To ensure a significant variation in the quantity of light through a small bending deformation in pressure measurement using an optical fiber.
An optical fiber 10 has a regulated frequency (V value) lower than 90% of a regulated cut-off frequency providing single mode conditions for the wavelength of a practically available light source 61. More specifically, the optical fiber 10 has a relative index difference of core-clad smaller than that of a common communication optical fiber and has a light-leaky structure. The optical fiber 10, which is a pressure detection member, is subjected to bending deformation corresponding to the combustion pressure at each pressure receiving part 48a, b, c, d of a gasket 31 and a light receiving unit 62 detects variation of passing light quantity.
OBO SHIGERU
SHIMADA SATOSHI
FUMINO TAKAYUKI
SAKAGUCHI TATSUNORI
SASAYAMA TAKAO
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