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Berthold Lankl

Bio: Berthold Lankl is an academic researcher from Bundeswehr University Munich. The author has contributed to research in topics: Phase-shift keying & MIMO. The author has an hindex of 15, co-authored 60 publications receiving 1063 citations.


Papers
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Journal ArticleDOI
TL;DR: This paper presents a new and fast algorithm to perform blind adaptive CD compensation through frequency-domain equalization and proposes an XPM-mitigating carrier phase recovery as an extension of the standard Viterbi-Viterbi algorithm.
Abstract: In this paper, we outline the design of signal processing (DSP) algorithms with blind estimation for 100-G coherent optical polarization-diversity receivers in single-carrier systems. As main degrading optical propagation effects, we considered chromatic dispersion (CD), polarization-mode dispersion (PMD), polarization-dependent loss (PDL), and cross-phase modulation (XPM). In the context of this work, we developed algorithms to increase the robustness of the single DSP receiver modules against the aforesaid propagation effects. In particular, we first present a new and fast algorithm to perform blind adaptive CD compensation through frequency-domain equalization. This low complexity equalizer component inherits a highly precise estimation of residual dispersion independent from previous or subsequent blocks. Next, we introduce an original dispersion-tolerant timing recovery and illustrate the derivation of blind polarization demultiplexing, capable to operate also in condition of high PDL. At last, we propose an XPM-mitigating carrier phase recovery as an extension of the standard Viterbi-Viterbi algorithm.

316 citations

Journal ArticleDOI
TL;DR: In this paper, a method for combined fiber parameter estimation from digital filter coefficients of a polarization diverse coherent receiver is presented, where all deterministic linear optical channel parameters like residual chromatic dispersion (CD), polarization-mode dispersion, and polarization dependent loss (PDL) are continuously monitored by analysis of the filter impulse response of the adaptive equalizer.
Abstract: In this paper, we present a method for combined fiber parameter estimation from digital filter coefficients of a polarization diverse coherent receiver. All deterministic linear optical channel parameters like residual chromatic dispersion (CD), polarization-mode dispersion (PMD), and polarization-dependent loss (PDL) are continuously monitored by analysis of the filter impulse response of the adaptive equalizer. After deriving the according equations from the theoretical linear fiber channel model, we demonstrate robust estimation for a joint combination of all impairments.

161 citations

Proceedings ArticleDOI
22 Mar 2009
TL;DR: A novel low complexity estimation algorithm precisely estimates arbitrarily large dispersion in a fixed adaptation length in blind adaptive chromatic dispersion equalization for coherent polarization multiplexed (NRZ/RZ)-QPSK receivers.
Abstract: Blind adaptive chromatic dispersion equalization for coherent polarization multiplexed (NRZ/RZ)-QPSK receivers is presented. A novel low complexity estimation algorithm precisely estimates arbitrarily large dispersion in a fixed adaptation length.

76 citations

Proceedings ArticleDOI
22 Dec 2008
TL;DR: In this article, the feasibility of 100G overlaying existing 10G/40G commercial systems is demonstrated, showing that 100G can be achieved over a 50GHz grid over 1,040 km field fiber and two ROADMs.
Abstract: 111-Gb/s transmission combined with 2 times 43-Gb/s and 8 times 10.7-Gb/s on a 50-GHz grid over 1,040-km field fiber and two ROADMs is demonstrated, showing the feasibility of 100G overlaying existing 10G/40G commercial systems.

50 citations

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate transmission of a 111-Gb/s coherent polarization-multiplexed return-to-zero differential quadrature phase shift keying signal over 1040-km field-deployed fiber together with different types of neighboring channels, and with a cascade of 50-GHz reconfigerable optical add-drop multiplexers.
Abstract: We demonstrate transmission of a 111-Gb/s coherent polarization-multiplexed return-to-zero differential quadrature phase-shift keying signal over 1040-km field-deployed fiber together with different types of neighboring channels, and with a cascade of 50-GHz reconfigerable optical add-drop multiplexers. Our transmission experiment proves the feasibility of transmitting a 111-Gb/s phase-modulated channel with 10 times 10.7-Gb/s on-off keying neighboring channels on a 50-GHz grid, despite the presence of strong cross-phase modulation.

