外文翻譯--光纖傳感器概述

1、<p><b>　　中文9393字</b></p><p>　　Overview of Fiber Optic Sensors</p><p>　　Abstract: With the development of optical sensor technology, fiber optic sensor has the advantages of resi

2、stance to electromagnetic interference, corrosion, resistance, excellent insulation, wide measuring range, easy for multiplexing, solving problems that other sensors can't solve, etc, these sensors as one of the fast

3、er-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 s</p><p>　　Keywords: fiber opt

4、ic; fiber Bragg grating; optical fiber sensor</p><p>　　1. Introduction</p><p>　　Optical fiber sensor is developed at the end of 70s as a new type of sensor, it has not affected by electromagneti

5、c field effect, in essence safety explosion-proof, small size, corrosion resistance, the advantages of high sensitivity. Used in traditional sensor is difficult to set foot in the extreme environment, so in the military,

6、 aviation, biological medicine, building construction field is popular. So to optical fiber sensor research has very important practical significance. Sensing technol</p><p>　　(1) the electric insulation per

7、formance is good.</p><p>　　(2) anti-electromagnetism interference ability.</p><p>　　(3) the non-invasive.</p><p>　　(4) the high sensitivity.</p><p>　　(5) to be easy to

8、implement the measured signal remote monitoring</p><p>　　2. Basic knowledge of transducers</p><p>　　A transducer is a device which converts the quantity being measured into an optical, mechanica

9、l, or-more commonly-electrical signal. The energy-conversion process that takes place is referred to as transduction. Transducers are classified according to the transduction principle involved and the form of the measur

10、ed. </p><p>　　2.1Transducer Elements</p><p>　　Although there are exception, most transducers consist of a sensing element and a conversion or control element. For example, diaphragms, bellows st

11、rain tubes and rings, bourdon tubes, and cantilevers 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 cha

12、nge an electrical parameter such as voltage, resistance, capacitance, or inductance. Such combination of mechanical and electrical e</p><p>　　2.2Transducer Sensitivity</p><p>　　The relationship

13、between 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 transduc

14、er sensitivity is usually known, and, by measuring the output signal, the input quantity is determined from input output-signal increment / K1. </p><p>　　2.3Characteristics of an ideal transducer</p>

15、<p>　　1) high fidelity-the transducer output waveform shape be a faithful reproduction of the measured; there should be minimum distortion.</p><p>　　2) There should be minimum interference with the quan

16、tity being measured; the presence of the transducer should not alter the measured in any way.</p><p>　　3) Size. The transducer must be capable of being placed exactly where it is needed.</p><p>

17、　　4) There should be a linear relationship between the measured and the transducer signal.</p><p>　　5) The transducer should have minimum sensitivity to external effects.</p><p>　　6) The natural

18、 frequency of the transducer should be well separated from the frequency and harmonics of the measurand.</p><p>　　2.4 Photoconductive Cells </p><p>　　The photoconductive cell, uses a light-sensi

19、tive semiconductor material. The resistance between the metal electrodes decrease as the intensity of the light striking the semiconductor increases. Common semiconductor materials used for photo-conductive cells are cad

20、mium sulphide, lead sulphide, and copper-doped germanium. The useful range of frequencies is determined by material used. Cadmium sulphide is mainly suitable for visible light, whereas lead sulphide has its peak response

21、 in the infra-re</p><p>　　3. Optical fiber system</p><p>　　An optical fiber is a flexible, transparent fiber made of glass (silica) or plastic, slightly thicker than a human hair. It can functio

22、n as a waveguide, or “l(fā)ight 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 op

23、tics. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (da</p><p>　　3.1 History </p><p>　　Fiber optics

24、, though used extensively in the modern world, is a fairly simple, and relatively old, technology. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon

25、 and Jacques Babinet in Paris in the early 1840s. John Tyndall included a demonstration of it in his public lectures in London, 12 years later.[3] Tyndall also wrote about the property of total internal reflection in an

26、introductory book about the nature of light in 1</p><p>　　NASA used fiber optics in the television cameras that were sent to the moon. At the time, the use in the cameras was classified confidential, and onl

27、y those with the right security clearance or those accompanied by someone with the right security clearance were permitted to handle the cameras.The crucial attenuation limit of 20 dB/km was first achieved in 1970, by re

