Takeshi YAGI,¹ Naofumi KUBOKI,² Yoshihisa SUZUKI,¹ Naotaka UCHINO,² Kazunori NAKAMURA² and Kazuaki YOSHIDA^2,*

¹The Furukawa Electric Co., Ltd., Opto-Technology Laboratory, 6, Yawata-kaigandori, Ichihara, Chiba, 290 Japan, ²The Furukawa Electric Co., Ltd., Yokohama R&D Laboratories, 2-4-3, Okano, Nishiku, Yokohama, 220 Japan

(Received April 8, 1997; Accepted June 9, 1997)

A new fiber-optic ammonia sensor utilizing rectangular-cladding eccentric-core fiber and a sensitive film containing an indicator dye is demonstrated. The sensitive film is a SiO₂-GeO₂ gel film including an indicator dye of bromocresol purple or bromocresol green, which is dip-coated by a sol-gel technique. The attenuation of this sensor changes depending on the concentration of ammonia at the wavelength range of 500-700 nm. This sensor can detect several ppm of gaseous ammonia. Various factors determining the sensitivity to detect the ammonia gas and time response of the sensor are also studied.

Key words : fiber-optic ammonia sensor, rectangular-cladding eccentric-core fiber, indicator dye, attenuation, sol-gel technique, gaseous ammonia

*yoshida@yokoken.furukawa.co.jp