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Conference on Lasers and Electro-Optics

Long Range Secure Key Distribution Over Multiple Amplified Fiber Spans Based on Environmental Instabilities

Ben Wu, Yue-Kai Huang, Shaoliang Zhang, Bhavin J. Shastri, Paul R. Prucnal

Published Jan 1, 2016• 11 citations
Publisher

Abstract

Using environmental instability induced signal phase fluctuation, we demonstrated a secure key distribution system over a 240-km bidirectional fiber-pair link. The scheme is compatible with commercial WDM systems and optical amplifiers for long-range transmissions.
DOI
10.1364/cleo_si.2016.sf1f.4

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We proposed and experimentally demonstrated a secure key generation and distribution system that is compatible with optical amplifiers and standard wavelength-division multiplexing (WDM) transmission systems. The key is generated from the phase fluctuations induced by environmental instabilities. The key generation system is tested in a 240 km bidirectional fiber-pair link with multiple optical amplifiers. To demonstrate the compatibility with WDM systems, 38 WDM channels are transmitted together with the key distribution channel. The secret key is protected against eavesdropping and coherence detection attack by the wide-band property of the signal carrier and the fast-changing rate of the phase fluctuations.
We propose a secure key generation and distribution scheme for data encryption in classical optical fiber channel. A Delay interferometer (DI) is used to track the random phase fluctuation inside fiber, while the reconfigurable lengths of polarization-maintaining (PM) fiber are set as the source of optical phase fluctuations. The output signals from DI are extracted as the secret key and shared between the two-legal transmitter and receiver. Because of the randomness of local environment and the uniqueness of fiber channel, the phase fluctuation between orthogonal polarization modes (OPMs) can be used as secure keys to enhance the level of security in physical layer. Experimentally, we realize the random key generation and distribution over 25-km standard single-mode fiber (SSMF). Moreover, the proposed key generation scheme has the advantages of low cost, compatible with current optical fiber networks and long distance transmission with optical amplifiers.
Abstract In traditional communication systems the transmission medium is considered as a given characteristic of the channel, which does not depend on the properties of the transmitter and the receiver. Recent experimental demonstrations of the feasibility of extending the laser cavity over the whole communication link connecting the two parties, forming an ultra‐long fiber laser (UFL), have raised groundbreaking possibilities in communication and particularly in secure communications. Here, a 500 km long secure key distribution link based on Raman gain UFL is demonstrated. An error‐free distribution of a random key with an average rate of 100 bps between the users is demonstrated and the key is shown to be unrecoverable to an eavesdropper employing either time or frequency domain passive attacks.
We propose and experimentally demonstrate an approach to generate and distribute secret keys over optical fiber communication infrastructure. Mach-Zehnder interferometers (MZIs) are adopted for key generation by transferring the environmental noise to random optical signals. A novel combination of wideband optical noise and an asymmetric MZI structure enables the secret keys to be securely transmitted and exchanged over public fiber links without being detected. We experimentally demonstrate this system and show reliable performance: keys are generated at the rate of 502 bit/s, and are successfully exchanged between two parties over a 10 km optical fiber with a bit error of ∼ 0.3%. System security analysis is performed by corroborating our experimental findings with simulations. The results show that our system can protect the key distribution under different attacks, attributed to wideband optical noise and asymmetric MZI structures. Compared to the previous schemes based on distributed MZIs, our scheme exploits localized MZI which provides twofold advantages. Firstly, the key generation rate can be increased by a factor of 5.7 at a negligible additional cost. Secondly, the system becomes robust to, in particular, active intrusion attack. The proposed system is a reliable and cost-effective solution for key establishment, and is compatible with the existing optical fiber communication infrastructure.
To share the reciprocity of a single fiber channel in physical-layer secure key distribution (PLSKD), the bidirectional same wavelength (B-SW) transmission system is generally applied. However, the elastic Rayleigh backscattering noise severely degrades key performance after long fiber transmission. Here, the feasibility of a bidirectional wavelength division multiplexing (B-WDM) transmission in a single fiber for high-speed long-range PLSKD is verified, where the wavelength dependence of fiber channel reciprocity is evaluated. PLSKD based on B-WDM in one standard 100 GHz WDM channel is demonstrated, offering a key generation rate of 4.8 Gbps over a 200 km fiber link, providing a 200% increment in terms of key generation rate (KGR) compared with B-SW transmission.