Bichler Anthony, Lecler Sylvain, Serio Bruno, Fischer Sylvain, Pfeiffer Pierre
InESS-Photonic, Strasbourg University, CNRS, 2012, BP 10413, Illkirch F-67412, France.
J Opt Soc Am A Opt Image Sci Vis. 2012 Nov 1;29(11):2386-93. doi: 10.1364/JOSAA.29.002386.
A step index multimode optical fiber with a perturbation on a micrometer scale, inducing a periodic deformation of the fiber section along its propagation axis, is theoretically investigated. The studied microperturbation is mechanically achieved using two microstructured jaws squeezing the straight fiber. As opposed to optical fiber microbend sensors, the optical axis of the proposed transducer is not bended; only the optical fiber section is deformed. Further, the strain applied on the fiber produces a periodical elliptical modification of the core and a modulation of the index of refraction. As a consequence of the micrometer scale perturbation period, the resulting mode coupling occurs directly between guided and radiated modes. To simulate the transmission induced by these kinds of perturbations, simplified models considering only total mode couplings are often used. In order to investigate the range of validity of this approximation, results are compared to the electromagnetic mode couplings rigorously computed for the first time, to our knowledge, with a large multimode fiber (more than 6000 linear polarized modes) using the Marcuse model. In addition, in order to have a more complete modeling of the proposed transducer, the anisotropic elasto-optic effects in the stressed multimode fiber are considered. In this way, the transmission of the microperturbed optical fiber transmission and, therefore, the behavior of the transducer are physically explained and its applications as a future stretching sensor are discussed.
对一种具有微米级微扰的阶跃折射率多模光纤进行了理论研究，该微扰会导致光纤截面沿其传播轴产生周期性变形。所研究的微扰是通过使用两个微结构夹爪挤压直光纤来机械实现的。与光纤微弯传感器不同，所提出的换能器的光轴不弯曲；只有光纤截面发生变形。此外，施加在光纤上的应变会使纤芯产生周期性的椭圆变化以及折射率的调制。由于微扰周期为微米级，所产生的模式耦合直接发生在导模和辐射模之间。为了模拟由这类微扰引起的传输，通常使用仅考虑全模式耦合的简化模型。为了研究这种近似的有效性范围，将结果与据我们所知首次使用Marcuse模型对大尺寸多模光纤（超过6000个线偏振模）严格计算的电磁模式耦合结果进行了比较。此外，为了对所提出的换能器进行更完整的建模，考虑了受应力多模光纤中的各向异性弹光效应。通过这种方式，从物理角度解释了微扰光纤的传输以及换能器的行为，并讨论了其作为未来拉伸传感器的应用。
