We report on a microelectromechanical-systems (MEMS)-based 1 x N wavelength-selective switch (WSS) with excellent open-loop stability and repeatability. The optical power fluctuation of the WSS is < +/-0.0035 dB over a 3.5-h period. The variation of optical power during 30 ON-OFF switching periods is < +/-0.0026 dB. Experiments were also performed on the analog MEMS mirror. The stability and repeatability are +/-0.00085degrees and +/-0.0013degrees, respectively.