A simple optical tachometer utilizing fibre optics and solid state electronics has been designed and constructed in order to monitor sample turbine spin speeds on a Varian HA 100D nuclear magnetic resonance spectrometer. By use of a bifurcated fibre optical path, light is transmitted to the turbine strobe, modulated, and returned to the detector within the same plastic-sheated glass fibre bundle. Rotational information can thus be retrieved without disturbing the magnetic field or sample environment. The relation of sample spinning speed to spectral quality is discussed.