Investigation For The Sensing Characteristics And Fabrication Of Helical Sampled Bragg Fiber Grating

Fiber Bragg gratings are key components in modern communication and sensing areas.For example,they have been extensively used for fast-speed optical filtering and optical communications.They also be used for new double-loop desensitization FBG strain sensor.The sensor can acurately realize online monitor in real time.For further enrich the application of FBG,Some application requires to introduce extra structure to FBG.One possible structure is sampled fiber Bragg grating.It can be fabricated by overlaying a sampling function on FBG,which results in a re-modulation for the core effective refractive index of the fiber.At present,sampled fiber Bragg gratings have been widely used in dispersion compensators and multiply sensors due to their excellent wavelength selectivity and multichannel characteristic.This paper focuses on fabrication and sensing characteristic of sampled fiber Bragg gratings.We propose a novel type of sampled fiber Bragg gratings to overcome the drawback of the gratings with the conventional fabrication methodologies,such as CO₂ laser writing,amplitude mask and femtosecond laser inscription technique.Our structure is formed by overlaying a FBG on helical twisted structure.The helical twisted structure is fabricated by special fiber splicer?Fujikura FSM-100P+?.The formed fiber core is helical and the clad is cylinder.Then the FBG is written by UV side illumination and the phase mask technique.The sampled period can be directly changed by adjusting the twist rate of the helical structure.The advantages of such a novel sampled fiber Bragg grating lie on their high controllability,high repeatability,and low fabrication cost.The main contents of this paper include:?1?A helical fiber-based sampled fiber Bragg grating is proposed and fabricated by electrode discharge method and the UV writing technique.It is fabricated by using a standard single mode fiber?Corning,SMF-28?.The characteristic of the spectrum are studied.The phenomena in experiment are summarized and discussed.We also investigate the influence of the parameters on the characteristic of spectrum by controling variable.The structure of novel sampled fiber Bragg gratings compare to past congener is original,and its cost is low,just inscribing FBG.?2?The sensing characteristics of the sampled fiber Bragg grating are investigated,and further propose the feasibility for simultaneously dual-parameters sensing.Both the helical fiber and the FBG responses to temperature,mechanical torsion,and axial strain are experimentally analyzed.The achieved temperature sensitivities are 60.51pm/°C and 10.12pm/°C,respecgtively.The achieved mechanical torsion sensitivities are 64.64nm·mm·rad^-11 and 0.00nm·mm·rad^-1,respectively.The achieved strain sensitivities are 0.316pm/??and 0.046pm/??,respectively.Analysis shows that this structure can be explored as a simultaneous sensor for detection of two parameters,such as temperature and mechanical torsion rate,or temperature and axial strain.The results show potential applications in the fields of fiber laser,sensors and communications.