Brillouin Gain Spectrum And Temperature Sensitization Of Micro-nano Fiber

With the continuous development of laser technology,the research scope of optical fiber sensing technology has been continuously expanded.New sensing mechanisms and new fibers have gradually become one of the main directions of optical fiber sensing research.The diameter of micro-nano fiber is in the order of hundreds of nanometers to micrometers.This order of size brings unique light and acoustics characteristics to it,and also leads to the photoacoustic interaction in the micro-nano fiber,such as stimulated Brillouin scattering(SBS)provides a great research space.At the same time,due to the inherent material properties of Si O₂,the temperature sensitivity of the Brillouin gain spectrum of Si O₂ fibers,including micro-nano fibers,is often limited to the order of1MHz/?.In view of the above problems,this paper studies the Brillouin gain spectrum characteristics of micro-nano fibers,and proposes a solution to improve its temperature sensitivity,and conducts theoretical simulation and experimental verification on it.First of all,starting from the process of SBS,the SBS effect in the optical fiber is theoretically studied through the coupled wave equation,and the connection of Brillouin scattering in the optical fiber and temperature sensing is explored,and the SBS effect used to excite and measure the optical fiber is described.Technical method.This provides a theoretical basis and research methods for subsequent simulation calculations and theoretical research.Secondly,the unique stimulated Brillouin scattering characteristics of the micro-nano fiber are simulated and verified by experiments.The Brillouin gain spectrum characteristics of micro-nano fibers of different structures and materials are simulated to clarify the main physical effects and their specific effects.Using phase shift keying Brillouin optical correlation domain analysis technology to achieve fixed-point local excitation of SBS in a micro-nano fiber section with a length of about 1 cm and achieve gain spectrum measurement.The simulation results of the experiment have a good match,indicating that the measurement of the SBS gain spectrum can be achieved Effectively used to characterize the diameter and surface morphology of micro-nano fibers.Finally,in order to realize the temperature sensitivity enhancement of the SBS gain spectrum in the micro-nano fiber,a sensor structure combining PMMA material and the micro-nano fiber is proposed.According to the thermal expansion mismatch of PMMA and Si O₂ and the strain concentration of the micro-nano fiber section when the fiber is stretched as a whole,the temperature sensitivity of the Brillouin frequency shift of the micro-nano fiber is realized,and the temperature sensitivity of 19.622MHz/?in the range of 17 to 30?is obtained.Which is an order of magnitude higher than the existing Brillouin temperature sensing technology.