Quantum key distribution (QKD) constitutes a symmetric secret key negotiation protocol capable of maintaining information-theoretic security. Given the recent advances in QKD networks, they have evolved from academic research to some preliminary applications. A QKD network consists of two or more QKD nodes interconnected by optical fiber or free space links. The secret keys are negotiated between any pair of QKD nodes, and then they can be delivered to multiple users in various areas for ensuring long-term protection and forward secrecy. We commence by introducing the QKD basics, followed by reviewing the development of QKD networks and their implementation in practice. Subsequently, we describe the general QKD network architecture, its elements, as well as its interfaces and protocols. Next, we provide an in-depth overview of the associated physical layer and network layer solutions, followed by the standardization efforts as well as the application scenarios associated with QKD networks. Finally, we discuss the potential future research directions and provide design guidelines for QKD networks.

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The Evolution of Quantum Key Distribution Networks: On the Road to the Qinternet

This paper reports on modern features of the optical-label switching (OLS) system in support of multicast, optical time-to-live (TTL), and video-streaming applications. We first propose and demonstrate optical-label switching core router architecture with multicast function. The multicast switching architecture provides reduced complexity and effective multicast contention resolution compared to conventional multicast-capable switching fabric. A proof-of-principle experiment successfully showed packet multicast forwarding with contention resolution. The all-optical TTL monitors the healthiness of the packet, and prevents degraded packets from traveling or looping further in the network. The experiment demonstrated successful packet discards based on optical signal-to-noise ratio degradation. Finally, we present an optical label switching edge router that supports aggregation, quality of service, and class of service, and we further demonstrate a video streaming application between Ethernet clients through the OLS edge routers and a core router. The modern features of OLS routers proposed and demonstrated in this paper indicate the viability of OLS technologies in future photonic Internet in support of modern applications.

Advanced optical-label routing system supporting multicast, optical TTL, and multimedia applications

A simple and effective coarse wavelength-division-multiplexing metro access network architecture with unidirectional optical add-drop multiplexer (OADM) for automatic optical protection in a hub/access-node single-fiber ring is proposed and experimentally demonstrated. This physical-ring/logical-star architecture greatly simplifies the design compared with previous works requiring bidirectional OADM.

Demonstration of a single-fiber self-healing CWDM metro access ring network with unidirectional OADM

A review on all-optical logic adder: Heading towards next-generation processor

We propose and demonstrate a new bidirectional optical add-drop multiplexer (BOADM) with gain based on multiport optical circulators and fiber Bragg gratings. The BOADM incorporates a single unidirectional optical amplifier and can flexibly accommodate asymmetric traffic. The device achieves more than 13 dB of bidirectional gain and has low in-band crosstalk (below -45 dB) and low out-of-band crosstalk (below -30 dB). Moreover, the device removes Rayleigh backscattered light and out-of-band amplified spontaneous emission noise. The power penalty is negligible for all through and add-drop channels in both directions when the BOADM is used in a 6 /spl times/ 10 Gb/s bidirectional wavelength-division-multiplexing transmission system over 80 km of standard single-mode fiber.

A bidirectional optical add-drop multiplexer with gain using multiport circulators, fiber Bragg gratings, and a single unidirectional optical amplifier

Fiber Bragg grating (FBG) based rearrangeable nonblocking optical cross connects (OXC's) using multiport optical circulators are proposed in this letter. The use of multiport optical circulators instead of three-port circulators can be more efficient for large optical cross connects systems. Performance evaluations of proposed large dimension optical cross connects are investigated.

Fiber Bragg grating-based rearrangeable nonblocking optical cross connects using multiport optical circulators

A wavelength conversion technique which can convert an input signal to many wavelengths simultaneously without any probe laser is proposed. 622 Mb/s one-to-six wavelength conversion and multicast in a bus network are demonstrated.

Single to multi wavelength conversion using amplified spontaneous emission of semiconductor optical amplifier

A novel single-fiber bi-directional optical add/drop multiplexer is proposed for wavelength division multiplexing distribution networks. It has the advantages of low insertion loss, low cost, and providing protection function passively to the distribution ring network.

A novel single-fiber bidirectional optical add/drop multiplexer for distribution networks

A new wavelength conversion technique using the amplified spontaneous emission of a semiconductor optical amplifier isproposed. The technique allows signals of a particular wavelength to be converted to many wavelengths simultaneouslywithout the need of any probe laser. A 622Mb/s one-to-six wavelength conversion system has been demonstrated over a busnetwork.Keywords: wavelength conversion, semiconductor optical amplifier, wavelength division multiplexing, optical networks 1. INTRODUCTION All-optical wavelength conversion is important to the future development of optical networking because it is able to enhancethe flexibility and transparency, and increase the capacity of wavelength division multiplexing (WDM) networks. Thewavelength conversion techniques proposed previously involve the use of cross-gain modulation, cross-phase modulation andfour-wave mixing in semiconductor optical amplifiers (SOA) 1 . The limitations of these techniques are that they all need aprobe laser, and can only convert an input wavelength to another wavelength, which is determined by the wavelength of theprobe laser. The ability of a wavelength converter to replicate signals carried on one wavelength to many differentwavelengths is an important feature for such applications as video distribution and teleconferencing over a WDM network

Single- to multiwavelength conversion using amplified spontaneous emission of semiconductor optical amplifier

An on-chip continuous-variable quantum key distribution(CV-QKD) system is integrated using silicon photonics fabrication process and demonstrates the capability of transceiving Gaussian-modulated coherent states and homodyne detection.

Yunfeng Shen

Papers

Fiber Bragg grating-based rearrangeable nonblocking optical cross connects using multiport optical circulators

Single to multi wavelength conversion using amplified spontaneous emission of semiconductor optical amplifier

A novel single-fiber bidirectional optical add/drop multiplexer for distribution networks

Single- to multiwavelength conversion using amplified spontaneous emission of semiconductor optical amplifier

On-Chip Continuous-Variable Quantum Key Distribution(CV-QKD) and Homodyne Detection