Mitsuhiro Iga

Terminated optical fiber sensor based on surface plasmon resonance for refractive index detection

A novel refractive index sensor has been presented which is characterized by the sensing part on the tip of the optical fiber. The principle of this sensor is based on surface plasmon resonance at the interface between gold and medium to be detected. In order to induce the evanescent wave interrogation, the proposed structure has been devised to deliberately leak the transmitted light into the cladding layer of the fiber by a mechanical cleaving and a thermal fusion splicing. The sensor response obtained from the spectral experiment exhibited availability in the use of spectral and optical intensity operation. The sensitivity for the case of spectral operation has achieved the values of 3.35*10-4 and 4.99*10-5 for 1.333 and 1.398 refractive index units, respectively.

Novel fiber optic sensor using heterocore structures and its applications

A novel structure of fiber optic sensor has been developed which is characterized by a short-length, different core- size fiber insertion in a fiber as a transmission network line. Two types of a macrobending sensor and an environment sensitive sensor are demonstrated. The macrobending sensor is expected in the use as multi-points (quasi-distributed) sensor. The environment sensitive sensor has the capability of interrogating with environmental conditions. The detailed structure and sensing principle of these new types of sensors are reported together with an experimental setup example arranged from the practical point of view and its attractive applications.

Optical fiber liquid-level sensor using a surface plasmon resonance

A liquid-level optical fiber sensor based on refractive index sensitivity of surface plasmon resonance has been proposed and demonstrated. The sensor can continuously measure a wide distance range in the liquids with a single fiber element, since the sensing interface is characterized on the fiber-cladding surface. The fiber element, having the gold film thickness of 70nm on the sensing surface, shows the capability for the use of refractive index to be sensed ranged from 1.333 to 1.428 RIU. The sensitivity has been experimentally achieved to be 2.86% change of the input light intensity per millimeter for the 40mm measurement range.