フレンケル励起子のエネルギー帯

Articledepartmental bulletin pape

曖昧で多義的なセクシュアリティを生きるLGBTQ 当事者の語り－「バイ」と「ノンケ」の二択を超えて－

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Fiber-optic distributed measurement of polarization beat length using slope-assisted Brillouin optical correlation-domain reflectometry

We demonstrate distributed measurement of the polarization beat length along single-mode optical fibers (SMFs) using slope-assisted Brillouin optical correlation-domain reflectometry (BOCDR) with high spatial resolution, long measurement range, high sampling rate, and single-end accessibility. The beat lengths of SMFs wound on mandrels with radii of 10.5, 7.5, and 3.4 cm are measured to be 36.0, 18.2, and 3.7 m, respectively, which agree well with theoretical calculations. This indicates that a unique beyond-nominal-resolution effect of slope-assisted BOCDR does not influence the measurement. Subsequently, distributed beat length measurement is demonstrated using an SMF comprising two sections wound on mandrels with different radii (10.5 and 3.4 cm).journal articl

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Potential of high-sensitivity tactile sensing using polymer optical fiber gratings

We characterize fiber gratings inscribed line-by-line in perfluorinated graded-index polymer optical fibers (PFGI-POFs) for tactile sensing. First, we measure the dependence of the wideband transmitted light spectrum on the distance between the fiber grating and an object composed of metal or rubber, clarifying that the spectral power is significantly dependent on the object position in a wide wavelength range. Subsequently, we experimentally show that this behavior is caused by the light scattering at the fiber grating, indicating that PFGI-POF gratings are potentially applicable to simple low-cost tactile sensors or high-sensitivity short-range displacement sensors with no need for additional supportive tools.journal articl

First demonstration of Brillouin optical correlation-domain reflectometry based on external modulation scheme

We demonstrate basic operation of Brillouin optical correlation-domain reflectometry (BOCDR) based on an external modulation scheme, which can mitigate three demerits of a conventional direct modulation scheme. A 0.8 m long strain in a 2.8 m long silica fiber is successfully detected in a distributed manner. This scheme can be employed not only in BOCDR but also in Brillouin optical correlation-domain analysis. (C) 2019 The Japan Society of Applied Physicsjournal articl

Trade-off relation between strain dynamic range and spatial resolution in slope-assisted Brillouin optical correlation-domain reflectometry

Slope-assisted Brillouin optical correlation-domain reflectometry (SA-BOCDR) is one of the high-speed distributed strain sensing techniques, but its strain dynamic range has been limited to approximately 0.15%, which is far from being sufficient for some practical applications. In this paper, we clarify that, unlike widely used time-domain techniques, SA-BOCDR has a trade-off relation between the strain dynamic range and the spatial resolution. This trade-off originates from the unique bell-shaped noise floor inherently involved in the Brillouin gain spectrum observed with correlation-domain techniques. We experimentally show that, at the cost of three times lowered spatial resolution, the strain dynamic range of >0.6% can be achieved.journal articl

Proof-of-concept demonstration of double-slope-assisted Brillouin optical correlation-domain reflectometry

We develop a new configuration of distributed strain and temperature sensing technology called double slope assisted Brillouin optical correlation domain reflectometry. Its loss independent operation is demonstrated through simplified simulation and proof of concept experiments using a standard silica single mode fiber.journal articl

Total spectral power-based method for estimating Brillouin frequency shift in optical fibers

A cost-effective method for estimating the Brillouin frequency shift (BFS) of the whole sensing fiber without using an electrical spectrum analyzer is developed. The Brillouin gain spectrum is down-converted and low-pass-filtered, and its total transmitted power is used to estimate the BFS. The strain dynamic range of this method is experimentally shown to be double the value of a conventional slope-assisted method.journal articl