CN118603153A - A temperature and strain insensitive optical fiber vector torsion sensor - Google Patents
A temperature and strain insensitive optical fiber vector torsion sensor Download PDFInfo
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Abstract
本发明公开了一种温度和应变不敏感的光纤矢量扭转传感器,包括顺序连接的宽谱光源BBS、第一单模光纤SMF、保偏光纤PMF、少模光纤FMF、第二单模光纤SMF和光谱仪OSA,传感单元为SMF‑PMF‑FMF‑SMF熔接而成,传感单元两端分别连接宽谱光源BBS和光谱仪OSA构成传感系统,宽谱光源BBS发出光源进入第一单模光纤SMF,在保偏光纤PMF中形成第一个马赫曾德尔干涉仪MZI;传感单元SMF‑PMF‑FMF‑SMF中,少模光纤FMF与保偏光纤PMF的快轴方向错位拼接,错位量为12μm,将少模光纤FMF沿着PMF快轴方向错位拼接,在少模光纤FMF中形成第二个MZI;第二单模光纤SMF与光谱仪OSA连接。这种传感器结构紧凑、制作方便、可重复性高、对温度和应变不敏感,抗干扰能力强,易于集成。
The invention discloses a temperature and strain insensitive optical fiber vector torsion sensor, comprising a broadband light source BBS, a first single-mode optical fiber SMF, a polarization-maintaining optical fiber PMF, a few-mode optical fiber FMF, a second single-mode optical fiber SMF and a spectrometer OSA connected in sequence, a sensing unit formed by SMF-PMF-FMF-SMF fusion splicing, two ends of the sensing unit are respectively connected to the broadband light source BBS and the spectrometer OSA to form a sensing system, the broadband light source BBS emits a light source into the first single-mode optical fiber SMF, and a first Mach-Zehnder interferometer MZI is formed in the polarization-maintaining optical fiber PMF; in the sensing unit SMF-PMF-FMF-SMF, the fast axis direction of the few-mode optical fiber FMF and the polarization-maintaining optical fiber PMF are dislocated and spliced, and the dislocation amount is 12μm, and the few-mode optical fiber FMF is dislocated and spliced along the fast axis direction of the PMF to form a second MZI in the few-mode optical fiber FMF; the second single-mode optical fiber SMF is connected to the spectrometer OSA. The sensor has a compact structure, is easy to manufacture, has high repeatability, is insensitive to temperature and strain, has strong anti-interference ability, and is easy to integrate.
Description
技术领域Technical Field
本发明涉及光纤扭转传感器技术,尤其涉及基于级联马赫增德尔干涉的光纤扭转传感器,具体是一种温度和应变不敏感的光纤矢量扭转传感器。The invention relates to optical fiber torsion sensor technology, in particular to an optical fiber torsion sensor based on cascaded Mach-Zehnder interference, specifically to an optical fiber vector torsion sensor insensitive to temperature and strain.
背景技术Background Art
扭转是判断结构健康的重要指标。扭转传感器在土木工程、机械制造、生物机器人领域起着十分重要的作用。然而对于传统的电子扭转传感器,体积过大、结构复杂,成本高等缺点使得扭转测量成为技术难题。Torsion is an important indicator of structural health. Torsion sensors play a very important role in civil engineering, mechanical manufacturing, and biorobotics. However, traditional electronic torsion sensors have disadvantages such as large size, complex structure, and high cost, making torsion measurement a technical problem.
光纤传感器由于体积小,可绕性好,可以方便的埋入结构内部。基于光纤传感器研究逐渐成为国内外学者的热门研究方向。目前的光纤扭转传感器主要分为两种,一种是基于长周期光纤光栅和倾斜光纤布拉格光栅等栅型器件,但是制备仪器复杂昂贵,而且折射率调制型的传感器灵敏度较低;另一种是基于模间干涉型传感器。例如阮田甜公开了一种基于Sagnac环的扭转传感器,这种扭转传感器结构简单、制作方便,但是这种传感器容易受到温度的干扰;鲁平等人公开了在细芯光纤上拉锥来实现高灵敏无温度交叉敏感的光纤扭转器,但是这些拉锥结构会让光纤变得脆弱,抗机械强度低,限制了实际应用范围。Fiber optic sensors are small in size and easy to be twisted, so they can be easily buried inside structures. Research based on fiber optic sensors has gradually become a hot research direction for scholars at home and abroad. At present, there are two main types of fiber optic torsion sensors. One is based on grating devices such as long-period fiber gratings and tilted fiber Bragg gratings, but the preparation equipment is complicated and expensive, and the refractive index modulation type sensor has low sensitivity; the other is based on inter-mode interference type sensors. For example, Ruan Tiantian disclosed a torsion sensor based on Sagnac rings. This torsion sensor has a simple structure and is easy to make, but this sensor is easily affected by temperature; Lu Ping et al. disclosed a high-sensitivity fiber optic torsion device with no temperature cross-sensitivity by tapering on a thin-core optical fiber, but these taper structures make the optical fiber fragile and have low mechanical strength, which limits the scope of practical application.
