A Multimode Fibre‐coupled Compact Optical Wavelength Meter based on Wollaston Prisms

We present a compact, portable, and mechanically robust instrument for measuring optical wavelength based on an arrangement of four Wollaston prisms that forms spatially localised fringes in a plane perpendicular to the optic axis. The wavelength is determined from the fringe period. After calibration, the instrument had an accuracy of c. 1o f 10 6 , and was immune to fluc- tuations in output intensity of a light source of up to 10 dB.