BER performance analysis of 100 and 200 Gbit/s all-optical OTDM node using symmetric Mach-Zehnder switches

New insight to the feasibility of all-optical ultra speed switching up to 200 Gb/s. The technique will reduce the dependency and bottleneck on the electronic-to-optical-to-electronic conversion. Current conversion speed is up to 40 Gb/s in laboratories. The novel clock extraction technique proposed shows the potential of an all-optical switch. The research results are directly relevant to the access technology where optical fibre and RF is competing to be the solution. The growing demands of bandwidth will exceed RF capability while the optical fibre will be the optimum solution. A PhD project (Le-Minh) funded by the University Studentship, completed in 2007

Phase Modulation for Discrete-time Wiener Phase Noise Channels with Oversampling at High SNR

A discrete-time Wiener phase noise channel model is introduced in which multiple samples are available at the output for every input symbol. A lower bound on the capacity is developed. At high signal-to-noise ratio (SNR), if the number of samples per symbol grows with the square root of the SNR, the capacity pre-log is at least 3/4. This is strictly greater than the capacity pre-log of the Wiener phase noise channel with only one sample per symbol, which is 1/2. It is shown that amplitude modulation achieves a pre-log of 1/2 while phase modulation achieves a pre-log of at least 1/4.Comment: To appear in ISIT 201

Upper Bound on the Capacity of Discrete-Time Wiener Phase Noise Channels

A discrete-time Wiener phase noise channel with an integrate-and-dump multi-sample receiver is studied. An upper bound to the capacity with an average input power constraint is derived, and a high signal-to-noise ratio (SNR) analysis is performed. If the oversampling factor grows as $\text{SNR}^\alpha$ for $0\le \alpha \le 1$, then the capacity pre-log is at most $(1+\alpha)/2$ at high SNR.Comment: 5 pages, 1 figure. To be presented at IEEE Inf. Theory Workshop (ITW) 201

Capacity Outer Bound and Degrees of Freedom of Wiener Phase Noise Channels with Oversampling

The discrete-time Wiener phase noise channel with an integrate-and-dump multi-sample receiver is studied. A novel outer bound on the capacity with an average input power constraint is derived as a function of the oversampling factor. This outer bound yields the degrees of freedom for the scenario in which the oversampling factor grows with the transmit power $P$ as $P^{\alpha}$. The result shows, perhaps surprisingly, that the largest pre-log that can be attained with phase modulation at high signal-to-noise ratio is at most $1/4$.Comment: 5 pages, 1 figure, Submitted to Intern. Workshop Inf. Theory (ITW) 201

O-Band Differential Phase-Shift Quantum Key Distribution in 52-Channel C/L-Band Loaded Passive Optical Network

A cost-effective QKD transmitter is evaluated in a 16km reach, 2:16-split PON and yields 5.10-7secure bits/pulse. Co-existence with 20 down-and 1 upstream channel is possible at low QBER degradation of 0.93% and 1.1%

Considering Transmission Impairments in Wavelength Routed Networks

Abstract — We consider dynamically reconfigurable wavelength routed networks in which lightpaths carrying IP traffic are on demand established. We face the Routing and Wavelength Assignment problem considering as constraints the physical impairments that arise in all-optical wavelength routed networks. In particular, we study the impact of the physical layer when establishing a lightpath in transparent optical network. Because no signal transformation and regeneration at intermediate nodes occurs, noise and signal distortions due to non-ideal transmission devices are accumulated along the physical path, and they degrade the quality of the received signal. We propose a simple yet accurate model for the physical layer which consider both static and dynamic impairments, i.e., nonlinear effects depending on the actual wavelength/lightpath allocation. We then propose a novel algorithm to solve the RWA problem that explicitly considers the physical impairments. Simulation results show the effectiveness of our approach. Indeed, when the transmission impairments come into play, an accurate selection of paths and wavelengths which is driven by physical consideration is mandatory. I

Phase-coherent lightwave communications with frequency combs

Fiber-optical networks are a crucial telecommunication infrastructure in society. Wavelength division multiplexing allows for transmitting parallel data streams over the fiber bandwidth, and coherent detection enables the use of sophisticated modulation formats and electronic compensation of signal impairments. In the future, optical frequency combs may replace multiple lasers used for the different wavelength channels. We demonstrate two novel signal processing schemes that take advantage of the broadband phase coherence of optical frequency combs. This approach allows for a more efficient estimation and compensation of optical phase noise in coherent communication systems, which can significantly simplify the signal processing or increase the transmission performance. With further advances in space division multiplexing and chip-scale frequency comb sources, these findings pave the way for compact energy-efficient optical transceivers.Comment: 17 pages, 9 figure

Lower Bound on the Capacity of Continuous-Time Wiener Phase Noise Channels

A continuous-time Wiener phase noise channel with an integrate-and-dump multi-sample receiver is studied. A lower bound to the capacity with an average input power constraint is derived, and a high signal-to-noise ratio (SNR) analysis is performed. The capacity pre-log depends on the oversampling factor, and amplitude and phase modulation do not equally contribute to capacity at high SNR.Comment: Extended version of a paper submitted to ISIT 2015. 9 pages and 1 figure. arXiv admin note: text overlap with arXiv:1411.039

Security of Continuous Variable Quantum Cryptography

We discuss a quantum key distribution scheme in which small phase and amplitude modulations of CW light beams carry the key information. The presence of EPR type correlations provides the quantum protection. We identify universal constraints on the level of shared information between the intended receiver (Bob) and any eavesdropper (Eve) and use this to make a general evaluation of security. We identify teleportation as an optimum eavesdropping technique.Comment: 6 figure