Experimental Demonstration for Co-existance of DPS-QKD Channel over C+L Transmission System

Considering the fact that quantum key distribution(QKD) require dark fiber, but laying new fiber or using an dedicated fiber for QKD may not be possible in all instance, a pratical situations consider where multiplexing involving the quantum channel required for DPS QKD and the classical situation present in the same fiber is done. Such a practical situation is realised experimentally to reveal that there exists trade off between classical data rate and secure key rate obtained by the QKD protocol. The existence of this trade-off indicates that in the above situation where quantum and classical channel coexists in a fiber or telecom operator would require to optimize classical channel power, channel separation and our results indicate that an operator will need to optimize in terms of classical channel power, channel separation, and number of channels to achieve a substantial key rate and data rate while operating over filled C and $\text{C}+\text{L}$ Band scenarios.