Fiber-based curvature sensors,especially those capable of discerning the direction of curvature,have attracted more and more interest due to their promising applications in structural health monitoring,high-precision ...Fiber-based curvature sensors,especially those capable of discerning the direction of curvature,have attracted more and more interest due to their promising applications in structural health monitoring,high-precision measurement,medical and biological diagnosis-treat instruments,and so on.Here,we propose and demonstrate a compact directional curvature sensor that comprises two bridged waveguides and three Bragg gratings in a section of three-core fiber(TCF).Both the waveguides and gratings are integrated by femtosecond laser micromachining method.The waveguides,connecting the TCF outer cores to the lead-in single-mode fiber core,function as beam couplers to realize simultaneous interrogation of all three gratings without any separate fan-in/out component.Owing to the spatial specificity,the outer-core gratings exhibit high and direction-dependent sensitivity to curvature,whereas the central-core grating is nearly insensitive to curvature but shows similar sensitivities to ambient temperature and axial strain as the outer-core gratings.It can be used to compensate the cross impact of temperature and strain when the outer-core gratings are applied for curvature detection.Moreover,the wavelength interval between two outer-core gratings is also proposed as an indicator for curvature sensing.It features with a much higher sensitivity to curvature and reduced sensitivities to temperature and axial strain.The corresponding maximum sensitivity to curvature is as high as 191.89 pm/m-1,while the sensitivities to temperature and strain are only 0.3 pm/℃and 0.0218 pm/με,respectively.Therefore,our proposed device provides a compact and robust all-infiber solution for directional curvature sensing.It not only offers high sensitivity and accuracy but also immunity to temperature and axial strain fluctuations,making it a promising tool for a wide range of applications.展开更多
文摘Fiber-based curvature sensors,especially those capable of discerning the direction of curvature,have attracted more and more interest due to their promising applications in structural health monitoring,high-precision measurement,medical and biological diagnosis-treat instruments,and so on.Here,we propose and demonstrate a compact directional curvature sensor that comprises two bridged waveguides and three Bragg gratings in a section of three-core fiber(TCF).Both the waveguides and gratings are integrated by femtosecond laser micromachining method.The waveguides,connecting the TCF outer cores to the lead-in single-mode fiber core,function as beam couplers to realize simultaneous interrogation of all three gratings without any separate fan-in/out component.Owing to the spatial specificity,the outer-core gratings exhibit high and direction-dependent sensitivity to curvature,whereas the central-core grating is nearly insensitive to curvature but shows similar sensitivities to ambient temperature and axial strain as the outer-core gratings.It can be used to compensate the cross impact of temperature and strain when the outer-core gratings are applied for curvature detection.Moreover,the wavelength interval between two outer-core gratings is also proposed as an indicator for curvature sensing.It features with a much higher sensitivity to curvature and reduced sensitivities to temperature and axial strain.The corresponding maximum sensitivity to curvature is as high as 191.89 pm/m-1,while the sensitivities to temperature and strain are only 0.3 pm/℃and 0.0218 pm/με,respectively.Therefore,our proposed device provides a compact and robust all-infiber solution for directional curvature sensing.It not only offers high sensitivity and accuracy but also immunity to temperature and axial strain fluctuations,making it a promising tool for a wide range of applications.