因此,研究并提供一种结构简单、制作方便、可重复性高、对温度和应变不敏感,抗干扰能力强的扭转传感器具有较高的应用价值。Therefore, it is of great application value to study and provide a torsion sensor which has a simple structure, is easy to manufacture, has high repeatability, is insensitive to temperature and strain, and has strong anti-interference ability.
发明内容Summary of the invention
本发明的目的是针对现有技术的不足,而提供一种温度和应变不敏感的光纤矢量扭转传感器。这种传感器结构紧凑、制作方便、可重复性高、对温度和应变不敏感,抗干扰能力强,易于集成。The purpose of the present invention is to provide a temperature and strain insensitive optical fiber vector torsion sensor in view of the shortcomings of the prior art. The sensor has a compact structure, is easy to manufacture, has high repeatability, is insensitive to temperature and strain, has strong anti-interference ability, and is easy to integrate.
实现本发明目的的技术方案是:The technical solution for achieving the purpose of the present invention is:
一种温度和应变不敏感的光纤矢量扭转传感器, 包括顺序连接的宽谱光源BBS(broadband source,简称BBS)、第一单模光纤SMF(single-mode fiber,简称SMF)、保偏光纤PMF(polarization maintaining optical fiber, 简称PMF)、少模光纤FMF(few-modefiber,简称FMF)、第二单模光纤SMF和光谱仪OSA(Optical Spectrum Analyzer,简称OSA),传感单元为SMF-PMF-FMF-SMF熔接而成,传感单元两端分别连接宽谱光源BBS和光谱仪OSA构成传感系统,宽谱光源BBS发出光源进入第一单模光纤SMF,在保偏光纤PMF中形成第一个马赫曾德尔干涉仪MZI(Mach-Zehnder Interferometer,简称MZI);传感单元SMF-PMF-FMF-SMF中,少模光纤FMF与保偏光纤PMF的快轴方向错位拼接,错位量为12μm,将少模光纤FMF沿着PMF快轴方向错位拼接,在少模光纤FMF中形成第二个MZI;第二单模光纤SMF与光谱仪OSA连接。A temperature and strain insensitive optical fiber vector torsion sensor comprises a broadband source BBS (BBS), a first single-mode fiber SMF (SMF), a polarization maintaining optical fiber PMF (PMF), a few-mode fiber FMF (FMF), a second single-mode optical fiber SMF and an optical spectrum analyzer OSA (OSA) connected in sequence, wherein the sensing unit is formed by SMF-PMF-FMF-SMF fusion splicing, and the two ends of the sensing unit are respectively connected to the broadband source BBS and the spectrometer OSA to form a sensing system, wherein the broadband source BBS emits a light source into the first single-mode optical fiber SMF, and forms a first Mach-Zehnder interferometer MZI (Mach-Zehnder Interferometer, MZI for short); in the sensing unit SMF-PMF-FMF-SMF, the few-mode fiber FMF and the polarization-maintaining fiber PMF are spliced in the fast axis direction with a misalignment of 12 μm. The few-mode fiber FMF is spliced in the fast axis direction of the PMF to form a second MZI in the few-mode fiber FMF; the second single-mode fiber SMF is connected to the spectrometer OSA.
