This paper presents a practical high-dimensional quantum key distribution (QKD) protocol over a deployed multicore fiber link in L'Aquila, Italy. The study addresses the challenge of increasing data transmission rates by proposing a 4-dimensional hybrid time-path-encoded QKD system. The system was tested over a 52-km multicore fiber link, which was formed by looping back two cores of a 26-km 4-core optical fiber. The experiment demonstrated the successful generation of secret keys with a final secret key rate (SKR) of 51.5 kbps through a channel loss of 22 dB. The results show that high-dimensional QKD can be robustly implemented in realistic environments by combining standard telecom equipment with emerging multicore fiber technology. The study highlights the advantages of high-dimensional QKD in terms of noise tolerance and secure-key generation rate, making it a promising candidate for future practical QKD systems.This paper presents a practical high-dimensional quantum key distribution (QKD) protocol over a deployed multicore fiber link in L'Aquila, Italy. The study addresses the challenge of increasing data transmission rates by proposing a 4-dimensional hybrid time-path-encoded QKD system. The system was tested over a 52-km multicore fiber link, which was formed by looping back two cores of a 26-km 4-core optical fiber. The experiment demonstrated the successful generation of secret keys with a final secret key rate (SKR) of 51.5 kbps through a channel loss of 22 dB. The results show that high-dimensional QKD can be robustly implemented in realistic environments by combining standard telecom equipment with emerging multicore fiber technology. The study highlights the advantages of high-dimensional QKD in terms of noise tolerance and secure-key generation rate, making it a promising candidate for future practical QKD systems.