381 research outputs found
Experimental Demonstration of Nonlinear Frequency Division Multiplexed Transmission
We experimentally demonstrate an NFDM optical system with modulation over
nonlinear discrete spectrum. Particularly, each symbol carries 4-bits from
multiplexing two eigenvalues modulated by QPSK constellation. We show a low
error performance using NFT detection with 4Gbps rate over 640km.Comment: Will be presented in ECOC 2015, Sept. 201
Information Transmission using the Nonlinear Fourier Transform, Part III: Spectrum Modulation
Motivated by the looming "capacity crunch" in fiber-optic networks,
information transmission over such systems is revisited. Among numerous
distortions, inter-channel interference in multiuser wavelength-division
multiplexing (WDM) is identified as the seemingly intractable factor limiting
the achievable rate at high launch power. However, this distortion and similar
ones arising from nonlinearity are primarily due to the use of methods suited
for linear systems, namely WDM and linear pulse-train transmission, for the
nonlinear optical channel. Exploiting the integrability of the nonlinear
Schr\"odinger (NLS) equation, a nonlinear frequency-division multiplexing
(NFDM) scheme is presented, which directly modulates non-interacting signal
degrees-of-freedom under NLS propagation. The main distinction between this and
previous methods is that NFDM is able to cope with the nonlinearity, and thus,
as the the signal power or transmission distance is increased, the new method
does not suffer from the deterministic cross-talk between signal components
which has degraded the performance of previous approaches. In this paper,
emphasis is placed on modulation of the discrete component of the nonlinear
Fourier transform of the signal and some simple examples of achievable spectral
efficiencies are provided.Comment: Updated version of IEEE Transactions on Information Theory, vol. 60,
no. 7, pp. 4346--4369, July, 201
Performance limits in optical communications due to fiber nonlinearity
In this paper, we review the historical evolution of predictions of the performance of optical communication systems. We will describe how such predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems
Optical Transmission Systems based on the Nonlinear Fourier Transformation
Solitons are stable pulse shapes, which propagate linearly and maintain their shape despite the highly nonlinear fiber optical channel. A challenge in the use of these signal pulses in optical data transmission is to multiplex them with high efficiency. One way to multiplex many solitons is the nonlinear Fourier transform (NFT). With the help of the NFT, signal spectra can be calculated which propagate linearly through a nonlinear channel. Thus, in perspective, it is possible to perform linear transmissions even in highly nonlinear regions with high signal power levels. The NFT decomposes a signal into a dispersive and a solitonic part. The dispersive part is similar to spectra of the conventional linear Fourier transform and dominates especially at low signal powers. As soon as the total power of a signal exceeds a certain limit, solitons arise. A disadvantage of solitons generated digitally by the NFT is their complex shape due to, for example, high electrical bandwidths or a poor peak-to-average power ratio. In the course of this work, a scalable system architecture of a photonic integrated circuit based on a silicon chip was designed, which allows to multiplex several simple solitons tightly together to push the complex electrical generation of higher order solitons into the optical domain. This photonic integrated circuit was subsequently designed and fabricated by the Institute of Integrated Photonics at RWTH Aachen University. Using this novel system architecture and additional equalization concepts designed in this work, soliton transmissions with up to four channels could be successfully realized over more than 5000 km with a very high spectral efficiency of 0.5 b/s/Hz in the soliton range
Digital signal processing for fiber nonlinearities [Invited]
This paper reviews digital signal processing techniques that compensate, mitigate, and exploit fiber nonlinearities in coherent optical fiber transmission systems
Slice-Less Optical Arbitrary Waveform Measurement (OAWM) in a Bandwidth of More than 600 GHz Using Soliton Microcombs
We propose and demonstrate a novel scheme for optical arbitrary waveform
measurement (OAWM) that exploits chip-scale Kerr soliton combs as highly
scalable multiwavelength local oscillators (LO) for ultra-broadband full-field
waveform acquisition. In contrast to earlier concepts, our approach does not
require any optical slicing filters and thus lends itself to efficient
implementation on state-of-the-art high-index-contrast integration platforms
such as silicon photonics. The scheme allows to measure truly arbitrary
waveforms with high accuracy, based on a dedicated system model which is
calibrated by means of a femtosecond laser with known pulse shape. We
demonstrated the viability of the approach in a proof-of-concept experiment by
capturing an optical waveform that contains multiple 16 QAM and 64 QAM
wavelength-division multiplexed (WDM) data signals with symbol rates of up to
80 GBd, reaching overall line rates of up to 1.92 Tbit/s within an optical
acquisition bandwidth of 610 GHz. To the best of our knowledge, this is the
highest bandwidth that has so far been demonstrated in an OAWM experiment
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
Demonstration of nonlinear inverse synthesis transmission over transoceanic distances
Nonlinear Fourier transform (NFT) and eigenvalue communication with the use of nonlinear signal spectrum (both discrete and continuous), have been recently discussed as promising transmission methods to combat fiber nonlinearity impairments. In this paper, for the first time, we demonstrate the generation, detection and transmission performance over transoceanic distances of 10 Gbaud and nonlinear inverse synthesis (NIS) based signal (4 Gb/s line rate), in which the transmitted information is encoded directly onto the continuous part of the signal nonlinear spectrum. By applying effective digital signal processing techniques, a reach of 7344 km was achieved with a bit-error-rate (BER) (2.1Ă—10-2) below the 20% FEC threshold. This represents an improvement by a factor of ~12 in data capacity x distance product compared with other previously demonstrated NFT-based systems, showing a significant advance in the active research area of NFT-based communication systems
Chip-scale optical frequency comb sources for terabit communications
The number of devices connected to the internet and the required data transmission speeds are increasing exponentially. To keep up with this trend, data center interconnects should scale up to provide multi-Tbit/s connectivity. With typical distances from a few kilometers to 100 km, these links require the use of a high number of WDM channels. The associated transceivers should have low cost and footprint. The scalability of the number of channels, however, is still limited by the lack of adequate optical sources.
In this book, we investigate novel chip-scale frequency comb generators as multi-wavelength light sources in WDM links. With a holistic model, we estimate the performance of comb-based WDM links, and we compare the transmission performance of different comb generator types, namely a quantum-dash mode-locked laser diode and a microresonator-based Kerr comb generator. We characterize their potential for massively-parallel WDM transmission with various transmission experiments. Combined with photonic integrated circuits, these comb sources offer a path towards highly scalable, compact, and energy-efficient Tbit/s transceivers
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