所述宽谱光源BBS从传感单元SMF-PMF-FMF-SMF的第一单模光纤SMF入射,第一单模光纤SMF纤芯直径为9μm、保偏光纤PMF纤芯直径为6.5μm,光经过保偏光纤PMF时分成两部分、分别沿着保偏光纤PMF的纤芯和包层中传输,形成第一个MZI。The broadband light source BBS is incident from the first single-mode optical fiber SMF of the sensing unit SMF-PMF-FMF-SMF. The core diameter of the first single-mode optical fiber SMF is 9 μm, and the core diameter of the polarization-maintaining optical fiber PMF is 6.5 μm. When the light passes through the polarization-maintaining optical fiber PMF, it is divided into two parts and is transmitted along the core and cladding of the polarization-maintaining optical fiber PMF respectively, forming the first MZI.
保偏光纤PMF与少模光纤FMF错位拼接,从BBS发出的宽带光源经过保偏光纤FMF时被分成两部分、分别沿着少模光纤FMF的纤芯和包层向前传输,汇聚到第二单模光纤SMF纤芯,形成第二个MZI,最后光谱信息被光谱仪OSA收集。The polarization-maintaining fiber PMF and the few-mode fiber FMF are staggered and spliced. The broadband light source emitted from the BBS is divided into two parts when passing through the polarization-maintaining fiber FMF, and is transmitted forward along the core and cladding of the few-mode fiber FMF respectively, and converges to the core of the second single-mode fiber SMF to form the second MZI. Finally, the spectral information is collected by the spectrometer OSA.
在保偏光纤PMF和少模光纤FMF产生的两个MZIs的自由谱宽分别表示为:The free spectral widths of the two MZIs generated in the polarization-maintaining fiber PMF and the few-mode fiber FMF are expressed as:
, (i为输入快轴或慢轴偏振模式), , (i is the input fast axis or slow axis polarization mode),
其中,λ表示波长,△np,i和△nf分别表示在保偏光纤PMF和少模光纤FMF中的有效折射率差,Lp和Lf分别表示在保偏光纤PMF和少模光纤FMF中的干涉长度,Where, λ represents the wavelength, △n p,i and △n f represent the effective refractive index difference in the polarization-maintaining fiber PMF and the few-mode fiber FMF, Lp and Lf represent the interference length in the polarization-maintaining fiber PMF and the few-mode fiber FMF, respectively.
则两个MZIs形成的包络的自由谱宽表示为:Then the free spectral width of the envelope formed by the two MZIs is expressed as:
。 .
当传感器进行扭转测量时,通过监测SMF-PMF-FMF-SMF传感单元中的包络峰的波长变化,即可实现扭转角度测量。When the sensor performs torsion measurement, the torsion angle measurement can be achieved by monitoring the wavelength change of the envelope peak in the SMF-PMF-FMF-SMF sensing unit.
通过调控SMF-PMF-FMF-SMF结构中PMF和FMF长度可以获得更高质量的包络,其中,优化后PMF和FMF长度分别为LPMF=3cm,LFMF=3cm。A higher quality envelope can be obtained by adjusting the lengths of PMF and FMF in the SMF-PMF-FMF-SMF structure, where the optimized lengths of PMF and FMF are L PMF =3cm and L FMF =3cm, respectively.
由于扭转过程中会导致传感单元结构发生椭圆双折射,因此传感单元结构在往不同方向扭转时会产生差异,通过检测拟合的包络的波长飘移方向,可以判别传感器的扭转方向,传感器实现矢量扭转测量。Since the torsion process will cause elliptical birefringence in the sensor unit structure, the sensor unit structure will produce differences when twisted in different directions. By detecting the wavelength drift direction of the fitted envelope, the torsion direction of the sensor can be determined, and the sensor can realize vector torsion measurement.
这种传感器结构紧凑、制作方便、可重复性高、对温度和应变不敏感,抗干扰能力强,易于集成。This sensor has a compact structure, is easy to manufacture, has high repeatability, is insensitive to temperature and strain, has strong anti-interference ability, and is easy to integrate.
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
图1为实施例中传感器的系统结构示意图;FIG1 is a schematic diagram of the system structure of a sensor in an embodiment;
图2为实施例中PMF与FMF错位熔接截面图示意图;FIG2 is a schematic diagram of a cross-sectional view of the offset welding of PMF and FMF in an embodiment;
图3为实施例中传感结构光谱及拟合包络峰示意图;FIG3 is a schematic diagram of the sensing structure spectrum and the fitted envelope peak in an embodiment;
图4为实施例中级联MZI包络峰示意图,其中图(a)为级联MZI包络峰顺时针包络峰的波长变化示意图,其中图(b)为级联MZI包络峰逆时针包络峰的波长变化示意图。4 is a schematic diagram of the cascaded MZI envelope peak in an embodiment, wherein FIG (a) is a schematic diagram of the wavelength change of the cascaded MZI envelope peak clockwise, and FIG (b) is a schematic diagram of the wavelength change of the cascaded MZI envelope peak counterclockwise.
