Optical switches include a phase shifter on a first branch, a first heater on the first branch, and a second heater on a second branch. A hybrid coupler combines the first branch and the second branch. A first photodetector and a second photodetector are at outputs of the second hybrid coupler to measure crosstalk between the outputs of the second hybrid coupler. A controller is configured to activate the first heater or the second heater to reduce the measured crosstalk.