Font Size: a A A

All-optical Fiber Microstructure Sensors Fabricated By Femtosecond Laser Direct Writing Technique

Posted on:2019-01-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:P C ChenFull Text:PDF
GTID:1368330545490409Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
All-optical fiber sensors are widely used in defense military,aerospace,rail transit,energy security,environmental monitoring,industrial production,medical monitoring,perimeter security and other fields because they have the advantages of microminiaturization,lighter weight,anti-electromagnetic interference,chemical resistance,high sensitivity,good remote control,suitable for harsh conditions,constitute a distributed optical fiber sensor network,real-time online in-situ detection,etc.Recently,due to the characteristics of high processing efficiency,small thermal effect,high processing precision and real three-dimensional structure micromachining,etc.,the emerging femtosecond laser direct writing technology has great application prospects in the field of optical fiber microstructure sensor fabrication.Therefore,the research on femtosecond laser direct writing technology for fabrication of all-optical fiber sensing devices not only has high scientific research value but also has significant social and economic benefits and national defense security significance.It has rapidly developed into one of the leading frontiers of multidisciplinary intersecting.This thesis focuses on the development of new types of all-optical fiber microstructure sensors based on the femtosecond laser direct writing technology.The main research contents and innovations are as follows:(1)A method of inducing an in-fiber refractive index-modified dot(RIMD)in single mode fiber by femtosecond laser direct writing technique was proposed,thereby we fabricated a low interference fringe contrast fiber Fabry-Perot interferometer(FPI).When the FPI is used for refractive index(RI)measurement,its sensitivity was found to be extremely high.Through subsequent theoretical analysis and experimental verification,it was found for the first time that there was two extremely sensitive zones for RI measurement.In addition,this all-optical fiber FPI can overcome temperature crosstalk issues.(2)A composite FPI fabricated by femtosecond laser micromachining can achieve high RI sensitivity and large dynamic range simultaneously.The basic principle of for the measurement with high sensitivity and large dynamic range the composite FPI was analyzed in detail.The influence of the parameters of the composite FPI on the dynamic range was explored through theoretical calculations,and we found that the range of the ultra-sensitive zones can be considerably adjusted to match the end requirements.The experimental results are consistent with the theoretical calculations.(3)A high interference fringe contrast all-optical fiber FPI probe for high-temperature measurement was proposed.The theoretical calculations found that the interference fringe contrast of the all-optical fiber FPI based on the RIMD induced by femtosecond laser could be easily adjusted.By optimizing the experimental parameters,a series of high interference fringe contrast(>20dB)fiber FPIs with different cavity lengths were obtained by femtosecond laser direct writing technique.We further studied and discussed the hightemperature sensing characteristics of the fabricated FPI,and found the FPI has a very high linearity to the temperature response.(4)A new type of in-fiber-core high-quality all-optical fiber Mach-Zehnder interferometer(MZI)was fabricated by femtosecond laser direct writing technique in single mode fiber.The fabrication conditions and the fabrication process of the MZI structure were described in detail.The performance and the working principle of the MZI were deeply studied through the experimental measurement results,theoretical analysis and simulation.The response of this MZI structure to some basic physical measurands(RI,temperature and strain)was further investigated by experiments and it is found that the MZI was almost insensitive or has a very low sensitivity to these physical measurands.Therefore,the proposed MZI has great potential in the field of optical fiber laser and all-optical signal processing.(5)The vector bend sensing characteristics of the high-quality in-fiber-core MZI fabricated by femtosecond laser was studied.The in-fiber-core MZI can maintain a linear response in a wide curvature range and can recognize directions.The bending response characteristic of the MZI was analyzed and explained through a theoretical model.Moreover,the proposed structure was immune to surrounding RI and has very small temperature and strain crosstalk.(6)A novel assembly-free multi-mode interferometer(MMI)was fabricated by femtosecond laser direct writing technique in single mode fiber.The fabrication conditions and process of the MMI structure were described in detail.The performance and working principle of the proposed MMI were studied through the experimental measurement,theoretical analysis and simulation.The response of the MMI structure to surrounding RI was further studied by experiments and simulations.
Keywords/Search Tags:Optical fiber sensors, Femtosecond laser direct writing technique, Fabry-Perot interferometer, Mach-Zehnder interferometer, Multi-mode interferometer, Single mode fiber, Refractive index, High-temperature
PDF Full Text Request
Related items