A new porous glass optical fiber has been developed for use as a sensor for the detection of ammonia vapors at low concentrations. The porous structure that remains after selective heat treatment, phase separation, and chemical leaching of a borosilicate glass imparts a high surface area to the fiber core. Ammonia vapors permeating into the porous zone, which is pretreated with a reversible pH dye indicator, produce a spectral change in transmission. The resulting pH change is measured by in-line optical absorbance and is proportional to the ambient-ammonia concentration. Ammonia-vapor concentrations as low as 0.7 part in 106 have been detected.
© 1988 Optical Society of America
Original Manuscript: July 16, 1987
Manuscript Accepted: February 2, 1988
Published: May 1, 1988
M. R. Shahriari, Q. Zhou, and G. H. Sigel, "Porous optical fibers for high-sensitivity ammonia-vapor sensors," Opt. Lett. 13, 407-409 (1988)