Patent ID: 7859662

Claim:
An on-vehicle fuel property detection device comprising: a conduit disposed in a fuel tank or between a fuel pump and said injector of the vehicle; an optical fiber disposed inside the conduit and composed of a core in a part of which a grating is applied, a clad covering the core, and a fiber jacket covering the clad in which a portion corresponding to the part which said grating is applied is removed so that said clad is in contact with a fuel fed to an injector of a vehicle; a light source disposed on one end of the conduit and entering a light being in a range of clad mode wavelengths of said grating to said optical fiber; and a light-sensitive part disposed on the other end of the conduit and detecting an intensity of the light transmitting through the region to which said grating is applied; wherein said conduit is provided with a fuel inlet and a fuel outlet, each are open in the direction different from an axial direction of the conduit.