The present invention relates to a continuously tuneable free space laser. An up-counter counts the number of the picture elements which emit light when the EL display panel is horizontally scanned, and the counting result thus obtained is outputted as an addressing signal to an EEPROM. In one design, received power in the sideband may be measured, e. , a hard boot, and goes through initial provisioning, the modem is in a steady state in which standard DOCSIS periodic ranging is performed.