**5. Summary**

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

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**Author details**

Rebecca Yen-Ni Wong1

(A\*STAR), Singapore

United Kingdom

provided the original work is properly cited.

© 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,

\*, Dora Hu Juan Juan1

1 Institute for Infocomm Research, Agency for Science, Technology and Research

2 Optoelectronics Research Centre, University of Southampton, Southampton,

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

3 Centre for Optical Fibre Technology, School of Electrical and Electronic

Engineering, Nanyang Technological University, Singapore

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

, Morten Ibsen<sup>2</sup>

and Perry Ping Shum3,4

*Optical Fibre Long-Period Grating Sensors Operating at and around the Phase Matching…*

*DOI: http://dx.doi.org/10.5772/intechopen.81179*

*Optical Fibre Long-Period Grating Sensors Operating at and around the Phase Matching… DOI: http://dx.doi.org/10.5772/intechopen.81179*
