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Proceedings Paper

Refractive index sensor based on a combination of optical frequency comb with intracavity multi-mode interference fiber sensor
Author(s): R. Oe; T. Minamikawa; S. Taue; Y. Nakajima; K. Minoshima; T. Yasui
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Paper Abstract

Refractive index measurement is important for evaluation of liquid materials, optical components, and bio sensing. One promising approach for such measurement is use of optical fiber sensors such as surface plasmonic resonance or multimode interference (MMI), which measure the change of optical spectrum resulting from the refractive index change. However, the precision of refractive index measurement is limited by the performance of optical spectrum analyzer. If such the refractive index measurement can be performed in radio frequency (RF) region in place of optical region, the measurement precision will be further improved by the frequency-standard-based RF measurement. To this end, we focus on the disturbance-to-RF conversion in a fiber optical frequency comb (OFC) cavity. Since frequency spacing frep of OFC depends on an optical cavity length nL, frep sensitively reflects the external disturbance interacted with nL. Although we previously demonstrated the precise strain measurement based on the frep measurement, the measurable physical quantity is limited to strain or temperature, which directly interacts with the fiber cavity itself. If a functional fiber sensor can be installed into the fiber OFC cavity, the measurable physical quantity will be largely expanded. In this paper, we introduce a MMI fiber sensor into a ring-type fiber OFC cavity for refractive index measurement. We confirmed the refractive-indexdependent shift of optical spectrum event though the MMI fiber sensor is included in the cavity. Such the spectral shift was converted into refractive-index-dependent shift of frep via the wavelength dispersion of the cavity fiber.

Paper Details

Date Published: 28 August 2019
PDF: 4 pages
Proc. SPIE 11199, Seventh European Workshop on Optical Fibre Sensors, 111991D (28 August 2019); doi: 10.1117/12.2540787
Show Author Affiliations
R. Oe, Tokushima Univ. (Japan)
Japan Science and Technology Agency (Japan)
T. Minamikawa, Tokushima Univ. (Japan)
Japan Science and Technology Agency (Japan)
S. Taue, Kochi Univ. of Technology (Japan)
Y. Nakajima, Japan Space Technology Agency (Japan)
The Univ. of Electro-Communications (Japan)
K. Minoshima, Japan Space Technology Agency (Japan)
The Univ. of Electro-Communications (Japan)
T. Yasui, Tokushima Univ. (Japan)
Japan Science and Technology Agency (Japan)

Published in SPIE Proceedings Vol. 11199:
Seventh European Workshop on Optical Fibre Sensors
Kyriacos Kalli; Sinead O. O'Keeffe; Gilberto Brambilla, Editor(s)

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