Discriminator for separating back scattered raman light.

摘要

A discriminator for separating back scattered Raman light to separate the Stokes light and the anti-Stokes light from back scattered Rayleigh light includes a band filter (3). The discriminator also includes a pulsed source (1) of light of wavelength lambda a, a first lens (2A) collimating the light pulses from the source (1), a second lens (2B) condensing the beam of collimated light pulses to an optical fibre (5) and the reflective band filter (5) is provided in the optical path between the lenses (2A, 2B) to be oblique to the common optical axis of the lenses (2A, 2B). A wavelength separator (4) receives light reflected from the band filter (3). The band filter (3) allows a light substantially of wavelength lambda a to pass from the source (1) to the optical fibre (5) and cuts off light of wavelength lambda a+ DELTA lambda b and lambda a- DELTA lambda b. The band filter thus allows back scattered Rayleigh light of wavelength substantially lambda a to pass from the optical fibre (5) to the source (1). However, the reflecting band filter (3) reflects all of the back scattered Raman light comprising the Stokes light of wavelength lambda a+ DELTA lambda b, and the anti-Stokes light of wavelength lambda a- DELTA lambda b to the wavelength separator (4). This discriminator is useful in a thermometer for detecting the temperature of the optical fibre (5).