Study And Modeling Of Magnetic Fluid Transmittance Properties In Optical Fiber By Applying Magnetic Field

Magnetic fluid,which is composed of nanoscale paramagnetic particles by surfactant dispersed in some kind of carrier liquid, is a kind of stable colloidal solution.lt has magnetic properties of solid and fluidity of liquid. Under the effect of magnetic field,the magnetic fluid show the rich microscopic structure.Thus it show a variety of optical properties which can be applied in the field of optics and optical fiber sensing.Therefore,it is very significant to study the light transmission characteristics of magnetic fluid under the effect of external magnetic field.Though the study of the light transmission characteristics of magnetic fluid under the effect of external magnetic field has been done a lot for many years, its mechanism and laws is not very clear, and the studies usually focused on the magnetic fluid in the sample box. This paper designs a new kind of research method. The sample will be got by placing magnetic fluid in optical fibers. And then the light transmittance characteristics of magnetic fluid in optical fibers will be studied in this paper. The research work and achievements include the following components:1. The preparation of magnetic fluid optical fiber sample and the design of the external magnetic fied、the derivation and numerical calculation of the magnetic field distribution. As to the special structure of fiber,the device of preparing the magnetic fluid sample is designed. According to the experimental requirements, the device of the external magnetic field is designed too.Then we establish the theoretical models and carry out numerical calculation for the distribution of uniform magnetic field and gradient magnetic field to verify the rationality of the models.2. The research of the light transmittance characteristics of magnetic fluid in optical fiber under the uniform magnetic field.Put the sample into the environment of uniform magnetic field and study the influence of magnetic field strength and magnetic field direction on the light transmittance characteristics of magnetic fluid in optical fiber and implement curve fitting according to the light transmittance of magnetic fluid with the changes of magnetic field strength3. The research of the light transmittance characteristics of magnetic fluid in optical fiber under the gradient magnetic field.Under the effect of gradient magnetic field, we study the light transmittance of the magnetic fluid.According to the experimental results,the Langevin function and fluid theory and the Beer-Lambert law, we establish a theoretical model of the optical power transmission attenuation and the local density of nanoparticles and carry out a numerical analysis to verify the rationality of the model.The experimental results show that magnetic fluid in optical fiber under the effect of magnetic field has the light transmittance modulation effects obviously.In addition, the light transmittance characteristics of magnetic fluid in optical fiber under the uniform magnetic field and the gradient magnetic field is not the same. Analysis shows that the magnetic nanoparticles mainly form chains and agglomeration under uniform magnetic field.However, under gradient magnetic field,the re-distribution of the density of the nanoparticles in optical fiber leads to different light transmittance characteristics.And the numerical results confirm this. The research of the change of light transmittance characteristics of the magnetic fluid in the optic fiber under the external magnetic field is hoped to be used in optical switch, optical modulator, optical attenuator, magnetic field sensor, current sensor and so on.