Explain the underlying principles of Quantum Key Distribution (QKD), specifically focusing on the BB84 protocol. Your explanation should be suitable for an audience with a background in classical computer science but limited knowledge of quantum mechanics. Describe how the Heisenberg Uncertainty Principle and the No-Cloning Theorem contribute to the security of the key exchange. Discuss practical challenges in implementing QKD over fiber optic networks, including photon loss and decoherence.