Light sources and detection methods working in the quantum regime are elementary building blocks of quantum information systems. Our goal is the research and development on these devices, and on their application in communication and sensing. We develop a portable, robust, modular fibre-coupled entangled photon pair source which operates in the telecom wavelength range and enables us to implement quantum cryptography protocols. We investigate detection methods for the telecom wavelength range and make proposals for their development with regards to quantum efficiency, signal-to-noise ratio, detection rate and practical applicability. We test our devices in the quantum communication systems of the National Laboratory.