Author
Reinhold Ludwig
Other affiliations: Fraunhofer Society
Bio: Reinhold Ludwig is an academic researcher from Heinrich Hertz Institute. The author has contributed to research in topics: Optical amplifier & Wavelength-division multiplexing. The author has an hindex of 40, co-authored 215 publications receiving 4938 citations. Previous affiliations of Reinhold Ludwig include Fraunhofer Society.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, the authors define general parameters that are of relevance for signal processing applications and show how basic experiments and general simulation procedures can be used to determine optimum operating conditions for the intended applications.
Abstract: Four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is an important tool for frequency conversion and fast optical switching in all-optical communication networks. We review the main applications of SOAs as nonlinear optical components. Concentrating on FWM, we define general parameters that are of relevance for signal processing applications. We show, how basic experiments and general simulation procedures can be used to determine optimum operating conditions for the intended applications. Besides a comprehensive investigation of FWM among continuous waves, we present new experimental results on FWM with picosecond optical pulses. A comparison of both reveals a different behavior and demonstrates that new optimization criteria and advanced theoretical models have to be applied for the case of short optical pulses. Moreover, we discuss the possibility to extract the dynamical SOA parameters from our experiments.
176 citations
TL;DR: By combining the techniques of optical TDM with polarisation multiplexing and DQPSK modulation format, 240 km transmission of 1.28 Tbit/s and 160 km transmission was performed in a single wavelength channel as mentioned in this paper.
Abstract: By combining the techniques of optical TDM with polarisation multiplexing and DQPSK modulation format, 240 km transmission of 1.28 Tbit/s and 160 km transmission of 2.56 Tbit/s has been performed in a single wavelength channel.
161 citations
TL;DR: In this article, the feasibility and limitations of optical data storage in a fiber loop optical buffer are studied theoretically and experimentally, a model of a fiber-loop buffer, incorporating semiconductor laser amplifiers (SLA) as switching gates, is described.
Abstract: Fiber loop optical buffers enable data storage for discrete time intervals and therefore appear suitable for applications in optical asynchronous transfer mode (OATM)-based networks where data are transmitted in cells of fixed length. In this paper, the feasibility and the limitations of optical data storage in a fiber loop optical buffer are studied theoretically and experimentally, A model of a fiber loop buffer, incorporating semiconductor laser amplifiers (SLA) as switching gates, is described. The two major interfering quantities are cross talk and amplified spontaneous emission of the SLA gates. To limit the impact of cross talk on the signal quality, an on/off ratio of the SLA gates of at least 30 dB is required. The paper describes the optimum operation conditions, which enable data storage for more than 100 circulations even for data rates in the range from 10 to 160 Gb/s.
141 citations
TL;DR: In this article, a review of ultra-high-speed data transmission in optical fibers based on optical time division multiplexing (OTDM) transmission technology is presented, where optical signal processing in the transmitter and receiver as well as the requirements on ultrahigh speed data transmission over a fiber link are discussed.
Abstract: This paper reviews ultrahigh-speed data transmission in optical fibers based on optical time division multiplexing (OTDM) transmission technology. Optical signal processing in the transmitter and receiver as well as the requirements on ultrahigh-speed data transmission over a fiber link are discussed. Finally, results of several OTDM-transmission experiments, including 160-Gb/s transmission over 4320 km, 1.28-Tb/s transmission over 240 km, and 2.56-Tb/s transmission over 160-km fiber link, are described
130 citations
TL;DR: In this paper, four-wave mixing based on ultrafast nonlinear gain dynamics in a semiconductor laser amplifier was applied for wavelength conversion of a 10-channel OFDM signal with a channel spacing of 9 GHz and a modulation rate of 140 Mb/s per channel.
Abstract: Four-wave-mixing based on ultrafast nonlinear gain dynamics in a semiconductor laser amplifier was applied for wavelength conversion of a 10-channel OFDM signal with a channel spacing of 9 GHz and a modulation rate of 140 Mb/s per channel. Conversion over 275 GHz was realised. BER measurements revealed no severe system degradation due to polarisation fluctuations or cross-talk. >
115 citations
Cited by
More filters
TL;DR: In this paper, the authors demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum, which provides new opportunities for increasing the data capacity of free-space optical communications links.
Abstract: Researchers demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the data capacity of free-space optical communications links.
3,556 citations
TL;DR: This work demonstrates a 32-Gbit’s−1 millimetre-wave link over 2.5 metres with a spectral efficiency of ~16 bit s− 1 Hz−1 using four independent orbital–angular momentum beams on each of two polarizations, and shows an 8-Gbits−1 link containing two orbital angular momentum beams with crosstalk less than −12.5 dB.
