Quantum physics in optical communication systems

Daniel F. Walls, Gerard J Milburn

Zhensen Gao, Ying Luo, Lihong Zhang +7 more

To guarantee information security from the lowest level of optical networks, it is essential to provide physical layer security in fiber-optic communication systems. However, it is challenging to realize high speed physical secure optical communication based on advanced optical modulation formats and pure commercial hardware components. In this work, we report an experimental demonstration of a high-speed 56 Gb/s PAM4 physical-layer secure optical communication system by employing an electro-optic self-feedback hardware module for temporal self-phase encryption and decryption without consuming any additional encryption channel. An encrypted 56 Gb/s PAM4 confidential signal is successfully decrypted after transmitting over 60 km single-mode fiber. The demonstrated scheme can not only be integrated with existing optical communication networks, but can also be used as a pluggable module, which may provide a promising solution for ultra-high speed physical secure optical communication by combining with advanced multiplexing technology in future.

Chao Lei, Rui Lin, Yajie Li +4 more

We propose and experimentally demonstrate a compatible physical-layer secure optical communication (PLSOC) system that integrates self-adaptive physical-layer key distribution (PLKD) and encryption (PLE) in optical coherent communication. Based on bit error rate difference of QAM signals mapped by asymmetric basis state Y-00 protocol, the secret key can be secretly exchanged over public fiber links without the pre-shared keys. Moreover, we perform a parameter self-adaptive strategy for practical and dynamic PLKD. The security of the key is evaluated in the case of a fiber-tapping attack. A secure hash algorithm, SHA3-512, is used to perform privacy amplification to obtain the virtually secure key. An error-free PLKD rate reaches 39.3 Kbits/s over 300 km ultra-low loss fiber. We experimentally enable the integration of the proposed PLKD scheme and quantum noise stream cipher (QNSC) with a single wavelength, same system. Q factor penalty of the integration system compared to the QNSC system is 3.7 dB (optical back-to-back) and 4.8 dB (300 km) respectively. By exploiting a common hardware platform, with the same wavelength, the proposed PLSOC system addresses the problem that PLKD and PLE are separately performed through independent optical fiber links or wavelengths. Since only digital signal processing is used, the scheme does not require extra hardware.

Horace P. Yuen

Apostol Vourdas

Yupeng Gong

Optical fibre networks are advancing rapidly to meet growing traffic demands. Security issues, including attack management, have become increasingly important for optical communication networks owing to the vulnerabilities associated with tapping light from optical fibre link. Physical layer security often requires restricting access to the channel and periodic inspection of the link performance. In this thesis, we report how quantum communication techniques can be utilized to detect a physical layer attack. We present an efficient method for monitoring the physical layer security of a high data rate classical optical communication network using a modulated continuous variable quantum signal. We describe the theoretical and experimental underpinnings of this monitoring system, and the monitoring accuracy for different monitored parameters. We analyze its performance in both unamplified and amplified optical links. The technique represents a novel approach in applying quantum signal processing to practical optical communication networks and compares well with classical monitoring methods. We also discuss the challenges in its practical application, its difference with existing quantum key distribution, and its usage in future secure optical transport network planning.