光纤传感器的应用研究(中英对照)

光纤传感器的应用研究

摘 要 本文介绍了光纤传感器研究的目的、意义及其发展趋势，通过分析研究各类光纤传感器的基本原理，设计出了几种功能较完善的光纤传感器。首先从研究光纤传感器的工作原理出发，分析各种光纤传感器的结构和原理，通过对原有光纤传感器的结构和控制机理的分析，结合学过的电子知识，设计光纤传感温度计、光纤传感压强计等。在整个研究过程中采取实验和理论相结合的方式。

1绪论

光纤传感器是70年代末发展起来的一种新型传感器，它具有不受电磁场影响，本

质上安全防爆，体积小，耐腐蚀，灵敏度高等优点。可用在传统传感器难以涉足的极端恶劣环境，所以在军事、航空航天、生物医学、建筑施工等领域被受青睐。因此对光纤传感器的研究具有很重要的现实意义。传感技术是近几年热门的应用技术，传感器在朝着灵敏、精确、适应性强、小巧和智慧化的方向发展。在这一过程中，光纤传感器这个传感器家族的新成员倍受青睐。光纤具有很多优异的性能，例如：抗电磁干扰和原子辐射的性能， 径细、质软、重量轻的机械性能，绝缘、无感应的电气性能，耐水、耐高温、耐腐蚀的化学性能等，它能够在人达不到的地方（如高温区），或者对人有害的地区（如核辐射区），起到人的耳目的作用，而且还 能超越人的生理界限，接收人的感官所感受不到的外界信息。光纤传感器是最近几年出现的新技术，可以用来测量多种物理量，比如声场、电场、压力、温度、角速度、加速度等，还可以完成现有测量技术难以完成的测量任务。在狭小的空间里，在强电磁干扰和高电压的环境里，光纤传感器都显示出了独特的魅力。因此，光纤传感技术应用的研究具有很好的前景。光纤传感优点：灵敏度较高；几何形状具有多方面的适应性，可以制成任意形状的光纤传感器；可以制造传感各种不同物理信息（声、磁、温度、旋转等）的器件；可以用于高压、电气噪声、高温、腐蚀、或其它的恶劣环境；而且具有与光纤遥测技术的内在相容性。

光纤传感器用光作为敏感信息的载体，用光纤作为传递敏感信息的媒质。因此，它同时具有光纤及光学测量的特点。 ①电绝缘性能好。 ②抗电磁干扰能力强。 ③非侵入性。 ④高灵敏度。

- 1 -

⑤容易实现对被测信号的远距离监控

2光通信简介

2.1有线光通信

有线光通信的传输媒介为光纤。光纤是光导纤维的简称，是用光透射率高的电介质构成的光通路。它是一种介质圆柱光波导。所谓“光波导”是指将以光的形式出现的电磁波能量利用全反射的原理约束并引导光波在光纤内部或表面附近沿轴线方向传播。

2.2 无线光通信

无线光通信系统（FSO）以大气作为传输媒质来进行光信号的传送。只要在适当距离的收发两个端机之间存在无遮挡的视距路径和足够的光发射功率，即可实现无线光通信。

3光纤传感器简介

3.1光纤传感器的结构原理

以电为基础的传统传感器是一种把测量的状态转变为可测的电信号的装置。它的电源、

敏感元件、信号接收和处理系统以及信息传输均用金属导线连接，见图(a)。光纤传感器则是一种把被测量的状态转变为可测的光信号的装置。由光发送器、敏感元件(光纤或非光纤的)、光接收器、信号处理系统以及光纤构成由光发送器发出的光经源光纤引导至敏感元件。这时，光的某一性质受到被测量的调制，已调光经接收光纤耦合到光接收器，使光信号变为电信号，最后经信号处理得到所期待的被测量。

可见,光纤传感器与以电为基础的传统传感器相比较，在测量原理上有本质的差别。传统传感器是以机—电测量为基础，而光纤传感器则以光学测量为基础。

光是一种电磁波，其波长从极远红外的lmm到极远紫外线的10nm。它的物理作用和生物化学作用主要因其中的电场而引起。因此，讨论光的敏感测量必须考虑光的电矢量E的振动，即

A——电场E的振幅矢量；ω——光波的振动频率；

- 2 -

φ——光相位；t——光的传播时间。

可见，只要使光的强度、偏振态(矢量A的方向)、频率和相位等参量之一随被测量状态的变化而变化，或受被测量调制，那么，通过对光的强度调制、偏振调制、频率调制或相位调制等进行解调，获得所需要的被测量的信息。

