Research On Characteristics And Application Of Hole-Assisted Few Mode Fiber

Optical fiber,as a light transmission tool,has expanded from traditional optical communication to various fields of the industry due to its low loss,lightweight,strong antiinterference ability,and low cost,and has played an irreplaceable function in some high-end industries.At present,a series of optical fiber devices are derived from microstructured fibers for their self-generating properties.Optical fiber sensors based on air-hole-assisted optical fibers have a higher sensitivity to sensing characteristics such as high temperature,high pressure,and two-dimensional bending.This topic mainly studies the influence of the number and location of air holes on the fiber transmission characteristics,as well as the preparation method of long-period fiber gratings based on three-hole fiber,and the measurement of temperature,bending,and refractive index were investigated.Aiming at the coupling mechanism and sensing characteristics of the hole-assisted few-mode fiber,we have made a series of investigations from the theoretical and experimental aspects:1.Use simulation software such as Matlab and Comsol to construct a hole-assisted fewmode fiber model and study its light guiding mechanism.At the same time,the effect of the number and spacing of air holes in the hole-assisted fiber on its transmission characteristics is analyzed,including mode field diameter,electric field distribution,effective refractive index,etc.2.Set up a pressure-assisted combined with a carbon dioxide laser device,which is used to write fiber grating.This device realizes the preparation of periodically deformed fiber gratings by controlling an external air pressure pump.3.A pressure source is used to inflate the inside of the hole-assisted optical fiber while the laser light was emitted.The convention single-mode fiber is spliced at both ends to form a long-period expanded optical fiber grating.The curvature,temperature,torsion and strain are measured experimentally.4.The pressure source is used to pump the hole to help the fiber to make the fiber air hole in a negative pressure state.The laser light is used to prepare the collapsed fiber.The ordinary single-mode fiber is spliced at both ends to form a collapsed long-period fiber grating.Meanwhile,curvature,refractive index,temperature,torsion,and strain are measured experimentally.The paper mainly conducts the theoretical analysis of the home-made hole-assisted fewmode fiber.At the same time,the collapsed long-period fiber grating and the inflated longperiod fiber grating based on the three-hole few-mode fiber are fabricated.The response of environmental parameters verifies that this type of grating can be used as different types of sensors and is widely used in the fields of optical fiber sensing and optical fiber communication.