44 citations


Cited by
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Journal ArticleDOI
TL;DR: An up-to-date survey on FSO communication systems is presented, describing FSO channel models and transmitter/receiver structures and details on information theoretical limits of FSO channels and algorithmic-level system design research activities to approach these limits are provided.
Abstract: Optical wireless communication (OWC) refers to transmission in unguided propagation media through the use of optical carriers, i.e., visible, infrared (IR), and ultraviolet (UV) bands. In this survey, we focus on outdoor terrestrial OWC links which operate in near IR band. These are widely referred to as free space optical (FSO) communication in the literature. FSO systems are used for high rate communication between two fixed points over distances up to several kilometers. In comparison to radio-frequency (RF) counterparts, FSO links have a very high optical bandwidth available, allowing much higher data rates. They are appealing for a wide range of applications such as metropolitan area network (MAN) extension, local area network (LAN)-to-LAN connectivity, fiber back-up, backhaul for wireless cellular networks, disaster recovery, high definition TV and medical image/video transmission, wireless video surveillance/monitoring, and quantum key distribution among others. Despite the major advantages of FSO technology and variety of its application areas, its widespread use has been hampered by its rather disappointing link reliability particularly in long ranges due to atmospheric turbulence-induced fading and sensitivity to weather conditions. In the last five years or so, there has been a surge of interest in FSO research to address these major technical challenges. Several innovative physical layer concepts, originally introduced in the context of RF systems, such as multiple-input multiple-output communication, cooperative diversity, and adaptive transmission have been recently explored for the design of next generation FSO systems. In this paper, we present an up-to-date survey on FSO communication systems. The first part describes FSO channel models and transmitter/receiver structures. In the second part, we provide details on information theoretical limits of FSO channels and algorithmic-level system design research activities to approach these limits. Specific topics include advances in modulation, channel coding, spatial/cooperative diversity techniques, adaptive transmission, and hybrid RF/FSO systems.

1,749 citations

Journal ArticleDOI
TL;DR: In this article, a theoretical analysis of the dual-polarization constant modulus algorithm is presented, where the control surfaces several different equalizer algorithms are derived, including the decision-directed, trained, and the radially directed equalizer for both polarization division multiplexed quadriphase shift keyed (PDM-QPSK) and 16 level quadrature amplitude modulation (PDm-16-QAM).
Abstract: Digital coherent receivers have caused a revolution in the design of optical transmission systems, due to the subsystems and algorithms embedded within such a receiver. After giving a high-level overview of the subsystems, the optical front end, the analog-to-digital converter (ADC) and the digital signal processing (DSP) algorithms, which relax the tolerances on these subsystems are discussed. Attention is then turned to the compensation of transmission impairments, both static and dynamic. The discussion of dynamic-channel equalization, which forms a significant part of the paper, includes a theoretical analysis of the dual-polarization constant modulus algorithm, where the control surfaces several different equalizer algorithms are derived, including the constant modulus, decision-directed, trained, and the radially directed equalizer for both polarization division multiplexed quadriphase shift keyed (PDM-QPSK) and 16 level quadrature amplitude modulation (PDM-16-QAM). Synchronization algorithms employed to recover the timing and carrier phase information are then examined, after which the data may be recovered. The paper concludes with a discussion of the challenges for future coherent optical transmission systems.

772 citations

Journal ArticleDOI
TL;DR: Focusing on the optical transport and switching layer, aspects of large-scale spatial multiplexing, massive opto-electronic arrays and holistic optics-electronics-DSP integration, as well as optical node architectures for switching and multiplexed of spatial and spectral superchannels are covered.
Abstract: Celebrating the 20th anniversary of Optics Express, this paper reviews the evolution of optical fiber communication systems, and through a look at the previous 20 years attempts to extrapolate fiber-optic technology needs and potential solution paths over the coming 20 years. Well aware that 20-year extrapolations are inherently associated with great uncertainties, we still hope that taking a significantly longer-term view than most texts in this field will provide the reader with a broader perspective and will encourage the much needed out-of-the-box thinking to solve the very significant technology scaling problems ahead of us. Focusing on the optical transport and switching layer, we cover aspects of large-scale spatial multiplexing, massive opto-electronic arrays and holistic optics-electronics-DSP integration, as well as optical node architectures for switching and multiplexing of spatial and spectral superchannels.

498 citations

Journal ArticleDOI
Steven Gringeri1, B. Basch1, Vishnu Shukla1, R. Egorov1, Tiejun J. Xia1 
TL;DR: The architectures and various ROADM implementations including colorless, directionless, and contentionless add/drop structures are presented and the effect of scaling bit rates beyond 100 Gb/s onROADM architectures is reviewed including providing variable channel bandwidth depending on bit rate.
Abstract: Flexibility to support mesh topologies, dynamic capacity allocation, and automated network control and light path setup are key elements in the design of next-generation optical transport networks. To realize these capabilities, reconfigurable optical add/drop multiplexers with dynamic add/drop structures, embedded control planes, and lightpath characterization are required. This article presents the architectures and various ROADM implementations including colorless, directionless, and contentionless add/drop structures. The effect of scaling bit rates beyond 100 Gb/s on ROADM architectures is reviewed including providing variable channel bandwidth depending on bit rate. Automated provisioning and restoration using the GMPLS control plane and optical measurement approaches for lightpaths are also discussed.

484 citations