Abstract
A novel in-fiber Mach-Zehnder interferometer based on cascaded up-down-taper (UDT) structure is proposed by sandwiching a piece of polarization maintaining fiber between two single-mode fibers (SMF) and by utilizing over-fusion splicing method. The dual up tapers respectively act as fiber splitter/combiner, the down taper acts as an optical attenuator. The structure parameters are analyzed and optimized. A larger interference fringe extinction ratio ~15 dB is obtained to achieve refractive index (RI) sensing based on intensity demodulation. The experimental results show that the RI sensitivity is −310.40 dB/RIU with the linearity is improved to 0.99 in the range of 1.3164–1.3444. The corresponding resolution can reach 3.22 × 10−5 RIU, which is 6.8 times higher than wavelength demodulation. The cross sensitivity which caused by temperature fluctuation is less than 1.4 × 10−4.
Highlights
Optical fiber refractive index (RI) sensors are used in biological fields, medicine and environment [1,2,3]
Lots of fiber optic RI sensors have been reported in the literature, such as
The structure can be used as an all-fiber type device integrating double optical beam splitters/combiners and an optical attenuator
Summary
Optical fiber refractive index (RI) sensors are used in biological fields, medicine and environment [1,2,3]. Kong core fiberataper and an air bubble fabricated by the arc discharge exhibits designed hybrid multi-mode interferometer which consisting of technique, a thin core which fiber taper and aanhigh air RI sensitivity of 442.59. Using erbium-doped tapered microfiber intensity attenuator in a dual-wavelength erbium-doped relative high sensitivity of 273.7asdB/RIU is obtained. The proposed structure does not itpolarization can avoid polarization modeon coupling transmission and effectively reduce the influence of require largemode instrument and complicated manufacturingAdditionally, process, andthe weproposed can get this structure by polarization dispersion on sensing performance. The temperature which cross talk is less than has a high sensitivity dB/RIU in the range of Such athan structure the advantages of smallThe size,temperature low cost and lesstalk temperature can be higher that inwith wavelength demodulation. Structure with the advantages of small size, low cost and less temperature crosstalk can be applied in the fields of high precision detection of RI test
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