Contents 1. Introduction
Optical quantum key distribution (QKD) is a highly secure communication technology employing advanced cryptographic protocol to modulate either the polarization or the phase of a single-wavelength and narrow linewidth laser typically. By using the master-to-slave injection locking to encrypt the QKD code stream delivered by the master laser diode onto the phase of a slave laser diode, the source message encoded to the single-photon quantum carrier can be deployed over the dense-wavelength-division-multiplexing (DWDM) channels for performing one-way non-stealable/non-interceptable information between transmission and receiving. Nevertheless, some drawbacks must be overcome for the QKD, such as the increased complexity of the encryption, the improvement of the data origin authentication, and so on. Wavelength switchable and lockable source has recently been promoted as an emerging DWDM carrier to facilitate benefits from the easy selectivity of channel carriers. Such a superiority can considerably be adapted to perform the QKD if both phases and wavelength can be coherently controlled via optical injection. This operation can concurrently approach the complexity and preserve the data origin authentication via the single-photon transmission with wavelength certainly between on/off optical injection-locking (OIL) conditions. In this work, the QKD encryption through the selective wavelength injection-locking and phase shift keying of a dual-mode distributed feedback laser diode (DFBLD) effectively adds one dimension of the encryption in addition to the polarization and phase of the optical carrier used for carrying the quantum key. The wavelength switching, phase shift-keying (PSK), and quantum-key coding are investigated in detail to realize the advanced QKD with wavelength uncertainty.
