Hybrid grating in reduced-diameter fiber for temperature-calibrated high-sensitivity refractive index sensing

Biqiang Jiang*, Zhen Hao, Dingyi Feng, Kaiming Zhou, Lin Zhang, Jianlin Zhao

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We propose and experimentally demonstrate a hybrid grating, in which an excessively tilted fiber grating (Ex-TFG) and a fiber Bragg grating (FBG) were co-inscribed in a reduced-diameter fiber (RDF). The hybrid grating showed strong resonances due to coupling among core mode and a set of polarization-dependent cladding modes. This coupling showed enhanced evanescent fields by the reduced cladding size, thus allowing stronger interaction with the surrounding medium. Moreover, the FBG's Bragg resonance confined by the thick cladding was exempt from the change of the surrounding medium's refractive index (RI), and then the FBG can work as a temperature compensator. As a result, the Ex-TFG in RDF promised a highly sensitive RI measurement, with a sensitivity up to ~1224 nm/RIU near the RI of 1.38. Through simultaneous measurement of temperature and RI, the temperature dependence of water's RI is then determined. Therefore, the proposed hybrid grating with a spectrum of multi-peaks embedded with a sharp Bragg resonance is a promising alternative for the simultaneous measurement of multi-parameters for many RI-based sensing applications.

Original languageEnglish
Article number1923
JournalApplied Sciences (Switzerland)
Issue number9
Publication statusPublished - 10 May 2019

Bibliographical note

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).


  • Fiber Bragg grating
  • Refractive index sensing
  • Temperature dependence of the refractive index of water
  • Tilted fiber grating


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