Search

A digital VCSEL driver has been designed, simulated and assessed under radiation, using discrete SiGe HBTs. The circuit tolerates high levels of gamma radiation, up to 12 MGy, features less than 2% drift in the forward current of the VCSEL and operates well above 10 MHz. The output duty cycle shows no notable degradation at 200 kHz, enabling the design of robust analog and digital communication systems using pulse-width-modulation (PWM) schemes. [ABSTRACT FROM AUTHOR]

Future maintenance tasks of the International Experimental Thermonuclear fusion Reactor (ITER) will require communication links between the remotely operated equipment in the reactor vessel and the control room, that are radiation tolerant up to MGy dose levels. We therefore assessed the DC behaviour of a COTS SiGe heterojunction bipolar transistor (HBT) under gamma radiation up to more than 4 MGy. The DC current gain (β) presents a limited loss of about 30% for a base current of 100 μA. Our in-situ measurements allowed us to adapt the manufacturer's SPICE model and account for these radiation effects. Circuit-hardened driving electronics for both photonic transmitters and receivers can hence be designed. [ABSTRACT FROM AUTHOR]