A Fiber M-Z Interferometer Curvature Sensor Based On Double Helix Structures

Fiber-based technology has been comprehensively and rapidlydeveloped since optical fiber being generated.The special performance of the fiber makes it play a pivotal role in the field of sensing and communication.Because fibersensor has many of the advantages of the researchers with other types of sensors do not have.The fiber optic sensor has been widespread concern.These advantages include fiber optic sensor size is small,faster response,anti-electromagnetic interference and so on.At present,the common optical fiber sensors are mainly divided into two categories,namely fiber interferometer type sensor and fiber grating type sensor.The fiber optic interferometer sensor is more widely used in engineering monitoring than fiber grating sensors with higher sensitivity and lower cost.As an important branch of the fiber optic interferometer sensor,a variety of new fiber-optic Mach-Zehnder(MZ)interferometer sensors have emerged in recent years.In this paper,a Mach-Zehnder(MZ)interferometer fiber-optic sensor based on double helix(DHS)is fabricated by means of fiber fusion splicing and manual rotation of the fiber.One end of the fiber with the cating layer can be fixed by the clamp frameworkof the fiber fusion splicer and the other end of the fiber with no cating layer can be rotated by hand.To achievethe structure,the fiber is arc-discharged by the fusion splicer to soften and thenrotate one end of the fiber manually.The morphology of this structure and the preparation process can be observed by CCD of the fiber fusion splicer.Here the discharge current is set to 13 mA and the discharge time is 200 ms.The same way can be used in the same fiber to prepare another spiral structure,the two spiral structures mainly play a role of mode coupling and re-coupling.The structure of the MZ interferometer with the same SMF structure is only 7mm in length,and the prepared device does not change the original diameter of the fiber,thus ensuring the mechanical strength of the fiber.The experimental results show that the transmission spectra of the device are blue-shifted with the increase of the bending curvature and the bending sensitivity exhibits a good linear relationship with the increase of the bending curvature.For the interference peak at the wavelength of 1520 nm,the maximum sensitivity is-35.27nm/m-1 in the range of bending curvature from 0.5m-1 to 3.059m-1,so the bending sensitivity of the device is high.In addition,our sensor response characteristics of the temperature were also tested in the external temperature range of 30?-90?,the device temperature sensitivity of only 63 pm/?.And the cross sensitivity of the device to do the analysis,the device temperature relative to the bending sensitivity of the cross sensitivity of 0.0018 m-1/ ?,so the device temperature cross-sensitivity is low,can be used as a bending sensor.Because of its compact structure,easy preparation,low production cost,high bending sensitivity and low temperature cross sensitivity,it has potential application prospect in the field of engineering application sensing.