High sensitivity evanescent field refractometer based on modal interference in micro-capillary wall

Wei Peng, Yun Liu, Xinpu Zhang, Fang Cheng, Ming Han

Research output: Contribution to journalArticle

8 Scopus citations


We present a novel fiber-optic refractive index (RI) sensor based on a short piece of fused-silica micro-capillary (FSC) spliced between single mode fibers (SMFs). The sensing element is the tubing wall of the FSC where multiple modes excited from the lead-in SMF interfere to form fringes that are collected by the lead-out SMF. Two types of sensors with symmetric and asymmetric structures are fabricated and tested. A single lead-in SMF is used in the symmetric structure, whereas two lead-in SMFs are used in the asymmetric structure. Experimental results show that both types of sensors have high RI sensitivities, the symmetric structure sensor has a quadrature response with a higher sensitivity in the tested RI range from 1.33 to 1.37, and the asymmetric structure has a linear RI response with a sensitivity of 580.41 nm/RIU in the same RI range. The RI sensing platform demonstrated here can be further developed as a miniaturized fiber optic biosensor for biological and biochemical analysis.

Original languageEnglish (US)
Article number6615930
Pages (from-to)430-435
Number of pages6
JournalIEEE Sensors Journal
Issue number2
Publication statusPublished - Feb 1 2014



  • Fiber optic sensor
  • Interference
  • Microcapillary
  • Refractive index

ASJC Scopus subject areas

  • Instrumentation
  • Electrical and Electronic Engineering

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