Quantum communications is an emerging field with many promising applications. Its usefulness and range of
applicability in optical fiber will depend strongly on the extent to which quantum channels can be reliably transported
over transparent reconfigurable optical networks, rather than being limited to dedicated point-to-point links. This
presents a number of challenges, particularly when single-photon quantum and much higher power classical optical
signals are combined onto a single physical infrastructure to take advantage of telecom networks built to carry
conventional traffic. In this paper, we report on experimental demonstrations of successful quantum key distribution
(QKD) in this complex environment, and on measurements of physical-layer impairments, including Raman scattering
from classical optical channels, which can limit QKD performance. We then extend the analysis using analytical models
incorporating impairments, to investigate QKD performance while multiplexed with conventional data channels at other
wavelengths. Finally, we discuss the implications of these results for evaluating the most promising domains of use for
QKD in real-world optical networks.
Quantum communications is fast becoming an important component of many applications in quantum information
science. Sharing quantum information over a distance among geographically separated nodes using photonic qubits
requires a reconfigurable transparent networking infrastructure that can support quantum information services. Using
quantum key distribution (QKD) as an example of a quantum communications service, we investigate the ability of fiber
networks to support both conventional optical traffic and single-photon quantum communications signals on a shared
infrastructure. The effect of Raman scattering from conventional channels on the quantum bit error rate (QBER) of a
QKD system is analyzed. Additionally, the potential impact and mitigation strategies of other transmission impairments
such as four-wave mixing, cross-phase modulation, and noise from mid-span optical amplifiers are discussed. We also
review recent trends toward the development of automated and integrated QKD systems which are important steps
toward reliable and manufacturable quantum communications systems.
We experimentally analyze power excursions on a surviving data channel due to praseodymium-doped fluoride fiber amplifier (PDFFA) gain transients. These transients are a result of the equivalent time-varying power for adding or dropping up to 15 wavelength division multiplexed (WDM) signals from a 16-channel WDM system at 1310 nm. We find that power excursions for the surviving 10-Gbit/s data channel increase with an increase in the number of channels added or dropped from the system. Bit error rate (BER) measurements on the surviving channel indicate that a power penalty of up to 3.5 dB as compared to the steady-state condition results from a 15-channel add-drop event. These results provide indication of the applicability of PDFFA amplification to dynamic reconfigurable optical networks in future DWDM systems that incorporate wavelengths in the 1310-nm region.
A novel, user-friendly quantum key distribution (QKD) system operating at a wavelength of 1550nm and at a clock rate of 10MHz was constructed to explore the compatibility of this emerging technology with the optical fiber network environment. Custom circuit boards providing the low-level control and sensing functions for both the transmitter and receiver were developed, allowing software-based system reconfiguration via USB interface to personal computers. The computer control allowed the user to change operating parameters such as detector bias voltages and pulse delays and also allowed for self-tuning of the system. Epitaxx avalanche photodiodes, operated in Geiger mode, were used to detect the single photons. A complete QKD protocol stack incorporating the "sifting", reconciliation, privacy amplification, authentication and key confirmation functions was implemented in software. The system was tested over twenty five kilometers of dark underground fiber, producing 18.6 million sifted bits, with a sifted bit error rate of 4.9% at an average number of photons per pulse of 0.2, during a continuous 12-hour period of self-sustaining operation: a small portion of the secret bits distilled from each session's sifted bits were used to authenticate the next session. A total of 6.8 million shared secret bits were produced.
Quantum key distribution (QKD) is an emerging technology for secure distribution of keys between users linked by free-space or fiber optic transmission facilities. QKD has usually been designed for and operated over dedicated point-to-point links. However, the commercial world has been developing increasingly sophisticated fiber networks, with basic networking functions such as routing and multiplexing performed in the optical domain. One of the most important practical questions for the future of QKD is to what extent it can benefit from these trends, either to expand the capabilities of dedicated quantum networks, or to avoid the need for dedicated networks by combining quantum and conventional optical signals onto a single infrastructure.
In this paper, we report on systematic investigations of these issues using a 1310-nm weak-coherent, phase-encoded B92 prototype QKD system developed by Los Alamos that includes the implementation of error correction, privacy amplification, and authentication. We have demonstrated reconfigurability of QKD networks via optical switching and successful QKD operation in the presence of amplified DWDM signals over 10 km of fiber. We have identified anti-Stokes Raman scattering of the DWDM signals in the fiber as a dominant transmission impairment for QKD, and developed filtering architectures to extend transmission distances to at least 25 km. We have also measured noise backgrounds and polarization variations in network fibers to understand applicability to real-world networks. We will discuss the implications of our results for the choice of QKD wavelengths, wavelength-spacing between QKD and conventional channels, and QKD network architectures.
To increase the transmission capacity of future communication networks is becoming very critical. This task can only be accomplished by taking advantage of optical networks where multiplexing techniques such as Dense Wavelength Division Multiplexing and Optical Time Division Multiplexing are employed. To avoid electronic bottlenecks a whole new generation of ultrafast devices is needed. To fulfill these needs a new class of all optical devices has been proposed and developed. By taking advantage of the nonlinear dynamics the semiconductor optical amplifiers in combination with the fiber interferometers a new generation of ultrafast all-optical demultiplexers and wavelength converters has been demonstrated. Newly developed broadband optical fiber, a new generation of fiber amplifiers, and extensive progress in dispersion management has helped substantially to increase bitrates and transmission distances in the current optical networks. The latest technologies in the area of micro-machining have created very attractive low cost MEMS. Recently announced use of bubble technology for all-optical switching might also lead to the development of next generation large scale switching fabrics. In this paper we discuss progress and new trends in some of these areas.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.