We have demonstrated switching characteristics in a wavelength switch based on multiple GaInAs/InP quantum wells. It consisted of straight arrayed waveguides with a linearly varying refractive index distribution. The refractive index can be changed via the thermo-optic (TO) effect. Using a Ti/Au thin-film heater to generate the TO effect, we realized four-port switching at four demultiplexed wavelengths. In addition, by changing the structure of the heater from rectangular to triangular, the power consumption for four-port switching was reduced by half.