28、searchers Robert D. Maurer, Donald Keck, working for American glass maker Corning Glass Works, now Corning Incorporated. They demon</p><p>　　Attenuation in modern optical cables is far less than in electrica

29、l copper cables, leading to long-haul fiber connections with repeater distances of 70–150 kilometers. The erbium-doped fiber amplifier, which reduced the cost of long-distance fiber systems by reducing or eliminating opt

30、ical-electrical-optical repeaters, was co-developed by teams led by David N. Payne of the University of Southampton and Emmanuel Desurvire at Bell Labs in 1986. Robust modern optical fiber uses glass for both core </p

31、><p>　　The emerging field of photonic crystals led to the development in 1991 of photonic-crystal fiber, which guides light by diffraction from a periodic structure, rather than by total internal reflection. Th

32、e first photonic crystal fibers became commercially available in 2000.Photonic crystal fibers can carry higher power than conventional fibers and their wavelength-dependent properties can be manipulated to improve perfor

33、mance.</p><p>　　3.2 Optical fiber communication</p><p>　　Optical fiber can be used as a medium for telecommunication and computer networking because it is flexible and can be bundled as cables.

34、It is especially advantageous for long-distance communications, because light propagates through the fiber with little attenuation compared to electrical cables. This allows long distances to be spanned with few repeater

35、s. Additionally, the per-channel light signals propagating in the fiber have been modulated at rates as high as 111 gigabits per second by NTT,</p><p>　　For short distance application, such as a network in a

36、n office building, fiber-optic cabling can save space in cable ducts. This is because a single fiber can carry much more data than electrical cables such as standard category 5 Ethernet cabling, which typically runs at 1

37、00Mbit/s or 1Gbit/s speeds. Fiber is also immune to electrical interference; there is no cross-talk between signals in different cables, and no pickup of environmental noise. Non-armored fiber cables do not conduct elect

38、ricity</p><p>　　3.3 Other uses of optical fibers</p><p>　　Optical fiber is also used in imaging optics. A coherent bundle of fibers is used, sometimes along with lenses, for a long, thin imaging

39、 device called an endoscope, which is used to view objects through a small hole. Medical endoscopes are used for minimally invasive exploratory or surgical procedures. Industrial endoscopes (see fiberscope or borescope)

40、are used for inspecting anything hard to reach, such as jet engine interiors. </p><p>　　An optical fiber doped with certain rare earth elements such as erbium can be used as the gain medium of a laser or opt

41、ical amplifier. Rare-earth doped optical fibers can be used to provide signal amplification by splicing a short section of doped fiber into a regular (undoped) optical fiber line. The doped fiber is optically pumped with

42、 a second laser wavelength that is coupled into the line in addition to the signal wave. Both wavelengths of light are transmitted through the doped fiber, which</p><p>　　3.4 Principle of operation</p>

43、<p>　　An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis, by the process of total internal reflection. The fiber consists of a core surrounded by a cladding layer, both of w

44、hich are made of dielectric materials. To confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding. The boundary between the core and cladding may either be abrup

45、t, in step-index fiber, or gradual, in graded-index fiber.</p><p>　　3.5 Index of refraction</p><p>　　The index of refraction is a way of measuring the speed of light in a material. Light travels

46、 fastest in a vacuum, such as outer space. The speed of light in a vacuum is about 300,000 kilometers per second. Index of refraction is calculated by dividing the speed of light in a vacuum by the speed of light in some

47、 other medium. The index of refraction of a vacuum is therefore1, by definition. The typical value for the cladding of an optical fiber is 1.52. The core value is typically 1.62. The larg</p><p>　　3.6 Total

48、internal reflection </p><p>　　When light traveling in an optically dense medium hits a boundary at a steep angle (larger than the critical angle for the boundary), the light is completely reflected. Thi

49、s is called total internal reflection. This effect is used in optical fibers to confine light in the core. Light travels through the fiber core, bouncing back and forth off the boundary between the core and cladding. Bec

50、ause the light must strike the boundary with an angle greater than the critical angle, only light that enter</p><p>　　3.7 Multi-mode fiber</p><p>　　Fiber with large core diameter (greater than 1

51、0 micrometers) may be analyzed by geometrical optics. Such fiber is called multi-mode fiber, from the electromagnetic analysis. In a step-index multi-mode fiber, rays of light are guided along the fiber core by total int

