Patent ID: 7024060

Claim:
A method for measuring the refractive index of a fluid, comprising the steps of: providing a waveguide, wherein the waveguide comprises a cylindrical rod having a first end face and a second end face; inputting a first light into the first end face of the waveguide, at a first angle of incidence to the first end face; inputting a second light into the first end face of the waveguide, at a second angle of incidence to the first end face, wherein the second angle differs from the first angle; detecting, using a single detection device, the first light and second light upon exit from the second end face, wherein the second light is detected subsequent to the first light being detected; and comparing, using the first and second angles, a measurement of the first light taken at the second end face to a measurement of the second light taken at the second end face, wherein the step of comparing automatically compensates for fluctuations in intensity of the first light and second light without the use of a reference measurement received external to the single detection device.