CN105911025A - Distributed spiral core optical fiber surface plasmon resonance sensor and measurement method thereof - Google Patents
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Abstract
本发明提供了一种分布式螺旋芯光纤表面等离子体共振传感器及其测量方法，传感器包括宽谱光源、光纤传感单元和光谱仪，宽谱光源与光纤传感单元的输入端连接，光纤传感单元的输出端与光谱仪连接，光纤传感单元由一段螺旋芯光纤和一段表面镀有敏感金属薄膜的无芯光纤构成的周期性结构组成。测量方法通过在光谱仪中检测到的表面等离子体共振波谱来判断传感单元中无芯光纤的外介质的折射率；当无芯光纤的外介质的折射率增大时，共振波长增大；外介质折射率减小时，共振波长减小；将光源换成波长在表面等离子体共振波长附近的光源，用背向散射法确定发生表面等离子体共振的位置。本发明提高了能量利用率，灵敏度高，检测难度低，能实现分布式检测。
The invention provides a distributed helical core optical fiber surface plasmon resonance sensor and its measurement method. The sensor includes a wide-spectrum light source, an optical fiber sensing unit and a spectrometer. The wide-spectrum light source is connected to the input end of the optical fiber sensing unit, and the optical fiber sensing unit The output end of the unit is connected with the spectrometer, and the optical fiber sensing unit is composed of a periodical structure composed of a section of spiral core optical fiber and a section of coreless optical fiber coated with a sensitive metal film on the surface. The measurement method judges the refractive index of the outer medium of the coreless fiber in the sensing unit through the surface plasmon resonance spectrum detected in the spectrometer; when the refractive index of the outer medium of the coreless fiber increases, the resonance wavelength increases; When the refractive index of the medium decreases, the resonance wavelength decreases; the light source is replaced with a light source with a wavelength near the surface plasmon resonance wavelength, and the position where the surface plasmon resonance occurs is determined by the backscattering method. The invention improves the energy utilization rate, has high sensitivity, low detection difficulty and can realize distributed detection.
Description
技术领域technical field
本发明涉及光纤表面等离子体共振传感器的装置，具体涉及一种分布式螺旋芯光纤表面等离子体共振传感器及其测量方法。The invention relates to a device for an optical fiber surface plasmon resonance sensor, in particular to a distributed helical core optical fiber surface plasmon resonance sensor and a measuring method thereof.
背景技术Background technique
目前光纤表面等离子体共振传感器大概分为去包层类、锥形或楔形探针类、异芯光纤类这三类。其中，去包层类在去包层时一致性难以控制，锥形或楔形探针类在对切割角处理时所需要的切割、抛光和镀膜工艺都非常高，异芯光纤类，也就是多模-单模-多模光纤类，这类光纤不需要去包层、抛光、控制切割角等繁琐的工艺，使得光纤生产成本大大降低。这种光纤利用多模光纤的纤芯大于单模光纤纤芯的特点，当光从多模光纤的纤芯传导进入单模光纤的时候，光会大量泄漏进入到单模光纤的包层中，并在单模光纤的包层和外介质的界面上发生全反射并产生倏逝波，如果在单模光纤的包层外面镀上敏感金属薄膜就能产生表面等离子体共振效应。当单模光纤的外介质改变时，相应的表面等离子体共振波谱也会改变。我们可以根据这种效应测量不同的外介质。At present, optical fiber surface plasmon resonance sensors can be roughly divided into three types: decladding type, tapered or wedge-shaped probe type, and heterocore optical fiber type. Among them, it is difficult to control the consistency of the decladding type when decladding, and the cutting, polishing and coating processes required for the cutting angle of the tapered or wedge-shaped probe are very high. Mode-single-mode-multimode optical fiber, this type of optical fiber does not need cumbersome processes such as de-cladding, polishing, and control of cutting angle, which greatly reduces the production cost of optical fiber. This fiber utilizes the characteristic that the core of the multimode fiber is larger than the core of the single-mode fiber. When light is transmitted from the core of the multimode fiber into the single-mode fiber, a large amount of light will leak into the cladding of the single-mode fiber. And total reflection occurs at the interface between the cladding of the single-mode fiber and the outer medium and evanescent waves are generated. If a sensitive metal film is coated on the outside of the cladding of the single-mode fiber, the surface plasmon resonance effect can be produced. When the outer medium of a single-mode fiber changes, the corresponding surface plasmon resonance spectrum will also change. We can measure different external media according to this effect.