图中,1. 宽带光源 2. 第一单模光纤 3. 保偏光纤 4. 少模光纤 5. 第二单模光纤 6. 光谱仪。In the figure, 1. Broadband light source 2. First single-mode optical fiber 3. Polarization-maintaining optical fiber 4. Few-mode optical fiber 5. Second single-mode optical fiber 6. Spectrometer.
具体实施方式DETAILED DESCRIPTION
下面结合附图和实施例对本发明的内容作进一步的阐述,但不是对本发明的限定。The content of the present invention is further described below in conjunction with the drawings and embodiments, but the present invention is not limited thereto.
实施例:Example:
参照图1,一种温度和应变不敏感的光纤矢量扭转传感器, 包括顺序连接的宽谱光源BBS、第一单模光纤SMF、保偏光纤PMF、少模光纤FMF、第二单模光纤SMF和光谱仪OSA,宽谱光源BBS发出光源进入第一单模光纤SMF,在保偏光纤PMF中形成第一个马赫曾德而干涉仪MZI;将少模光纤FMF沿着PMF快轴方向错位12μm拼接,在少模光纤FMF中形成第二个MZI;第二单模光纤SMF与光谱仪OSA连接,传感单元为SMF-PMF-FMF-SMF熔接而成,传感单元两端分别连接宽谱光源BBS和光谱仪OSA构成传感系统。1 , a temperature- and strain-insensitive optical fiber vector torsion sensor includes a broadband light source BBS, a first single-mode optical fiber SMF, a polarization-maintaining optical fiber PMF, a few-mode optical fiber FMF, a second single-mode optical fiber SMF and a spectrometer OSA connected in sequence, wherein the broadband light source BBS emits a light source into the first single-mode optical fiber SMF, and forms a first Mach-Zehnder interferometer MZI in the polarization-maintaining optical fiber PMF; the few-mode optical fiber FMF is spliced along the fast axis direction of the PMF with a 12 μm offset, and a second MZI is formed in the few-mode optical fiber FMF; the second single-mode optical fiber SMF is connected to the spectrometer OSA, and the sensing unit is formed by SMF-PMF-FMF-SMF fusion splicing, and both ends of the sensing unit are respectively connected to the broadband light source BBS and the spectrometer OSA to form a sensing system.
所述传感单元SMF-PMF-FMF-SMF中,少模光纤FMF与保偏光纤PMF的快轴方向错位拼接,其中,错位量为12μm,如图2所示。In the sensing unit SMF-PMF-FMF-SMF, the fast axis directions of the few-mode fiber FMF and the polarization-maintaining fiber PMF are staggered and spliced, wherein the amount of stagger is 12 μm, as shown in FIG. 2 .
所述宽谱光源BBS从传感单元SMF-PMF-FMF-SMF的第一单模光纤SMF入射,第一单模光纤SMF纤芯直径为9μm、保偏光纤PMF纤芯直径为6.5μm,由于模场直径不匹配,光经过保偏光纤PMF时分成两部分、分别沿着保偏光纤PMF的纤芯和包层中传输,形成第一个MZI。The broadband light source BBS is incident from the first single-mode optical fiber SMF of the sensing unit SMF-PMF-FMF-SMF. The core diameter of the first single-mode optical fiber SMF is 9 μm, and the core diameter of the polarization-maintaining optical fiber PMF is 6.5 μm. Due to the mismatch of mode field diameters, the light is divided into two parts when passing through the polarization-maintaining optical fiber PMF, and is transmitted along the core and cladding of the polarization-maintaining optical fiber PMF respectively, to form the first MZI.
