pH sensor using Langmuir-Blodgett overlays on polished optical fibers

Evanescent coupling between a side-polished single-mode optical fiber and a single-mode, pH-sensitive Langmuir-Blodgett overlay is used to demonstrate an intrinsic fiber-optic pH sensor. The sensor shows a wavelength sensitivity of 18.8 +/- 0.8 nm/pH and a transmission sensitivity of 9.7 +/- 0.8 dB/pH when operating at 750 nm.