**Author details**

*Applications of Optical Fibers for Sensing*

**5. Summary**

The broad spectral width of the resonance bands can also limit the multiplexing capabilities of the PMTP LPG. By utilising the double resonance bands, simultaneous measurements of surrounding refractive index and temperature were carried out for temperature ranges limited to ±3°C if the refractive index range is ±0.004

PMTP LPGs as versatile sensing platforms have become increasingly popular. The ultra-high sensitivity and quick response, as compared to other configurations of LPGs, proposes promising capabilities for use in many sensing applications. PMTP LPGs can be achieved by the precise choice of period or by post processing methods. However, the nature of their high sensitivity can also pose as limitations and sensors need to be optimised in order to avoid interference. By applying functional nanoscale coatings, it has been possible to tailor PMTP LPGs to have a preferred sensitivity to particular parameters. This opens the doors for a number of applications in the medical field for portable, real time monitoring. The sensors have potential deployment into the biochemical industry for measuring chemical concentrations and can also be applied to sense different gases in the environment. Specially designed sensors can also be used for monitoring food quality. However, calibration must be carried out first as the period and thickness of coating will affect the sensitivity of the sensor. More vigorous and consistent testing needs to be carried out before adoption in the healthcare and food safety industry [2]. Sensor packaging, ease of use and reusability are some aspects that need to be taken into consideration. As many chemical sensing applications take place in a solution, it may be beneficial to fabricate an LPG such that the appearance of the dual resonance bands will appear when the fibre is placed in solution. The fibre cladding size can greatly affect the sensitivity allowing a

RIU [87]. This information enables temperature calibrated sensing.

greater flexibility when designing an LPG at PMTP [49].

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Rebecca Yen-Ni Wong1 \*, Dora Hu Juan Juan1 , Morten Ibsen<sup>2</sup> and Perry Ping Shum3,4

1 Institute for Infocomm Research, Agency for Science, Technology and Research (A\*STAR), Singapore

2 Optoelectronics Research Centre, University of Southampton, Southampton, United Kingdom

3 Centre for Optical Fibre Technology, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore

4 CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, Singapore

\*Address all correspondence to: rebecca-wong@i2r.a-star.edu.sg

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
