An optical fiber is used not only as a transmission medium but also as a sensor in fiber-optic sensing
technology. Novel specialty fibers and relevant technologies have been developed for various application
fields, such as avionics, infrastructures, atomic plants and oil&gas industries. In this paper, recent
progress in the fiber-optic sensing is reviewed with a focus on the specialty fibers and fiber-optic
components.
This paper describes the development and applications of a fiber-optic electric current sensing technique
with stable properties and sensing devices with a compact, simple, and flexible structure. We achieved
special sensor characteristics with a low birefringence fiber as the Faraday-effect sensing element and
also created sensing schemes that matched the fiber's features. By exploiting the sensing technique’s
excellent features, we developed various current monitoring devices and systems and applied them at an
electric power facility.
This paper reviews fiber optic sensor applications in the field of space engineering. Some of the R&D
activities introduced are; (1) structural health monitoring of cryogenic liquid hydrogen tanks, (2) FBGbased
hydrogen sensors, (3) thermal strain monitoring of sensing coils in fib
Fiber-optic sensing technique using a thin-film bandpass filter was demonstrated. A bandpass filter on
fiber-end (BOF) sensor has broad spectrum curve which can detected by simple reflectometer. It has a
possibility to construct inexpensive multi-sensing systems. BOF sensor can detect ordinary temperature
with accuracy of ± 0.5˚C, and it has possibility to use for fiber-optic pressure sensing and hydrophone.
Tilted Fiber Bragg Grating (TFBG) is expected to be used for such sensors as refractometers, twist
sensors, liquid level sensors, chemical sensors and biosensors. We review its fabrication techniques and
its refractive index measurements and developed a simplified technique to fabricate TFBG for
simultaneous measurements of the refractive index and the temperatures of liquids. We used a
combination of a 4ω Nd:YAG laser and a phase mask, which is simpler than a conventional method
using a 2ω cw Ar+ laser and a Lloyd mirror interferometer. We calculated TFBG’s cladding modes by
the multi-layer method and estimated the temperature coefficient of the water’s refractive index to be
about ‒1×10‒4 /K using our fabricated TFBG sensor.