然而，多模光纤中存在很多不同传导模式的光，这些不同模式的光会以不同的角度泄露进单模光纤，并且在单模光纤的包层和外介质表面发生全反射时的角度也不同，那么不同的全反射角也会对应不同的表面等离子体共振波谱。也就是说，最终测量到的共振波谱实际是多模光纤中不同模式所激发的共振波谱的叠加谱。这样就会最终导致测量到的共振波谱的半高宽降低，测量灵敏度降低。而单模光纤-无芯光纤-单模光纤结构会因为单模光纤的纤芯横截面积远小于包层而导致光从无芯光纤耦合进单模光纤时损失太大，降低了能量利用率，使之无法构成分布式系统。However, there are many different modes of light in the multimode fiber, and these different modes of light will leak into the single-mode fiber at different angles, and the angles at which total reflection occurs on the cladding and outer medium surface of the single-mode fiber are also different. , then different total reflection angles will also correspond to different surface plasmon resonance spectra. That is to say, the finally measured resonance spectrum is actually a superposition spectrum of resonance spectra excited by different modes in the multimode fiber. This will eventually lead to a decrease in the half-width of the measured resonance spectrum and a decrease in measurement sensitivity. However, the single-mode fiber-coreless fiber-single-mode fiber structure will cause too much loss when the light is coupled from the coreless fiber into the single-mode fiber because the core cross-sectional area of the single-mode fiber is much smaller than the cladding, which reduces the energy utilization rate. , making it impossible to form a distributed system.
发明内容Contents of the invention
本发明要解决的技术问题是，针对现有技术存在的上述不足，提供一种分布式螺旋芯光纤表面等离子体共振传感器及其测量方法，基于表面等离子体共振效应的分布式螺旋芯光纤-无芯光纤结构，提高了能量利用率，灵敏度高，检测难度低，能实现分布式检测。The technical problem to be solved by the present invention is to provide a distributed helical core optical fiber surface plasmon resonance sensor and its measurement method for the above-mentioned deficiencies in the prior art. The core fiber structure improves energy utilization, high sensitivity, low detection difficulty, and can realize distributed detection.
本发明为解决上述技术问题所采用的技术方案是：The technical scheme that the present invention adopts for solving the problems of the technologies described above is:
一种分布式螺旋芯光纤表面等离子体共振传感器，包括宽谱光源、光纤传感单元和光谱仪，所述宽谱光源与光纤传感单元的输入端连接，光纤传感单元的输出端与光谱仪连接，所述光纤传感单元由一段螺旋芯光纤和一段表面镀有敏感金属薄膜的无芯光纤构成的周期性结构组成，每个周期内敏感金属薄膜的起点为螺旋芯光纤和无芯光纤的熔接点，敏感金属薄膜的终点为无芯光纤和螺旋芯光纤的熔接点。A distributed helical core optical fiber surface plasmon resonance sensor, comprising a broadband light source, an optical fiber sensing unit and a spectrometer, the broadband light source is connected to the input end of the optical fiber sensing unit, and the output end of the optical fiber sensing unit is connected to the spectrometer , the optical fiber sensing unit is composed of a periodical structure consisting of a section of spiral-core optical fiber and a section of coreless optical fiber coated with a sensitive metal film on the surface, and the starting point of the sensitive metal film in each period is the fusion of the spiral-core optical fiber and the coreless optical fiber The end point of the sensitive metal film is the fusion point of the coreless fiber and the spiral core fiber.
按上述方案，所述无芯光纤为去掉涂覆层的折射率一定的光纤。According to the above solution, the coreless optical fiber is an optical fiber with a constant refractive index without the coating layer.
按上述方案，所述敏感金属薄膜包括纳米金属薄膜、纳米金属氧化物薄膜、纳米合金薄膜及其他对湿度、温度、浓度、应力敏感的功能性及特异性材料薄膜。According to the above solution, the sensitive metal film includes nano metal film, nano metal oxide film, nano alloy film and other functional and specific material films sensitive to humidity, temperature, concentration and stress.
按上述方案，所述宽谱光源为波长在400～1800nm范围内连续变化的无突变的连续谱白光激光光源。According to the above scheme, the wide-spectrum light source is a continuous-spectrum white-light laser light source with a wavelength continuously changing in the range of 400-1800 nm without sudden change.
按上述方案，所述光谱仪为检测波长范围400～1800nm光强的光谱仪，检测灵敏度小于1nm。According to the above solution, the spectrometer is a spectrometer for detecting light intensity in a wavelength range of 400-1800 nm, and the detection sensitivity is less than 1 nm.
