'Institute of Electrical and Electronics Engineers (IEEE)'
Abstract
Quantum key distribution (QKD) systems that use weak coherent states often rely on attenuated lasers to generate signals with an average of less than one photon per pulse. Two ways of attenuating laser light in a weak, coherent, integrated QKD transmitter chip are compared in terms of noise, namely attenuation with Mach-Zehnder (MZ) interferometers and attenuation with semiconductor optical amplifiers (SOAs) biased as attenuators. Results from simulations and experiments on the optical spectrum of the output of the transmitter chip show that under reverse bias conditions the SOAs result in similar noise levels as the MZs. The footprint of the SOAs on the chip, however, is more than 50 times smaller than that of the MZs. This makes them the better candidate for the integrated, weak coherent QKD source
