m of laser 6 also in this case the ratio between resistor 3 and resistor 5 is 10 so that the injection efficiency amounts to 90 the modulating signal v s is applied via the decoupling capacitor 11 to the base of transistor 13 when transistor 13 is in a cutoff condition it supplies no current whatsoever and a current i l equal to the bias current i p only will circulate within laser 6 which will not emit a significant amount of power when transistor 13 is in a saturation condition it supplies the modulation current i m which is added to the bias current i p the current circulating within laser 6 is consequently a current i l i p i m and laser 6 will emit power also in this second solution the variable direct voltages v rb and v rm are used to regulate the bias current i p and the modulation current i m in the manner explained above in addition this second solution affords the possibility of a completely independent regulation of the bias current i p and of the modulation current i m in both solutions illustrated above the switch over of one transistor only is sufficient to cause the transition from an emission of power condition to a non emission of power condition in laser 6 and for this reason the driver is particularly fast in fact from measurements made in the lab switching times range from 3 u00d7 10 10 sec to 5 u00d7 10 10 sec resistor 12 is sized so as to adapt the modulating signal v s level to the level of the signal required to control transistor 7 or transistor 13 whilst the task of capacitor 11 is to stop my possible direct current component which.