3.2光纤传感器的分类

光纤传感器的分类有多种形式，可以根据光纤在传感器中的作用进行分类，也可以根据光受被测对象的调制形式进行分类 3.2.1根据光纤在传感器中的作用分类

光纤传感器分为功能型、非功能型和拾光型三大类。 1）功能型（全光纤型）光纤传感器

利用对外界信息具有敏感能力和检测能力的光纤(或特殊光纤)作传感元件，将“传”和“感”合为一体的传感器。光纤不仅起传光作用，而且还利用光纤在外界因素(弯曲、相变)的作用下，其光学特性(光强、相位、偏振态等)的变化来实现“传”和“感”的功能。因此，传感器中光纤是连续的。由于光纤连续，增加其长度，可提高灵敏度。

光发送器光纤敏感元件 信号处理 光受信器

2）非功能型（或称传光型）光纤传感器

光纤仅起导光作用，只“传”不“感”，对外界信息的“感觉”功能依靠其他物理性质的功能元 - 3 -

件完成。光纤不连续。此类光纤传感器无需特殊光纤及其他特殊技术，比较容易实现，成本低。但灵敏度也较低，用于对灵敏度要求不太高的场合。 3）拾光型光纤传感器

用光纤作为探头，接收由被测对象辐射的光或被其反射、散射的光。其典型例子如光纤激光多普勒速度计、辐射式光纤温度传感器等。 3.2.2根据光受被测对象的调制形式分类 （1）强度调制型光纤传感器

是一种利用被测对象的变化引起敏感元件的折射率、吸收或反射等参数的变化，而导致光强度变化来实现敏感测量的传感器。有利用光纤的微弯损耗；各物质的吸收特性；振动膜或液晶的反射光强度的变化；物质因各种粒子射线或化学、机械的激励而发光的现象；以及物质的荧光辐射或光路的遮断等来构成压力、振动、温度、位移、气体等各种强度调制型光纤传感器。

优点：结构简单、容易实现，成本低。

缺点：受光源强度波动和连接器损耗变化等影响较大 。 （2）偏振调制光纤传感器

是一种利用光偏振态变化来传递被测对象信息的传感器。有利用光在磁场中媒质内传播的法拉第效应做成的电流、磁场传感器；利用光在电场中的压电晶体内传播的泡尔效应做成的电场、电压传感器；利用物质的光弹效应构成的压力、振动或声传感器；以及利用光纤的双折射性构成温度、压力、振动等传感器。这类传感器可以避免光源强度变化的影啊，因此灵敏度高。 （3）频率调制光纤传感器

是一种利用单色光射到被测物体上反射回来的光的频率发生变化来进行监测的传感器。有利用运动物体反射光和散射光的多普勒效应的光纤速度、流速、振动、压力、加速度传感器；利用物质受强光照射时的喇曼散射构成的测量气体浓度或监测大气污染的气体传感器；以及利用光致发光的温度传感器等。

（4）相位调制传感器

其基本原理是利用被测对象对敏感元件的作用，使敏感元件的折射率或传播常数发生变化，而导致光的相位变化，使两束单色光所产生的干涉条纹发生变化，通过检测干 - 4 -

涉条纹的变化量来确定光的相位变化量，从而得到被测对象的信息。通常有利用光弹效应的声、压力或振动传感器；利用磁致伸缩效应的电流、磁场传感器；利用电致伸缩的电场、电压传感器以及利用光纤赛格纳克（Sagnac）效应的旋转角速度传感器（光纤陀螺）等。这类传感器的灵敏度很高。但由于须用特殊光纤及高精度检测系统，因此成本高。

4光纤传感温度计的设计

这里我们设计的是透射型半导体光纤温度传感器。

当一束白光经过半导体晶体片时，低于某个特定波长λg的光将被半导体吸收,而高于该波长的光将透过半导体。这是由于半导体的本征吸收引起的,λg称为半导体的本征吸收波长。电子从价带激发到导带引起的吸收称为本征吸收。当一定波长的光照射到半导体上时,电子吸收光能从价带跃迁入导带,显然,要发生本征吸收,光子能量必须大于半导体的禁带宽度Eg，即

h Eg

h —普朗克常数；v —光频率 因λ＝c/v，则产生本征吸收条件： ，即

gh EghcEg

h —普朗克常数；v —光频率 因λ＝c/v，则产生本征吸收条件： hc Eg因此，对于波长大于λg的光，

g因此，对于波长大于λg的光，能透过半导体，而波长小于λg的光将被半导体吸收。不同种类的半导体材料具有不同的本征吸收波长，图为在室温(20℃)时,120μm厚的GaAs材料的透射率曲线。 GaAs在室温时的本征吸收波长约为880nm左右，半导体的吸收光谱与Eg有关，而半导体材料的Eg随温度的不同而不同，Eg与温度t的关系可表示为： t2EgtEg0t

