On the Security of Offloading Post-Processing for Quantum Key Distribution.

Quantum key distribution (QKD) has been researched for almost four decades and is currently making its way to commercial applications. However, deployment of the technology at scale is challenging because of the very particular nature of QKD and its physical limitations. Among other issues, QKD is computationally intensive in the post-processing phase, and devices are therefore complex and power hungry, which leads to problems in certain application scenarios.

Simple laser transmitter pair as polarization-independent coherent homodyne detector.

Coherent optical reception promises performance gains for a wide range of telecom applications and photonic sensing. However, the practical implementation and the particular realization of homodyne detection is by no means straight-forward. Local oscillator requirements and polarization management need to be cost-effectively supported for accurate signal detection at high sensitivity, preferably without relying on digital processing resources.

Analog receiver for coherent optical analog radio-over-fiber transmission.

A receiver for low-cost coherent optical applications is presented. Conceptual simplicity is guaranteed through the use of a monolithic integrated externally modulated laser. Local oscillators and fast photodetectors are provided by the distributed feedback section and electro-absorption modulator of the monolithic laser.

Perspectives and limitations of QKD integration in metropolitan area networks.

Quantum key distribution (QKD) systems have already reached a reasonable level of maturity. However, a smooth integration and a wide adoption of commercial QKD systems in metropolitan area networks has still remained challenging because of technical and economical obstacles. Mainly the need for dedicated fibers and the strong dependence of the secret key rate on both loss budget and background noise in the quantum channel hinder a practical, flexible and robust implementation of QKD in current and next-generation optical metro networks.

Bandpass sampling in heterodyne receivers for coherent optical access networks.

A novel digital receiver architecture for coherent heterodyne-detected optical signals is presented. It demonstrates the application of bandpass sampling in an optical communications context, to overcome the high sampling rate requirement of conventional receivers (more than twice the signal bandwidth). The concept is targeted for WDM coherent optical access networks, where applying heterodyne detection constitutes a promising approach to reducing optical hardware complexity.

Quaternary TDM-PAM as upgrade path of access PON beyond 10Gb/s.

A 20 Gb/s quaternary TDM-PAM passive optical network with chirped and non-linear optical transmitters is experimentally demonstrated. The migration from legacy TDM-PONs and the implications of using available 10 Gb/s components are analyzed. We show that a loss budget of 27.