter the measured in any way. 3) Size. The transducer must be capable of being placed exactly where it is needed. 4) There should be a linear relationship between the measured and the transducer signal. 5) The transducer should have m
18、inimum sensitivity to external effects. 6) The natural frequency of the transducer should be well separated from the frequency and harmonics of the measurand. 2.4 Photoconductive Cells The photoconductive cell, uses a light-sensitive semiconductor material. The resistance between the metal ele
19、ctrodes decrease as the intensity of the light striking the semiconductor increases. Common semiconductor materials used for photo-conductive cells are cadmium sulphide, lead sulphide, and copper-doped germanium. The useful range of frequencies is determined by material used. Cadmium sulphide is mai
20、nly suitable for visible light, whereas lead sulphide has its peak response in the infra-red region and therefore most suitable for flame-failure detection and temperature measurement. 3. Optical fiber system An optical fiber is a flexible, transparent fiber made of glass (silica) or plastic, slight
21、ly thicker than a human hair. It can function as a waveguide, or light pipe 1, to transmit light between the two ends of the fiber.2 The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. Optical fibers are widely used in fi
22、ber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication. Fibers are used instead of metal wires because signals travel along them with less loss and are also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles so that they may be used to carry images, thus allowing viewing in confined spaces. Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers. Optical fibers typically include a transparent core
