Patent ID: 7615736

Claim:
An optical sensor comprising: a light source; a sensing unit having a reflecting surface and having a relative distance from an end surface of an optical fiber varying depending on physical quantities such as pressure and temperature; a first optical fiber transmitting light from the light source to the sensing unit; second and third optical fibers transmitting the light reflected from the reflecting surface of the sensing unit to a plurality of light-receiving portions, respectively; and a calculation unit calculating the physical quantities from a ratio of electrical signals from the light-receiving portions, wherein, end surfaces of the first to third optical fibers opposed to the reflecting surface are fixed so that the longitudinal direction of the optical fibers and the normal line of the reflecting surface form an angle θ, the second optical fiber and the third optical fiber are parallel to each other, the fixing angles of the first optical fiber and the second and third optical fibers are symmetric about the normal line of the reflecting surface, the first to third optical fibers have a single mode in the wavelength of which the optical fibers are used, and a depolarizer is interposed between the light source and the end surface of the first optical fiber.