所述保偏光纤PMF与少模光纤FMF错位拼接,因此从BBS发射出来的宽谱光源经过保偏光纤FMF时被分成两部分、分别沿着少模光纤FMF的纤芯和包层向前传输,汇聚到第二单模光纤SMF纤芯,形成第二个MZI,最后光谱信息被光谱仪OSA收集。The polarization-maintaining fiber PMF and the few-mode fiber FMF are staggered and spliced, so the wide-spectrum light source emitted from the BBS is divided into two parts when passing through the polarization-maintaining fiber FMF, and is transmitted forward along the core and cladding of the few-mode fiber FMF respectively, and converges to the core of the second single-mode fiber SMF to form a second MZI, and finally the spectral information is collected by the spectrometer OSA.
在保偏光纤PMF和少模光纤FMF产生的两个MZIs的自由谱宽分别表示为:The free spectral widths of the two MZIs generated in the polarization-maintaining fiber PMF and the few-mode fiber FMF are expressed as:
, (i为输入快轴或慢轴偏振模式), , (i is the input fast axis or slow axis polarization mode),
其中,λ表示波长,△np,i和△nf分别表示在保偏光纤PMF和少模光纤FMF中的有效折射率差,Lp和Lf分别表示在保偏光纤PMF和少模光纤FMF中的干涉长度,Where, λ represents the wavelength, △n p,i and △n f represent the effective refractive index difference in the polarization-maintaining fiber PMF and the few-mode fiber FMF, Lp and Lf represent the interference length in the polarization-maintaining fiber PMF and the few-mode fiber FMF, respectively.
则两个MZIs形成的包络的自由谱宽表示为:Then the free spectral width of the envelope formed by the two MZIs is expressed as:
。 .
当传感器进行扭转测量时,通过监测SMF-PMF-FMF-SMF传感单元中的包络峰的波长变化,即可实现扭转角度测量。When the sensor performs torsion measurement, the torsion angle measurement can be achieved by monitoring the wavelength change of the envelope peak in the SMF-PMF-FMF-SMF sensing unit.
通过调控SMF-PMF-FMF-SMF结构中的PMF和FMF长度可以获得更高质量的包络,其中,本例中PMF和FMF的长度分别为LPMF=3cm,LFMF=3cm,拟合包络图像如图3所示,由于扭转过程中会导致传感单元结构发生椭圆双折射,因此传感单元结构在往不同方向扭转时会产生差异,如图4所示,通过检测拟合的包络的波长飘移方向,可以判别传感器的扭转方向,传感器实现矢量扭转测量。By adjusting the lengths of PMF and FMF in the SMF-PMF-FMF-SMF structure, a higher quality envelope can be obtained. In this example, the lengths of PMF and FMF are L PMF =3cm and L FMF =3cm respectively. The fitted envelope image is shown in FIG3 . Since the sensor unit structure will cause elliptical birefringence during the torsion process, the sensor unit structure will produce differences when twisted in different directions, as shown in FIG4 . By detecting the wavelength drift direction of the fitted envelope, the torsion direction of the sensor can be determined, and the sensor realizes vector torsion measurement.
本例中沿着PMF快轴方向12μm与FMF错位拼接,其余光纤是对芯熔接,工作时,宽谱光源1发出的光经过第一单模光纤,在PMF中被分成两束光分别沿着PMF3的纤芯和包层传输,形成第一个MZI;经过错位点后,光分别沿着FMF4的纤芯和包层传输,汇聚在第二单模光纤5中,形成第二个MZI;当传感器发生扭转时,由于PMF-FMF扭曲诱导椭圆双折射导致偏振态(SOP)演变,这种椭圆上折射改变了纤芯模式和包层模式的SOP,导致两者之间的有效折射率发生变化。从而使得拟合出的倾角包络波长偏移方向产生差异,允许传感器来实现扭转测量和区分扭转方向。In this example, the PMF is spliced with the FMF at 12μm along the fast axis direction, and the rest of the optical fibers are core-fused. When working, the light emitted by the broadband light source 1 passes through the first single-mode optical fiber, and is divided into two beams in the PMF, which are transmitted along the core and cladding of PMF3 respectively, forming the first MZI; after passing the offset point, the light is transmitted along the core and cladding of FMF4 respectively, and converges in the second single-mode optical fiber 5, forming the second MZI; when the sensor is twisted, the polarization state (SOP) evolves due to the elliptical birefringence induced by the PMF-FMF twist. This elliptical refraction changes the SOP of the core mode and the cladding mode, causing the effective refractive index between the two to change. As a result, the fitted tilt envelope wavelength offset direction is different, allowing the sensor to achieve torsion measurement and distinguish the torsion direction.
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