Experimental Demonstration of Dual Polarization Nonlinear Frequency Division Multiplexed Optical Transmission System

Multi-eigenvalues transmission with information encoded simultaneously in both orthogonal polarizations is experimentally demonstrated. Performance below the HD-FEC limit is demonstrated for 8-bits/symbol 1-GBd signals after transmission up to 207 km of SSMF

A survey on fiber nonlinearity compensation for 400 Gbps and beyond optical communication systems

Optical communication systems represent the backbone of modern communication networks. Since their deployment, different fiber technologies have been used to deal with optical fiber impairments such as dispersion-shifted fibers and dispersion-compensation fibers. In recent years, thanks to the introduction of coherent detection based systems, fiber impairments can be mitigated using digital signal processing (DSP) algorithms. Coherent systems are used in the current 100 Gbps wavelength-division multiplexing (WDM) standard technology. They allow the increase of spectral efficiency by using multi-level modulation formats, and are combined with DSP techniques to combat the linear fiber distortions. In addition to linear impairments, the next generation 400 Gbps/1 Tbps WDM systems are also more affected by the fiber nonlinearity due to the Kerr effect. At high input power, the fiber nonlinear effects become more important and their compensation is required to improve the transmission performance. Several approaches have been proposed to deal with the fiber nonlinearity. In this paper, after a brief description of the Kerr-induced nonlinear effects, a survey on the fiber nonlinearity compensation (NLC) techniques is provided. We focus on the well-known NLC techniques and discuss their performance, as well as their implementation and complexity. An extension of the inter-subcarrier nonlinear interference canceler approach is also proposed. A performance evaluation of the well-known NLC techniques and the proposed approach is provided in the context of Nyquist and super-Nyquist superchannel systems.Comment: Accepted in the IEEE Communications Surveys and Tutorial

High-speed PAM4-based Optical SDM Interconnects with Directly Modulated Long-wavelength VCSEL

This paper reports the demonstration of high-speed PAM-4 transmission using a 1.5-{\mu}m single-mode vertical cavity surface emitting laser (SM-VCSEL) over multicore fiber with 7 cores over different distances. We have successfully generated up to 70 Gbaud 4-level pulse amplitude modulation (PAM-4) signals with a VCSEL in optical back-to-back, and transmitted 50 Gbaud PAM-4 signals over both 1-km dispersion-uncompensated and 10-km dispersion-compensated in each core, enabling a total data throughput of 700 Gbps over the 7-core fiber. Moreover, 56 Gbaud PAM-4 over 1-km has also been shown, whereby unfortunately not all cores provide the required 3.8 $\times$ 10 $^{-3}$ bit error rate (BER) for the 7% overhead-hard decision forward error correction (7% OH HDFEC). The limited bandwidth of the VCSEL and the adverse chromatic dispersion of the fiber are suppressed with pre-equalization based on accurate end-to-end channel characterizations. With a digital post-equalization, BER performance below the 7% OH-HDFEC limit is achieved over all cores. The demonstrated results show a great potential to realize high-capacity and compact short-reach optical interconnects for data centers.Comment: 7 pages, accepted to publication in 'Journal of Lightwave Technology (JLT

Advanced DSP Techniques for High-Capacity and Energy-Efficient Optical Fiber Communications

The rapid proliferation of the Internet has been driving communication networks closer and closer to their limits, while available bandwidth is disappearing due to an ever-increasing network load. Over the past decade, optical fiber communication technology has increased per fiber data rate from 10 Tb/s to exceeding 10 Pb/s. The major explosion came after the maturity of coherent detection and advanced digital signal processing (DSP). DSP has played a critical role in accommodating channel impairments mitigation, enabling advanced modulation formats for spectral efficiency transmission and realizing flexible bandwidth. This book aims to explore novel, advanced DSP techniques to enable multi-Tb/s/channel optical transmission to address pressing bandwidth and power-efficiency demands. It provides state-of-the-art advances and future perspectives of DSP as well

Quantum Cryptography

Quantum cryptography could well be the first application of quantum mechanics at the individual quanta level. The very fast progress in both theory and experiments over the recent years are reviewed, with emphasis on open questions and technological issues.Comment: 55 pages, 32 figures; to appear in Reviews of Modern Physic

Highly dispersive photonic crystal fibers for optical true time delay (TTD) based X-Band phased array antenna

textPhased array antenna (PAA) is a key component in many of the modern military and commercial radar and communication systems requiring highly directional beams with narrow beam widths. One of the advantages that this technology offers is a physical movement-free beam steering. Radar and communication technologies also require the PAA systems to be compact, light weight, demonstrate high bandwidth and electromagnetic interference (EMI) free performance. Conventional electrical phase shifters are inherently narrowband. This calls for technologies that have a larger bandwidth and high immunity to electromagnetic interference. Optical true-time-delay (TTD) technique is an emerging technology that is capable of providing these features along with the ability to provide frequency independent beam steering. Photonic crystal fiber (PCF) based optical TTD lines are capable of providing precise and continuous time delays required for PAA systems. Photonic crystal fibers are a new class of optical fibers with a periodic arrangement of air-holes around a core that can be designed to provide extraordinary optical characteristics which are unrealizable using conventional optical fibers. In this dissertation, highly dispersive photonic crystal fiber structures based on index-guidance and bandgap-guidance were designed. Designs exhibiting dispersion coefficients as large as -9500ps/nm/km and 4000ps/nm/km at 1550nm were presented. A TTD module utilizing a fabricated highly dispersive PCF with a dispersion coefficient of -600ps/nm/km at 1550nm was formed and characterized. The module consisted of 4 delay lines employing highly dispersive PCFs connected with various lengths of non-zero dispersion shifted fibers. By employing PCFs with enhanced dispersion coefficients, the TTD module size can be proportionally reduced. A 4-element linear X-band PAA system using the PCF-TTD module was formed and characterized to provide continuous time delays to steer radiofrequency (RF) beams from -41 degrees to 46 degrees by tuning the wavelength from 1530nm to 1560nm. Using the PCF-TTD based X-Band PAA system, single and simultaneous multiple beam transmission and reception capabilities were demonstrated. Noise and distortion performance characteristics of the entire PAA system were also evaluated and device control parameters were optimized to provide maximum spurious-free-dynamic range. In order to alleviate computational and weight requirements of practical large PAA systems, a sparse array instead of a standard array needs to be used. X-Band sparse array systems using PCF and dispersive fiber TTD technique were formed and RF beam steering was demonstrated. As an important achievement during the research work, the design and fabricated structure of a PCF currently reported to have the highest dispersion coefficient of -5400ps/nm/km at 1549nm, along with its limitations was also presented. Finally, other interesting applications of highly dispersive PCFs in the areas of pulse compression and soliton propagation were explored.Electrical and Computer Engineerin