The access network portion of a telecommunications system in the last years demands ever-increasing bandwidth to serve not only residential and commercial customers but also other telecommunications operators, as is the case with back-haul in mobile infrastructure. To achieve this, technologies using fiber optics as a transmission medium are being developed. Passive Optical Network (PON) protocols such as ITU-T G.9804.1 provides new schemes of multiplexing that improve higher speed offered both in the downstream channel (operator to user) and in the upstream channel (user to operator). In some cases a symmetrical optical link is required to support new services, applications and terminals from users side because their profiles and demands has changed in the last decade with new challenges to maintain network parameters within the established contracted values. On the other hand, information security has also been a topic of interest in recent years, so quantum cryptography offers an alternative to increase robustness compared to the mechanisms available in electronic systems that could be vulnerable to the development of quantum computing. Although quantum cryptography protocols were defined in the last century, their application is of interest today, as they can exploit the properties of photons to make it more difficult for an intruder to obtain the private key of an information system that uses optical fiber as a transmission medium. This work shows the computational application of the BB84 quantum key distribution (QKD) protocol on an operating model of a 50G passive optical network, demonstrating both the cryptography performance and network quality parameters such as the bit error rate (BER) and the eye diagram.