Research On Fiber Optic Temperature Sensor Based On PDMS Cavity Parallel Structure

Temperature plays an important role in daily life and engineering applications,especially in the preparation of chemical reagents,biological protein activity and temperature control in medical experiments,non-toxic,anti-electromagnetic interference and high-sensitivity temperature detection are essential.Due to the advantages of simple manufacturing,small size,low cost,stability and anti-electromagnetic interference,optical fiber sensor technology has attracted extensive attention from researchers,especially the optical fiber sensor based on Fabry-Perot Interferometer(FPI).In recent years,polydimethylsiloxane(PDMS)thermal sensitive materials have been used in FPI sensors,greatly improving the sensitivity of temperature measurement.In this paper,PDMS thermosensitive material and FPI are organically combined to design and study three new optical fiber temperature sensors based on PDMS cavity cascade.The specific research contents are as follows:A fiber optic temperature sensor based on the cascade of Sagnac ring and PDMS cavity is designed and prepared.First,the two ends of the panda fiber with a length of0.65 m are fused to the two output ends of the single-mode fiber coupler to form a fiber Sagnac ring with a free spectral range of 6.5 nm.Then,one end of the hollow core fiber(HCF)is welded to the single mode fiber(SMF),and the other end is cut.The length of the cut HCF is about 130?m,and then the liquid PDMS is filled with the HCF by capillary phenomenon,and then cured Then a PDMS cavity with a free spectral range of 6.9nm is formed.Finally,the Sagnac ring and the PDMS cavity are cascaded through a fiber circulator,and the interference spectrum after the cascade has an envelope,and the envelope shows a cursor phenomenon.The temperature experiment results show that the temperature response sensitivity of a single PDMS cavity is 1.15nm/~oC,while the temperature response of a single Sagnac ring is-1.40nm/~oC.Both interferometers have a very high response to temperature,and the response directions are opposite.Therefore,in the optical fiber vernier effect,both interferometers are sensing elements and each other is a reference element.Compared with the ordinary cursor effect,the sensitivity of the sensor is about 1 times higher.The temperature sensitivity of the sensor is-43.96nm/~oC,which is 38.2 times higher than that of a single PDMS cavity and 31.4 times higher than that of a single Sagnac ring.A parallel optical fiber temperature sensor based on dislocation fusion PDMS cavity and air cavity is designed and prepared.Firstly,an open FP cavity with a length of 102.3?m was prepared by SMF dislocation fusion.Then PDMS is filled into the open cavity to form a PDMS cavity.Then,the air cavity with SMF-ST-SMF structure was prepared by fusion,and the length of the air cavity was 162.2?m.Finally,the PDMS cavity is connected in parallel with the air cavity by optical fiber coupler,which causes the vernier effect.The experimental results show that the temperature sensitivity of a single PDMS cavity is 0.24nm/?,while the temperature sensitivity of a parallel air cavity is increased to 2.00 nm/?,and the sensitivity is amplified by 8 times.A parallel optical fiber temperature sensor with a dislocation fusion PDMS cavity and a quartz tube PDMS cavity is designed and prepared.Firstly,PDMS was filled into an open FP cavity prepared by SMF dislocation fusion to form a PDMS cavity with a length of 102.7?m.The PDMS is then filled with a SMF fused quartz tube of 87.8?m length to form another PDMS cavity.Finally,the PDMS cavity is connected in parallel to produce a vernier effect.The experimental results show that the temperature sensitivity of a single dislocation fused PDMS cavity and a quartz tube PDMS cavity is-0.24nm/?and 1.51nm/?respectively,and the sensor temperature sensitivity is-15.08nm/?after parallel connection.