本发明还提供了一种上述分布式螺旋芯光纤表面等离子体共振传感器的测量方法，包括如下步骤：The present invention also provides a measurement method for the above-mentioned distributed helical-core optical fiber surface plasmon resonance sensor, comprising the following steps:
1)通过在光谱仪中检测到的表面等离子体共振波谱来判断光纤传感单元中无芯光纤的外介质的折射率；1) judge the refractive index of the outer medium of the coreless optical fiber in the optical fiber sensing unit by the surface plasmon resonance spectrum detected in the spectrometer;
2)当无芯光纤的外介质的折射率增大时，共振波长增大；当无芯光纤的外介质折射率减小时，共振波长减小；2) When the refractive index of the outer medium of the coreless fiber increases, the resonance wavelength increases; when the refractive index of the outer medium of the coreless fiber decreases, the resonance wavelength decreases;
3)将宽谱光源换成波长在表面等离子体共振波长附近的光源，用背向散射法确定发生表面等离子体共振的位置。3) Replace the wide-spectrum light source with a light source with a wavelength near the wavelength of the surface plasmon resonance, and use the backscattering method to determine the position where the surface plasmon resonance occurs.
按上述方案，所述步骤3)中，如果不发生表面等离子体共振现象，则测得的反射光功率随着时间的增长而缓慢减小；如果在某处发生表面等离子体共振现象，光传播到该处时背向散射光急剧减小，通过背向散射光急剧减小的现象测得发生表面等离子体共振现象的位置。According to the above scheme, in the step 3), if the surface plasmon resonance phenomenon does not occur, the measured reflected optical power slowly decreases with the increase of time; if the surface plasmon resonance phenomenon occurs somewhere, the light propagation When reaching this place, the backscattered light decreases sharply, and the position where the surface plasmon resonance phenomenon occurs is measured by the phenomenon of the sharp decrease of the backscattered light.
本发明的工作原理：使用一段螺旋芯光纤作为传光光纤，无芯光纤作为传感单元。当宽谱光源发出的光耦合进入螺旋芯光纤后，由于螺旋芯光纤的纤芯弯曲结构使得高阶模式的光在传输的过程中快速损耗，而基模的能量几乎不会损耗。对于无芯光纤而言，它和外介质一起构成了光密-光疏结构，也就是说无芯光纤相当于一段多模光纤的纤芯，外介质相当于多模光纤的包层。当螺旋芯光纤的基模光耦合进入无芯光纤时，会在无芯光纤中激发多个模式的光。其中被激发的基模光会直接通过无芯光纤进入到下一段螺旋芯光纤中，而高阶模式的光会在无芯光纤的包层和外介质的交界面发生全反射并产生倏逝波，在无芯光纤的包层外侧镀上敏感金属薄膜会增大倏逝波的横向波矢，当入射光的波长满足共振条件时就能发生表面等离子体共振现象。当外介质的介电常数改变时，对应的共振波长也会改变。基于这一现象可以测量不同的外介质。如果某一位置的气体浓度发生改变时，在光谱仪中检测到多个吸收峰，在观察到有多个吸收峰的情况下，使用对应的共振波长附近的光源作为入射光源，再用背向散射法测得发生表面等离子体共振的位置。The working principle of the present invention is as follows: a section of spiral-core optical fiber is used as the light-transmitting optical fiber, and a coreless optical fiber is used as the sensing unit. When the light emitted by the broadband light source is coupled into the helical core fiber, due to the bent structure of the core of the helical core fiber, the light of the high-order mode is rapidly lost during transmission, and the energy of the fundamental mode is almost not lost. For a coreless fiber, it forms an optically dense-optical sparse structure together with the outer medium, that is to say, the coreless fiber is equivalent to the core of a section of multimode fiber, and the outer medium is equivalent to the cladding of the multimode fiber. When the fundamental mode light of the spiral core fiber is coupled into the coreless fiber, multiple modes of light are excited in the coreless fiber. The excited fundamental mode light will directly enter the next spiral core fiber through the coreless fiber, while the high-order mode light will be totally reflected at the interface between the cladding of the coreless fiber and the outer medium and generate evanescent waves. , Coating a sensitive metal film on the outside of the cladding of the coreless fiber will increase the transverse wave vector of the evanescent wave, and the surface plasmon resonance phenomenon will occur when the wavelength of the incident light satisfies the resonance condition. When the dielectric constant of the external medium changes, the corresponding resonance wavelength also changes. Based on this phenomenon, different external media can be measured. If the gas concentration at a certain position changes, multiple absorption peaks are detected in the spectrometer, and when multiple absorption peaks are observed, use a light source near the corresponding resonance wavelength as the incident light source, and then use backscattering The location of the surface plasmon resonance was determined by the method.
