A Bragg grating based fibre optic reference beam laser Doppler anemometer

An in-line single mode optical fibre reference beam laser Doppler anemometer that utilizes the reflectivity of a Bragg grating as the source of the reference beam has been demonstrated. Tuning the emission wavelength of a laser diode across the bandwidth of a fibre Bragg grating (FBG) provides control of the amount of power in the reference beam, and thus a means for optimizing the signal to noise ratio.