- 5 -

式中：Eg（0）——绝对零度时半导体的禁带宽度；

α——经验常数(eV／K)；β——经验常数(K)。 对于GaAs材料，由实验得到 α =5.8×10-4eV/K β=300K

由此可见，半导体材料的Eg随温度上升而减小，亦即其本征吸收波长λg随温度上升而增大。反映在半导体的透光特性上，即当温度升高时，其透射率曲线将向长波方向移动。若采用发射光谱与半导体的λg(t)相匹配的发光二极管作为光源，则透射光强度将随着温度的升高而减小。即通过检测透射光的强度或透射率，即可检测温度变化。

- 6 -

Eg01.522eV

The application of optical fiber sensor

Abstract: This paper describes the purpose of researching on FOS and its development. Based on the principle of all kinds of FOS，finishing some good function FOS.Firstly，we study the principle of FOS which helps me know the structure and theory.Secondly，because of the anlysis of the old FOS’framework，we combine some electric knowledge to design a fiber pressure sensor and a fiber temperature pressure.Between the whole course of the research，we take the measure of experimentation and theory studying.

1. Introduction

Optical fiber sensor is developed at the end of 70 s as a new type of sensor, it has not affected by electromagnetic 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, aviation, biological medicine, building construction field is popular. So to optical fiber sensor research has very important practical significance. Sensing technology 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 excellent 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 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 technology in recent years, can be used to measure DuoZhong 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 electromagnetic interference and high voltage environment, optical fiber sensors shows the unique charm. Therefore, the optical fiber sensing technology application research has the very good prospects. The optical fiber sensing advantage: high sensitivity; Geometric shape has many aspects of adaptability, can be made into any shape of the optical fiber sensor; Can manufacture various physical sensor information (sound, magnetic, temperature, rotation, etc.) of the device; Can be used for high pressure, electrical noise, high temperature, corrosion, or other harsh environment; But has the optical fiber sensing and the internal compatibility.

Optical fiber sensor light sensitive information carrier, as the optical fibre as sensitive information 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 signal remote monitoring

- 7 -

2. Optical communication introduction

2.1 Optical cable

Cable of the transmission medium for optical fiber optical communication. Optical fiber is the abbreviation of optical fiber transmission rate is light, high dielectric consists of the light path. It is a kind of dielectric column optical waveguide. The so-called \"optical waveguide\" means in the form of light will be of electromagnetic energy use the principle of total reflection constraint and the waves in optical fiber guide inside or near the surface along the axis direction spread

2.2 Wireless Optical Communication

FSO system (FSO) to the atmosphere as a transmission medium to light signals transmitted. As long as the proper distance in the sending and receiving two end between machine without sunscreen, beyond the path and enough light transmission power, can realize the wireless optical communication

3. Optical fiber sensor profile

3.1 Optical fiber sensor structure principle

Based on the traditional sensor is a measurement of the state transition for measurable signals of the device. Its power supply, sensitive components, receiving signal and processing system and information transmission all use metal wire connection, see chart (a). Optical fiber sensor is a kind of the measurement of the state transition 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 and the optical fiber by light a transmitter the light source of the optical fiber guide to sensitive components. At this time, the light of a certain property is measured by the regulation, already light receiving the coupling to light receptors, make the light signal into electrical signals, and finally get the signal processing to be measured.

Visible, optical fiber sensor and to call for the traditional sensor based compared in measuring principle, have fundamentally different. Traditional sensor in machine, electricity measurement for the foundation, and the optical fiber sensor is based on optical measurement.

Light is an electromagnetic wave, the far infrared wavelengths from extremely the LMM to a far ultraviolet 10 nm. Its physical function and biological chemistry because one of the main electric field and cause. Therefore, to discuss the 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; Omega of the waves of light-the vibration frequency; Phi-light phase; T-light transmission time.