本发明相比于传统的光纤表面等离子体共振传感器，具有以下有益效果：Compared with the traditional optical fiber surface plasmon resonance sensor, the present invention has the following beneficial effects:
1、相对于去包层类的光纤表面等离子体共振传感器而言，本发明不需要去包层，因此不存在去包层的过程中存在的腐蚀程度难以控制，腐蚀之后的光纤表面难以抛光等问题；1. Compared with decladding optical fiber surface plasmon resonance sensors, the present invention does not require decladding, so the degree of corrosion in the process of decladding is difficult to control, and the surface of the optical fiber after corrosion is difficult to polish, etc. question;
2、相比于锥形或楔形探针表面等离子体共振传感器而言，本发明不需要控制光纤端口的切割角或锥形角，也不需要抛光等工艺；2. Compared with the tapered or wedge-shaped probe surface plasmon resonance sensor, the present invention does not need to control the cutting angle or taper angle of the fiber port, nor does it need polishing and other processes;
3、相比于多模光纤-单模光纤-多模光纤表面等离子体共振传感器而言，由于使用了螺旋芯光纤和无芯光纤，使得本发明不存在用多模光纤传导入射光时存在的多模光纤中模式众多且难以控制的问题；3. Compared with the multimode fiber-single-mode fiber-multimode fiber surface plasmon resonance sensor, due to the use of spiral core fiber and coreless fiber, the present invention does not have the problem of using multimode fiber to transmit incident light. The problem that there are many modes in multimode fiber and it is difficult to control;
4、相比于单模光纤-无芯光纤-单模光纤表面等离子体共振传感器而言，由于本发明所使用的螺旋芯光纤和多模光纤的纤芯直径大于单模光纤，使得入射光的能量和出射光的能量都高于单模光纤-无芯光纤-单模光纤表面等离子体共振传感器，因而提高了能量利用率，灵敏度高，检测难度低，能实现分布式检测。4. Compared with the single-mode optical fiber-coreless optical fiber-single-mode optical fiber surface plasmon resonance sensor, since the core diameter of the spiral-core optical fiber and multi-mode optical fiber used in the present invention is larger than that of the single-mode optical fiber, the incident light Both the energy and the energy of the emitted light are higher than that of the single-mode fiber-coreless fiber-single-mode fiber surface plasmon resonance sensor, thus improving the energy utilization rate, high sensitivity, low detection difficulty, and can realize distributed detection.
附图说明Description of drawings
图1是本发明分布式螺旋芯光纤表面等离子体共振传感器的结构示意图；Fig. 1 is a schematic structural view of a distributed helical-core optical fiber surface plasmon resonance sensor of the present invention;
图2是图1中光纤传感单元的结构示意图；Fig. 2 is a schematic structural view of the optical fiber sensing unit in Fig. 1;
图3是本发明的归一化光谱只有一个吸收峰的结构示意图；Fig. 3 is the structural representation that the normalized spectrum of the present invention has only one absorption peak;
图4是本发明的归一化光谱有多个吸收峰的结构示意图；Fig. 4 is the structural representation that the normalized spectrum of the present invention has a plurality of absorption peaks;
图5是本发明光谱仪检测的光谱示意图；Fig. 5 is the spectrum schematic diagram that the spectrometer of the present invention detects;
图中，1-宽谱光源，2-光纤传感单元，21-螺旋芯光纤，22-无芯光纤，23-敏感金属薄膜，3-光谱仪，4-电脑。In the figure, 1-broad-spectrum light source, 2-optical fiber sensing unit, 21-spiral-core optical fiber, 22-coreless optical fiber, 23-sensitive metal film, 3-spectroscopy, 4-computer.
具体实施方式detailed description
下面结合附图和实施例对本发明的技术方案做进一步详细的说明。The technical solution of the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.
