Tapered long-period grating (TLPG) with Teflon AF coating for pressure sensing applications

This paper presents a simple and easy method of depositing a coating of Teflon AF onto a tapered long-period grating (TLPG) to enhance its pressure sensitivity. The coated TLPG was fixed in a pressure housing so as to assure that no elongation of the TLPG occurs during the process of pressure application, and that only the lateral pressure applied on the TLPG can contribute to the change of output spectrum of the TLPG. The pressure sensitivity of uncoated TLPG fabricated in our lab depends on the conditions of fabrication and was measured to be from 0.0040 to 0,0051 nm/bar. The measurement results show the pressure sensitivity of the Teflon AF coated TLPG is as high as 0.0066 nm/bar. This means that the pressure sensitivity of a TLPG can be enhanced by up to 57% with a suitable Teflon AF coating.