An apparatus comprises a laser emitter configured to transmit laser energy across an air gap to a separate device; a mobile industry processor interface (MIPI); driver circuitry electrically coupled to the laser emitter, wherein the driver circuitry is configured to receive an electrical signal according to an MIPI protocol and drive the laser emitter according to the electrical signal; a tone circuit configured to generate a tone signal of a specified tone frequency; and an MIPI mode detection circuit electrically coupled to the driver circuitry and the MIPI, wherein the MIPI mode detection circuit is configured to detect a change between a MIPI low power (LP) mode and a MIPI high speed (HS) mode at the MIPI interface, and add the tone signal to an electrical signal provided to the driver circuitry from the MIPI according to the detected change.