参照图1所示，本发明所述的分布式螺旋芯光纤表面等离子体共振传感器，包括宽谱光源1、光纤传感单元2和光谱仪3，宽谱光源1与光纤传感单元2的输入端连接，光纤传感单元2的输出端与光谱仪3连接，光谱仪3连接至电脑4。With reference to shown in Fig. 1, the distributed helical core optical fiber surface plasmon resonance sensor of the present invention comprises a wide-spectrum light source 1, an optical fiber sensing unit 2 and a spectrometer 3, and the input end of the wide-spectrum light source 1 and the optical fiber sensing unit 2 connection, the output end of the optical fiber sensing unit 2 is connected to the spectrometer 3 , and the spectrometer 3 is connected to the computer 4 .
参照图2所示，光纤传感单元2由一段螺旋芯光纤21和一段表面镀有敏感金属薄膜23的无芯光纤22构成的周期性结构组成，每个周期内敏感金属薄膜23的起点为螺旋芯光纤21和无芯光纤22的熔接点，敏感金属薄膜23的终点为无芯光纤22和螺旋芯光纤21的熔接点。Referring to Fig. 2, the optical fiber sensing unit 2 is composed of a periodical structure composed of a section of spiral core optical fiber 21 and a section of coreless optical fiber 22 coated with a sensitive metal film 23 on the surface. The starting point of the sensitive metal film 23 in each period is a helical The fusion point between the core fiber 21 and the coreless fiber 22 and the end point of the sensitive metal film 23 is the fusion point between the coreless fiber 22 and the spiral core fiber 21 .
无芯光纤22为去掉涂覆层的折射率一定的光纤。The coreless optical fiber 22 is an optical fiber with a constant refractive index without coating.
敏感金属薄膜23包括纳米金属薄膜、纳米金属氧化物薄膜、纳米合金薄膜及其他对湿度、温度、浓度、应力敏感的功能性及特异性材料薄膜。Sensitive metal films 23 include nano-metal films, nano-metal oxide films, nano-alloy films and other functional and specific material films that are sensitive to humidity, temperature, concentration and stress.
宽谱光源1为波长在400～1800nm范围内连续变化的无突变的连续谱白光激光光源。The wide-spectrum light source 1 is a continuous-spectrum white-light laser light source whose wavelength changes continuously within the range of 400-1800nm without sudden change.
光谱仪3为检测波长范围400～1800nm光强的光谱仪，检测灵敏度小于1nm。The spectrometer 3 is a spectrometer for detecting light intensity in a wavelength range of 400-1800nm, and the detection sensitivity is less than 1nm.
当光从宽谱光源1耦合进入螺旋芯光纤21时会激励起多个模式的光，但是不同模式的光的衰减系数不同。When light is coupled from the broadband light source 1 into the spiral core fiber 21, multiple modes of light will be excited, but the attenuation coefficients of different modes of light are different.
基模光的衰减系数用Marcuse模型表示：The attenuation coefficient of the fundamental mode light is expressed by the Marcuse model:
高阶模式的光的衰减系数用K.S.Kaufman模型表示:The attenuation coefficient of light in higher order modes is represented by the K.S.Kaufman model:
其中:a为纤芯半径，k为波矢量，V为归一化频率，R为曲率半径，为第二类Hankel函数，Kv是修正的Hankel函数。Ib可以表示为：Wherein: a is the fiber core radius, k is the wave vector, V is the normalized frequency, R is the radius of curvature, For the second kind of Hankel function, K v is the modified Hankel function. I b can be expressed as:
其中G可以表示为：where G can be expressed as:
G＝γR(n2k0)-2 (4)G=γR(n 2 k 0 ) -2 (4)
其中γ反映了导模倏逝场的衰减速度：where γ reflects the decay speed of the evanescent field of the guided mode:
k0为真空中的波矢量：k 0 is the wave vector in vacuum:
k0＝2π/λ (6)k 0 =2π/λ (6)
由上式可知，在螺旋芯光纤21中，高阶模式的光会快速损耗，但是基模光的能量几乎不会损耗。由于无芯光纤22的折射率大于外介质，因此无芯光纤22和外介质一起也构成了光密-光疏结构，也就是说无芯光纤22相当于一段多模光纤的纤芯，外介质相当于多模光纤的包层。当螺旋芯光纤21的基模光耦合进入无芯光纤时，会在无芯光纤22中激发起多个模式的光。其中，被激发的基模光直接通过无芯光纤22进入到下一段螺旋芯光纤21中，而高阶模式的光在无芯光纤22和外介质的交界面发生全反射并产生倏逝波，在无芯光纤22的包层外侧镀上敏感金属薄膜23会增大倏逝波的横向波矢，入射光中的P偏振光到达敏感金属薄膜23表面时部分穿透敏感金属薄膜23，当其水平方向波长与敏感金属薄膜23的等离子体波相匹配时，光的能量会因为表面等离子体共振现象的发生而急剧减弱。