Visible, if make light intensity, polarization direction of A (vector), frequency and phase one of the parameters such as with the change of state is measured and change, or is measured by A, then, through the light intensity modulation, polarization modulation frequency modulation, or phase modulation of demodulation, gain needed be measured information. 3.2 The classification of the optical fiber sensor

The classification of fiber optic sensor has DuoZhong form, can according to optical fiber sensor

in the role of classification, can also according to light modulation of the tested object by the - 8 -

form

of classification

3.2.1According to the function of optical fiber sensor in classification

Optical fiber sensor into functional, the functional and picked up three types of light type 1).Functional (all fiber type) optical fiber sensor

Use has sensitive to outside information ability and the ability of testing (or special optical fiber optical fiber sensor), will \"pass\" and \"feeling\" 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 change of polarization, etc.) to realize \"pass\" and \"sense\" function. Therefore, the optical fiber sensor is continuous. Due to the continuous fiber, increase its length, can improve the sensitivity

Light transmitter Optical fiber sensing elements Signal processing Light accept the signal

2).The functional (or says light-transmission type) optical fiber sensor

The only light guide fiber role, \"the\" not only \"sense\" to outside information, \"feel\" function depend on other physical properties of functional 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, the sensitivity requirement is not too high for the occasion.

3).Pick up the light fiber-optic sensor

With optical fiber probe, as received from tested object radiation light or be its reflection, scattering of light. Its typical examples such as optical fiber laser doppler velocity gauge, FuSheShi optical fiber temperature sensors, etc. 3.2.2 Intensity modulation fiber-optic sensors

It is a use of tested object of the change sensitive components the refractive index, absorb 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 characteristics; Vibration film or LCD reflected light intensity change; Material because of all sorts of particle rays or chemical, mechanical incentive and shine phenomenon; - 9 -

And the material of the fluorescent light radiation or the road block to form such as pressure, vibration, temperature, displacement, gas, etc. Various kinds of intensity modulation fiber-optic sensors.

Advantages: simple structure and easy to implement, and the cost is low. Faults: light intensity by fluctuations and connectors loss of changes greatly. (2).Polarization modulation fiber-optic sensors

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 spread 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 of matter the effect of pressure, vibration or a sound sensors; And the use of optical fiber birefringence sex constitute the temperature, pressure, vibration for the sensor. This kind of sensor can avoid light source of strength changes of ah, so high sensitivity. (3).Frequency modulation fiber-optic sensors

It is 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 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 of the temperature sensor, etc.

Phase modulation sensor

(4).he basic principle is to use tested object to sensitive components in the role of the sensitive components of the refractive 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 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 vibration sensor; Use magnetostrictive effect of the current, magnetic field sensors; Use electricity to the electric field, adjustable voltage sensor and the use of optical fiber, g (Sagnac stablished) effect of angular velocity sensor (optical fiber gyro), etc. This kind of sensor sensitivity high. But because must use special optical fiber and high precision testing system, so the cost is high.

4.The design of optical fiber sensing a thermometer

Here we design type semiconductor optical fiber transmission is the temperature sensor.

hcWhen a bunch of white light after a little while, and semiconductor crystals fall below a certain gEgwavelengths of light lambda g will be semiconductor absorb, and higher than the wavelengths of light through the semiconductor. This is because the semiconductor the eigenvalue of the absorption of the cause, lambda g called semiconductor the eigenvalue of the absorption wavelength. Electronic valence band inspired to guide from with the absorption of the eigenvalue called cause absorption. When certain wavelengths of light to illuminate the semiconductor, electronic absorb the light from the price jump with having the conduction band, obviously, to happen on the absorption, photon energy must be greater than the width of the semiconductor with Eg, namely

- 10 -

h  Eg

Produce the kind of absorption conditions：

gh  EghcEg

H-Planck's constant; V-light frequencies For lambda = c/v, it produces

So, for the wavelength of the light, greater than the lambda g

So, for the wavelength of the light, greater than the lambda g can pass through, and less than the wavelength semiconductor light will be lambda g semiconductor absorption. Different kinds of semiconductor materials have different the eigenvalue of the absorption wavelength, the graph is in room temperature (20 ℃), 120 mu m thick GaAs transmission rate curve of the material. GaAs at room temperature absorbed the eigenvalue of the wavelengths of about 880 nm or so, the absorption spectra of the semiconductor and Eg, semiconductor materials about the Eg with temperature different and different, Eg and the relationship between temperature t can be expressed as:

t2EgtEg0t

This shows, Eg of semiconductor materials with temperature increasing and decreases, and that is the kind of the absorption wave lambda g increases with temperature increasing. Reflected in the semiconductor in characteristics, and that is when the pervious to light the temperature rises, the transmission rate curve will long to direction. If you use the emission spectrum and semiconductor lambda g (t) matching leds as the light source, the transmission light intensity will decrease with the rise of temperature. That is, through the test of strength or transmitted light transmission rate, can testing temperature changes.

- 11 -