52、ernal reflection. Rays that meet the core-cladding boundary at a high angle, greater than the critical angle for this boundary, are completely reflected. The critical angle (minimum angle for total internal reflection) i

53、s determined b</p><p>　　In graded-index fiber, the index of refraction in the core decreases continuously between the axis and the cladding. This causes light rays to bend smoothly as they approach the cladd

54、ing, rather than reflecting abruptly from the core-cladding boundary. The resulting curved paths reduce multi-path dispersion because high angle rays pass more through the lower-index periphery of the core, rather than t

55、he high-index center. The index profile is chosen to minimize the difference in axial propagation</p><p>　　3.8 Single-mode fiber</p><p>　　Fiber with a core diameter less than about ten times the

56、 wavelength of the propagating light cannot be modeled using geometric optics. Instead, it must be analyzed as an electromagnetic structure, by solution of Maxwell's equations as reduced to the electromagnetic wave e

57、quation. As an optical waveguide, the fiber supports one or more confined transverse modes by which light can propagate along the fiber. Fiber supporting only one mode is called single-mode or mono-mode fiber. The behavi

58、or of la</p><p>　　The most common type of single-mode fiber has a core diameter of 8–10 micrometers and is designed for use in the near infrared. The mode structure depends on the wavelength of the light use

59、d, so that this fiber actually supports a small number of additional modes at visible wavelengths. Multi-mode fiber, by comparison, is manufactured with core diameters as small as 50 micrometers and as large as hundreds

60、of micrometers. The normalized frequency V for this fiber should be less than the first zer</p><p>　　3.9 Fiber grating</p><p>　　Fiber grating is one of the most rapid passive optical fiber compo

61、nents in recent years. Since 1978, the year when K. O. Hill and others first used the standing wave writing way in the germanium-doped fiber and make the world's first fiber grating, because of its many unique advant

62、ages, the use of the fiber grating in optical fiber communications Fields and fiber optic sensor Fields are broad prspected. With fiber grating manufacturing technology continues to improve, and the outcome of the appl&l

63、t;/p><p>　　4. Optical fiber sensor </p><p>　　4.1 Optical fiber sensor principle</p><p>　　Based on the traditional sensor is a measurement of the state transition for measurable signals

64、 of the device. Its power supply, sensitive components, receiving signal and processing system and information transmission all use metal wire connection. Optical fiber sensor is a kind of the measurement of the state tr

65、ansition for the light signal can be measured by the device. The transmitter, light sensitive components (optical fiber or the optical fiber), light receptors, signal processing system </p><p>　　Light is an

66、electromagnetic wave, the far infrared wavelengths from extremely the 1mm to a far ultraviolet10nm. Its physical function and biological chemistry because one of the main electric field and cause. Therefore, to discuss t

67、he light sensitive measurement must be consider light of electricity vector of the vibration of the E, namely: A-the amplitude of the vector field E; ω-the vibration frequency;φ-Phi-light phase; T-light transmission time

68、. Visible, if make light intensity, polarization</p><p>　　Fiber optic sensors are often loosely grouped into two basic classes referred to as extrinsic or hybrid fiber optic sensors, and intrinsic or all fib

69、er sensors. Figure 1 illustrates the case of an extrinsic or hybrid fiber optic sensor.</p><p>　　Figure1. Extrinsic fiber optic sensors consist of optical fibers that lead up to and out of a "black box&

70、quot; that modulates the light beam passing through it in response to an environmental effect.</p><p>　　4.2 The classification of the optical fiber sensor</p><p>　　The classification of fiber op

71、tic sensor has some forms, can according to optical fiber sensor in the role of classification, also can according to light modulation of the tested object by the form of classification</p><p>　　4.2.1Accordi

72、ng to the function of optical fiber sensor in classification</p><p>　　Optical fiber sensor into functional, the functional and picked up three types of light type</p><p>　　1).Functional (all fib

73、er type) optical fiber sensor</p><p>　　Use has sensitive to outside information ability and the ability of testing (or special optical fiber optical fiber sensor), will "pass" and "feeling&quo

74、t; integrated sensor. Not only the light on optical fiber effect, and still use of optical fiber in the external factors (bending, phase transformation) function, its optical properties (light intensity, phase, the chang

75、e of polarization, etc.) to realize "pass" and "sense" function. Therefore, the optical fiber sensor is continuous. Due to the conti</p><p>　　2).The functional (or says light-transmission

