We proposed and analyzed a scheme of generating an optical multicarrier using a linear optical modulator–based hybrid interferometer modulator and a dual parallel Mach–Zehnder modulator. Fifteen-tone comb lines within 0.5-dB spectral power variation are obtained; the side-mode suppression ratio is about 35 dB; and the system is tolerant to radio-frequency phase differences. Some analysis on the noise characteristics and the impact of parameter drifting is also made. These features indicate that the proposed multicarrier generator is a good multiwavelength source for quantum key distribution wavelength division-multiplexing passive optical networks.
We proposed and analyzed a scheme of generating an optical multicarrier using a linear optical modulator–based hybrid interferometer modulator and a dual parallel Mach–Zehnder modulator. Fifteen-tone comb lines within 0.5-dB spectral power variation are obtained; the side-mode suppression ratio is about 35 dB; and the system is tolerant to radio-frequency phase differences. Some analysis on the noise characteristics and the impact of parameter drifting is also made. These features indicate that the proposed multicarrier generator is a good multiwavelength source for quantum key distribution wavelength division-multiplexing passive optical networks.
Implementation of the passive radio over-fiber technique permits modulating the low-frequency sub-carrier onto an optical channel for dissemination through a light-wave fiber network. Single-sideband modulation for optical signals allows the impressive utilization of channel capacity in optical fiber. Dispersion reduction techniques limit the pulse spreading of a propagated signal in any photonic scheme. To control pulse-spreading effects, the optical single-sideband modulation technique at different phase shifts is modeled, analyzed, and compared to examine the performance of a sub-carrier multiplexing system. Hence, in this paper, a quantum key distribution network using a single sideband modulation technique based on a Li-Nb Mach-Zehnder modulator has been proposed at different electrical phase shifts. In this suggested model, the Optisystem 14.2 simulator is used to analyze the nonlinear characteristics. We have designed a single-sideband contour reduction and amplification with each couplet of 120 km by increasing the distance up to 720 km, and the phase between quantum states is determined. The system performance of the suggested model is investigated and compared based on output power (dBm), quality factor, eye diagram, bit error rate (BER), extinction ratio (ER), and optical spectrum of the received signal by varying link distance (km), channel spacing (nm), input power (dBm), and fiber dispersion (ps/ns/km).
We propose orthogonal frequency-division multiplexing (OFDM), as a spectrally efficient multiplexing technique, for quantum key distribution at the core of trusted-node quantum networks. Two main schemes are proposed and analyzed in detail, considering system imperfections, specifically, time misalignment issues. It turns out that while multiple service providers can share the network infrastructure using the proposed multiplexing techniques, no gain in the total secret key generation rate is obtained if one uses conventional passive all-optical OFDM decoders. To achieve a linear increase in the key rate with the number of channels, an alternative active setup for OFDM decoding is proposed, which employs an optical switch in addition to conventional passive circuits. We show that by using our proposed decoder, the bandwidth utilization is considerably improved as compared to conventional wavelength-division multiplexing techniques.
We present a parallel quantum key distribution scheme, where a Mach–Zehnder (M–Z) interferometer is applied to achieve a subcarrier multiplexing quantum key distribution. The polarization of each sideband of the composite signal and their controlling factors are analyzed. The factors, such as intermodulation interference and laser source phase noise, which might increase quantum bit error, are studied. The simulation of the quantum bit error rate of the four different sidebands shows that this type of modulation can meet the bit error rate requirement of quantum key distribution.
The realization of large-scale, practical quantum key distribution (QKD) networks relies on the development of scalable architectures and integrated hardware. We demonstrate a metropolitan wavelength-division multiplexing (WDM) QKD network based on hybrid-integrated quantum node transceiver chips that integrate both transmitter and receiver functionalities, including high-speed pulse modulation, decoy-state modulation, tunable attenuation, time-bin encoding, and decoding. The packaged module offers a wavelength tuning range exceeding 85 nm, with its silicon photonic Mach–Zehnder modulator (MZM) achieving a single-photon equivalent dynamic extinction ratio (SP-EDER) of over 20 dB across the entire tuning range at a 1.25 GHz pulse repetition rate. In combination with a simple 1.25 GHz clocked integrated time-bin QKD system, we generate secret keys at a rate of 865.4 kbps over a channel with 9.08 dB of fixed attenuation and at a rate of 168.2 kbps over a distance of 80 km at 1550.12 nm. Our work demonstrates an integrated WDM QKD network capable of supporting scalable and cost-effective metropolitan quantum-secure communications.
Abstract Integrating quantum key distribution (QKD) into optical networks is a crucial step toward the adoption of quantum technologies in existing telecommunication fiber infrastructures. However, state-of-the-art solutions face significant challenges, including sensitivity to classical noise, particularly spontaneous Raman scattering, limited transmission distances, and varying network conditions. In this work, we present a novel discrete-variable QKD system running a time-bin BB84 protocol operating in the O-band (1295.56 nm), where the impact of dominant noise sources is effectively reduced. Combined with passive narrow-spectral filtering at the receiver, our system demonstrates robustness across diverse dense wavelength-division multiplexing scenarios, making it practical for real-world deployments. We validate its performance through extensive testing, showing stable key generation coexisting with different classical traffic conditions up to 17 dBm of total launch power. These results represent a significant advancement toward the integration of QKD into existing fiber networks, paving the way for secure quantum communication on a large scale.
We propose a scheme for continuous-variable quantum key distribution (CV-QKD) using the subcarrier multiplexing technique which was employed in microwave photonics. This scheme allows distribution of N channels with independent Gaussian-modulated CV-QKD in parallel with one laser source and several phase modulators. We analyze the influence of nonlinear signal mixing and security in the asymptotic limit. Results indicate that by using this multiplexing technique, each channel will have a non-Gaussian extra source noise, resulting in slight shortening of the maximum transmission distance, while the total secret key rate can be considerably increased. This scheme could also be used for key distribution for multiple users, and combined with wavelength division multiplexing devices it has potential to be used for construction of a CV-QKD network.