It can be known from the above formula that in the spiral core fiber 21, the light of the high-order mode will be rapidly lost, but the energy of the fundamental mode light will hardly be lost. Because the refractive index of the coreless fiber 22 is greater than that of the outer medium, the coreless fiber 22 and the outer medium together also form an optically denser-optical sparse structure, that is to say, the coreless fiber 22 is equivalent to the core of a section of multimode fiber, and the outer medium Equivalent to the cladding of a multimode fiber. When the fundamental mode light of the spiral core fiber 21 is coupled into the coreless fiber, multiple modes of light will be excited in the coreless fiber 22 . Among them, the excited fundamental mode light directly enters the next spiral core fiber 21 through the coreless fiber 22, while the light of the higher order mode is totally reflected at the interface between the coreless fiber 22 and the external medium and generates evanescent waves, Plating a sensitive metal film 23 on the outside of the cladding of the coreless optical fiber 22 will increase the transverse wave vector of the evanescent wave, and when the P-polarized light in the incident light reaches the surface of the sensitive metal film 23, it partially penetrates the sensitive metal film 23, and when it When the wavelength in the horizontal direction matches the plasma wave of the sensitive metal thin film 23, the energy of the light will be sharply weakened due to the phenomenon of surface plasmon resonance.
当环境介质的介电常数改变时，对应的共振波长也不同。因此，当上述传感结构处于一个大范围的单一环境中时，比如50％氢气50％氮气的环境中时，在光谱仪中测得的波谱只会有一个吸收峰，如图3所示。但是如果某一位置的气体浓度发生改变时，则会在光谱仪中检测到多个吸收峰，如图4所示，在观察到有多个吸收峰的情况下，使用对应的共振波长附近的光源作为入射光源，再用背向散射法可以测得发生表面等离子体共振的位置。When the dielectric constant of the environment medium changes, the corresponding resonance wavelength is also different. Therefore, when the above-mentioned sensing structure is in a single large-scale environment, such as an environment of 50% hydrogen and 50% nitrogen, the spectrum measured in the spectrometer will only have one absorption peak, as shown in FIG. 3 . However, if the gas concentration at a certain position changes, multiple absorption peaks will be detected in the spectrometer, as shown in Figure 4. When multiple absorption peaks are observed, use a light source near the corresponding resonance wavelength As the incident light source, the position where the surface plasmon resonance occurs can be measured by backscattering method.
背向散射法是将大功率的窄脉冲注射到被测光纤中，然后在同一端使用光时域反射仪检测光纤背向返回的散射光功率的方法，主要机理为瑞利散射。瑞利散射光的特征是它的光波长相同，光功率与该点的入射光功率成正比，所以测量沿光线返回的背向瑞利散射光功率就可以获得光沿光纤传输时的信息，从而可以测得光纤的衰减。具体对于本测试系统而言，如果不发生表面等离子体共振现象，则测得的反射光功率会随着时间的增长而缓慢减小。但是如果在某处发生表面等离子体共振现象，那么光传播到该处时背向散射光会急剧减小，通过这一现象可以测得发生表面等离子体共振现象的位置，检测结果示意图如图5所示。The backscattering method is to inject a high-power narrow pulse into the optical fiber under test, and then use an optical time domain reflectometer at the same end to detect the scattered light power returned by the optical fiber. The main mechanism is Rayleigh scattering. The characteristic of Rayleigh scattered light is that its light wavelength is the same, and the light power is proportional to the incident light power at this point, so the information of light transmission along the optical fiber can be obtained by measuring the back Rayleigh scattered light power along the light, so that The attenuation of the fiber can be measured. Specifically for this test system, if the surface plasmon resonance phenomenon does not occur, the measured reflected light power will slowly decrease with time. But if the surface plasmon resonance phenomenon occurs somewhere, the backscattered light will decrease sharply when the light propagates to this place. Through this phenomenon, the position where the surface plasmon resonance phenomenon occurs can be measured. The schematic diagram of the detection result is shown in Figure 5 shown.
显然，上述实施例仅仅是为清楚地说明本发明所作的举例，而并非是对本发明的实施方式的限定。对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式的变化或变动。这里无需也无法对所有的实施方式予以穷举。而这些属于本发明的精神所引伸出的显而易见的变化或变动仍处于本发明的保护范围之中。Apparently, the above-mentioned embodiments are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in different forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. And these obvious changes or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.
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