76、 type) optical fiber sensor</p><p>　　The only light guide fiber role, "the" not only "sense" to outside information, "feel" function depend on other physical properties of funct

77、ional component finish. Optical fiber discontinuous. This kind of optical fiber sensor to need not special optical fiber and other special technology, much easier to achieve, and the cost is low. But sensitivity is low,

78、the sensitivity requirement is not too high for the occasion.</p><p>　　3).Pick up the light fiber-optic sensor</p><p>　　With optical fiber probe, as received from tested object radiation light o

79、r be its reflection, scattering of light. Its typical examples such as optical fiber laser doppler velocity gauge, FuSheShi optical fiber temperature sensors, etc.</p><p>　　4.2.2According to the form of ligh

80、t modulated by the object being measured</p><p>　　1).Intensity modulation fiber-optic sensors</p><p>　　It is a use of tested object of the change sensitive components the refractive index, absor

81、b or reflection of the parameters such as changes, and lead to the light intensity changes to achieve sensitive sensors measuring. Use of optical fiber bending loss of micro; The material of the absorption characteristic

82、s; Vibration film or LCD reflected light intensity change; Material because of all sorts of particle rays or chemical, mechanical incentive and shine phenomenon; And the material of the flu</p><p>　　2).Polar

83、ization modulation fiber-optic sensors</p><p>　　It is a kind of polarization of light changes to deliver the tested object information of the sensor. Favorable light in magnetic field in the medium of the sp

84、read of Faraday effect of current, magnetic field sensors made; Use light in the electric field spread a piezoelectric crystal of the bubble's effect of the electric field, make voltage sensor; The light of the use o

85、f matter the effect of pressure, vibration or a sound sensors; And the use of optical fiber birefringence sex constitute the </p><p>　　3).Frequency modulation fiber-optic sensors</p><p>　　It is

86、a use of monochromatic shot to the object to be tested the reflected light changes the frequency of the monitor to the sensor. Use of sports objects reflect light and scattering light doppler effect of the optical fiber

87、speed, vibration, pressure, flow velocity and acceleration sensors; By using material glare of the Raman scattering when a measuring gas concentration or monitoring air pollution gas sensors; And the use of organic light

88、 of the temperature sensor, etc.</p><p>　　4).Phase modulation sensor</p><p>　　Its basic principle is to use tested object to sensitive components in the role of the sensitive components of the r

89、efractive index or the transmission constant change, and lead to the phase of the light change, make the two beams of the interference fringes monochromatic produces change, through the test of the interference streak to

90、 determine the amount of variation of the light of phase change, and get tested object of information. Usually run out of the favorable effect sound, pressure or vi</p><p>　　4.3 The applications of OFS</p

91、><p>　　Fibers have many uses in remote sensing. In some applications, the sensor is itself an optical fiber. In other cases, fiber is used to connect a non-fiberoptic sensor to a measurement system. Depending o

92、n the application, fiber may be used because of its small size, or the fact that no electrical power is needed at the remote location, or because many sensors can be multiplexed along the length of a fiber by using diffe

93、rent wavelengths of light for each sensor, or by sensing the time delay as li</p><p>　　Optical fibers can be used as sensors to measure strain, temperature, pressure and other quantities by modifying a fiber

94、 so that the property to measure modulates the intensity, phase, polarization, wavelength, or transit time of light in the fiber. Sensors that vary the intensity of light are the simplest, since only a simple source and

95、detector are required. A particularly useful feature of such fiber optic sensors is that they can, if required, provide distributed sensing over distances of up</p><p>　　Extrinsic fiber optic sensors use an

96、optical fiber cable, normally a multi-mode one, to transmit modulated light from either a non-fiber optical sensor—or an electronic sensor connected to an optical transmitter. A major benefit of extrinsic sensors is thei

97、r ability to reach otherwise inaccessible places. An example is the measurement of temperature inside aircraft jet engines by using a fiber to transmit radiation into a radiation pyrometer outside the engine. Extrinsic s

98、ensors can be used in t</p><p>　　Common uses for fiber optic sensors includes advanced intrusion detection security systems. The light is transmitted along a fiber optic sensor cable placed on a fence, pipel

99、ine, or communication cabling, and the returned signal is monitored and analysed for disturbances. This return signal is digitally processed to detect disturbances and trip an alarm if an intrusion has occurred.</p>