Extended Data Fig. 1: Thermo-optic switching tree demonstration.

a, The thermo-optic switches consist of a Mach–Zehnder interferometer with an electrical heater on each arm. b, Tuning curve for a single thermo-optic switch, showing optical power in the two outputs as a function of applied heater power. The use of two heaters allows the average electrical power consumption per switch to be halved. c, Output power distribution of the 1 × 16 transmitter switching tree for all switch settings, demonstrating clean switching. Output power was monitored using a set of monitor photodiodes at the output of the switching tree. d, On and off transients for a representative thermo-optic switch, demonstrating 90–10% switching times of 9.1 μs and 12.1 μs, respectively. Owing to minor thermal crosstalk between switches, the switching transients are not perfect decaying exponentials.