Patent ID: 8120774

Claim:
An evanescent wave multimode optical waveguide sensitive to at least one of a chemical species and a physical parameter, the optical waveguide comprising: an optical waveguide core having a core refractive index; a cladding surrounding said core and having a cladding refractive index lower than said core refractive index for guiding light to be propagated in said optical waveguide such that an evanescent wave of said light propagates in said cladding, said cladding defining with said core an optical waveguide providing mode coupling such that multiple modes of the propagated light are continuously coupled while light propagates along said optical waveguide; and a chemical indicator in said cladding, said indicator comprising a chromoionophore for causing a variation of an optical absorption of said cladding as a function of said at least one of a chemical species and a physical parameter, said evanescent wave propagating in said cladding resulting in said light being at least partly absorbed by said indicator, said optical waveguide having a sensing portion provided with mode coupling means having a mode coupling length which is substantially shorter than a length of said sensing portion for causing continuous redistribution, along said sensing portion, between propagation modes of unabsorbed light power of said light as said light propagates.