The invention provides an
optical fiber humidity sensor with ultrahigh sensitivity and based on an all-
agar F-P cavity and a manufacturing method of the
optical fiber humidity sensor. The sensor comprises a leading-in
optical fiber and the
humidity-sensitive
agar F-P cavity composed of an
agar colloid. The leading-in optical
fiber and the agar F-P cavity are directly connected through an end face dipping method, the leading-in optical
fiber is used for leading in a
light source signal and transmitting reflected light, and the agar F-P cavity is used for sensing humidity changes in the environment. The agar
colloid has hygroscopicity because the surface of the agar
colloid contains a large number of hydrophilic groups, the agar colloid can expand when absorbing water and shrink when losing water, and the
refractive index and
size change at the same time. Changes of the
refractive index and thickness of an agar film are fully utilized for manufacturing the sensor, the ultra-short agar F-P cavity can be used as a sensing unit, and therefore ultrahigh sensitivity is obtained. Besides, agar
powder is cheap, easy to obtain and easy to dissolve in hot water, the cooled colloid is stable in
optical property, the
coating process is quite simple, a complicated operation process and expensive equipment are not needed, and the manufacturing cost of the sensor can be lowered.