基于模式竞争效应的差分型四芯光纤SPR传感机理研究

Multi-core fiber SPR(Surface Plasmon Resonance) sensor has the advantages of low mode noise, easy to realize multichannel detection, compatibility with high sensitivity and wide measurement range. However, due to its working band is not the low loss band of optical fiber communication, and it works in wavelength interrogation mode, which limits its remote sensing ability, makes it unable to take into account both sensitivity and resolution, and makes it difficult to further improve sensitivity. In this proposal, firstly, four-core fiber-optic SPR sensor is fabricated utilizing fiber grinding and vacuum coating technology, and the response characteristics of SPR in 1.5 μm optical fiber communication band are adjusted. Differential intensity demodulation is used to avoid the mutual restriction of sensitivity and resolution, and to enable the sensor to acquire remote sensing capability. Secondly, by using the dual-channel four-core fiber probe as the two cavity mirrors of dual-wavelength fiber laser, the differential modulation of reflectance by the change of refractive index to be measured is utilized to adjust the intra-cavity loss, which triggers the intra-cavity mode competition effect, and then the influence rules of refractive index change on mode competition effect are revealed, so that a new mechanism of sensitivity enhancement is constructed to promote the progress of multi-core optical fiber SPR sensing technology.

多芯光纤SPR（Surface Plasmon Resonance）传感器具有低模式噪声、易实现多通道探测、可兼顾灵敏度和量程等优势，但因工作波段非光纤通信的低损波段且工作于波长解调模式，限制了其远程传感能力，使其无法兼顾灵敏度和分辨率，难以进一步提高灵敏度。本项目首先拟利用光纤研磨和真空镀膜技术，制备四芯光纤SPR传感器、调控1.5微米光纤通信波段的SPR响应特性，采用差分强度解调方法避免灵敏度和分辨率的相互制约，并使传感器获得遥测能力；其次，拟通过将双通道四芯光纤探头作为双波长光纤激光器的两个腔反射镜，利用待测折射率变化对反射率的差分调制作用，调控腔内损耗，引发腔内模式竞争效应，揭示待测折射率变化对模式竞争效应的影响规律，构建灵敏度增强的新机制，促进多芯光纤SPR传感的技术进步。

为了使多芯光纤SPR传感器获得远程传感能力并兼顾灵敏度和分辨率，本项目利用光纤研磨和真空镀膜技术，制备了光纤-棱镜结合型SPR传感器、四芯光纤CPWR传感器，在C波段采用差分强度解调方法避免了灵敏度和分辨率相互制约的问题，并使传感器获得了遥测能力。为了进一步增强灵敏度，组建了带有ASE光外部注入的双波长环形腔光纤激光器，将四芯光纤探头融入其中作为调节腔内损耗的元件，利用待测折射率变化对反射率的差分调制作用，调控腔内损耗，引发了腔内模式竞争效应，揭示了待测折射率变化对模式竞争效应的影响规律。由此，构建了灵敏度增强的新机制。与传统差分强度解调方法相比，灵敏度提升了10倍，为强度解调型SPR传感器提供了新的灵敏度增强途径。