Abstract: One property of electromagnetic waves that has been recently explored is the ability to multiplex multiple beams, such that each beam has a unique helical phase front. The amount of phase front ‘twisting’ indicates the orbital angular momentum state number, and beams with different orbital angular momentum are orthogonal. Such orbital angular momentum based multiplexing can potentially increase the system capacity and spectral efficiency of millimetre-wave wireless communication links with a single aperture pair by transmitting multiple coaxial data streams. Here we demonstrate a 32-Gbit s−1 millimetre-wave link over 2.5 metres with a spectral efficiency of ~16 bit s−1 Hz−1 using four independent orbital–angular momentum beams on each of two polarizations. All eight orbital angular momentum channels are recovered with bit-error rates below 3.8 × 10−3. In addition, we demonstrate a millimetre-wave orbital angular momentum mode demultiplexer to demultiplex four orbital angular momentum channels with crosstalk less than −12.5 dB and show an 8-Gbit s−1 link containing two orbital angular momentum beams on each of two polarizations. High speed data transmission using orbital angular momentum beams has been recently demonstrated. Here, Yan et al. demonstrate a 32 Gbit/s millimetre-wave communication link using eight coaxially propagating independent orbital angular momentum beams with four orbital angular momentum states on two orthogonal polarizations.
1,002 citations
TL;DR: In this paper, the authors present a review of various wavelength conversion techniques, discusses the advantages and shortcomings of each technique, and addresses their implications for transparent WDM networks, and discuss their potential advantages over the optoelectronic counterpart.
Abstract: WDM networks make a very effective utilization of the fiber bandwidth and offer flexible interconnections based on wavelength routing. In high capacity, dynamic WDM networks, blocking due to wavelength contention can he reduced by wavelength conversion. Wavelength conversion addresses a number of key issues in WDM networks including transparency, interoperability, and network capacity. Strictly transparent networks offer seamless interconnections with full reconfigurability and interoperability. Wavelength conversion may be the first obstacle in realizing a transparent WDM network. Among numerous wavelength conversion techniques reported to date, only a few techniques offer strict transparency. Optoelectronic conversion (O/E-E/O) techniques achieve limited transparency, yet their mature technologies allow deployment in the near future. The majority of all-optical wavelength conversion techniques also offer limited transparency but they have a potential advantage over the optoelectronic counterpart in realizing lower packaging costs and crosstalk when multiple wavelength array configurations are considered. Wavelength conversion by difference-frequency generation offers a full range of transparency while adding no excess noise to the signal. Recent experiments showed promising results including a spectral inversion and a 90 nm conversion bandwidth. This paper reviews various wavelength conversion techniques, discusses the advantages and shortcomings of each technique, and addresses their implications for transparent networks.
928 citations
TL;DR: In this article, the noise and bit-error-rate characteristics of fiber-optic communication systems using semiconductor laser amplifiers are investigated theoretically and experimentally, and the dependence of system performance on amplifier characteristics such as optical bandwidth, noise figure, gain, etc., is shown.
Abstract: Fiber-optic communication systems using semiconductor laser amplifiers are investigated theoretically and experimentally. The noise and bit-error-rate characteristics of lightwave systems with optical amplifiers are calculated and the dependence of system performance on amplifier characteristics such as optical bandwidth, noise figure, gain, etc., is shown. Experimental results for both a 4-Gb/s optical preamplifier as well as coherent and direct detection systems with four inline amplifiers are presented. >
899 citations
TL;DR: In this article, the influence of saturation filtering on the bandwidth of the converters is explained and conditions for conversion at 20 Gb/s or more are identified for monolithic integrated interferometric wavelength converters.
Abstract: Following a brief introduction to the applications for wavelength conversion and the different available conversion techniques, the paper gives an in depth analysis of cross gain and cross phase wavelength conversion in semiconductor optical amplifiers. The influence of saturation filtering on the bandwidth of the converters is explained and conditions for conversion at 20 Gb/s or more are identified. The cross gain modulation scheme shows extinction ratio degradation for conversion to longer wavelengths. This can be overcome using cross phase modulation in semiconductor optical amplifiers that are integrated into interferometric structures. The first results for monolithic integrated interferometric wavelength converters are reviewed, and the quality of the converted signals is demonstrated by transmission of 10 Gb/s converted signals over 60 km of nondispersion shifted single mode fiber.
855 citations