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ABSTRACT: We investigate the performance and DSP resource requirements of digitally generated OFDM and sinc-shaped Nyquist pulses. The two multiplexing techniques are of interest as they offer highest spectral efficiency. The comparison aims at determining which technology performs better with limited processing capacities of state-of-the-art FPGAs. It is shown that a novel Nyquist pulse shaping technique, based on look-up tables requires lower resource count than equivalent IFFT-based OFDM signal generation while achieving similar performance with low inter-channel guard-bands in ultra-dense WDM. Our findings are based on a resource assessment of selected DSP implementations in terms of both simulations and experimental validations. The experiments were performed with real-time software-defined transmitters using a single or three optical carriers.
Optics Express 12/2012; 20(26):B543-51. · 3.59 Impact Factor
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ABSTRACT: Modulation cancellation and signal inversion are demonstrated within reflective semiconductor optical amplifiers. The effect is necessary to implement colorless optical network units for network end-users, where downstream signals need to be erased in order to reuse the carrier for upstream transmission. The results presented here indicate that reflective semiconductor optical amplifiers possess the perfect high-speed all-optical gain saturation characteristics to completely cancel the downstream modulation at microwatt optical power levels and are thus the prime candidate to be constituents of future optical network units. Theoretical considerations are supported by experiments that show the cancellation of signals with a 6 dB extinction ratio at 2.5 Gbit/s.
Optics Express 12/2012; 20(26):B587-94. · 3.59 Impact Factor
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ABSTRACT: This paper presents a real-time, coherent optical OFDM transmitter based on a field programmable gate array implementation. The transmitter uses 16QAM mapping and runs at 28 GSa/s achieving a data rate of 85.4 Gb/s on a single polarization. A cyclic prefix of 25% of the symbol duration is added enabling dispersion-tolerant transmission over up to 400 km of SSMF. This is the first transmission experiment performed with a real-time OFDM transmitter running at data rates higher than 40 Gb/s. A key aspect of the paper is the introduction of a novel method for OFDM symbol synchronization without relying on training symbols. Unlike conventional preamble-based synchronization methods which perform cross-correlations at regular time intervals and let the system run freely in between, the proposed method performs synchronization in a continuous manner ensuring correct symbol alignment at all times.
Optics Express 09/2012; 20(19):21612-7. · 3.59 Impact Factor
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ABSTRACT: We describe a concept for second-order nonlinear optical processes in silicon photonics. A silicon-organic hybrid (SOH) double slot waveguide is dispersion-engineered for mode phase-matching (MPM). The proposed waveguide enables highly efficient nonlinear processes in the mid-IR range. With a cladding nonlinearity of χ<sup>(2)</sup> = 230 pm/V and 20 dBm pump power at a CW wavelength of 1550 nm, we predict a gain of 14.7 dB/cm for a 3100 nm signal. The suggested structure enables for the first time efficient second-order nonlinear optical mixing in silicon photonics with standard technology.
Optics Express 08/2012; 20(18):20506-15. · 3.59 Impact Factor
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ABSTRACT: Photonic integration requires a versatile packaging technology that enables low-loss interconnects between photonic chips in three-dimensional configurations. In this paper we introduce the concept of photonic wire bonding, where polymer waveguides with three-dimensional freeform geometries are used to bridge the gap between nanophotonic circuits located on different chips. In a proof-of-principle experiment, we demonstrate the fabrication of single-mode photonic wire bonds (PWB) by direct-write two-photon lithography. First-generation prototypes allow for efficient broadband coupling with average insertion losses of only 1.6 dB in the C-band and can carry wavelength-division multiplexing signals with multi-Tbit/s data rates. Photonic wire bonding is well suited for automated mass production, and we expect the technology to enable optical multi-chip systems with enhanced performance and flexibility.
Optics Express 07/2012; 20(16):17667-77. · 3.59 Impact Factor
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R Bonk,
G Huber,
T Vallaitis,
S Koenig,
R Schmogrow,
D Hillerkuss,
R Brenot,
F Lelarge,
G-H Duan,
S Sygletos,
C Koos,
W Freude, J Leuthold
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ABSTRACT: The capability of semiconductor optical amplifiers (SOA) to amplify advanced optical modulation format signals is investigated. The input power dynamic range is studied and especially the impact of the SOA alpha factor is addressed. Our results show that the advantage of a lower alpha-factor SOA decreases for higher-order modulation formats. Experiments at 20 GBd BPSK, QPSK and 16QAM with two SOAs with different alpha factors are performed. Simulations for various modulation formats support the experimental findings.
Optics Express 04/2012; 20(9):9657-72. · 3.59 Impact Factor
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R Schmogrow,
D Hillerkuss,
S Wolf,
B Bäuerle,
M Winter,
P Kleinow,
B Nebendahl,
T Dippon,
P C Schindler,
C Koos,
W Freude, J Leuthold
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ABSTRACT: We demonstrate for the first time transmission of 54 Gbit/s and 48 Gbit/s over 44 km and 150 km, respectively, utilizing an optical bandwidth of only 3 GHz. We used polarization division multiplexed 512QAM and 256QAM modulation formats in combination with Nyquist pulse shaping having virtually zero roll-off. The resulting spectral efficiencies range up to 18 bit/s/Hz and 16 bit/s/Hz, respectively. Taking into account the overhead required for forward error correction, the occupied signal bandwidth corresponds to net spectral efficiencies of 14.4 bit/s/Hz and 15 bit/s/Hz, which could be achieved in a wavelength division multiplexed network without spectral guard bands.
Optics Express 03/2012; 20(6):6439-47. · 3.59 Impact Factor
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R. Schmogrow,
B. Nebendahl,
M. Winter,
A. Josten,
D. Hillerkuss,
S. Koenig,
J. Meyer,
M. Dreschmann,
M. Huebner,
C. Koos,
J. Becker,
W. Freude, J. Leuthold
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ABSTRACT: We examine the relation between optical signal-to-noise ratio (OSNR), error vector magnitude (EVM), and bit-error ratio (BER). Theoretical results and numerical simulations are compared to measured values of OSNR, EVM, and BER. We conclude that the EVM is an appropriate metric for optical channels limited by additive white Gaussian noise. Results are supported by experiments with six modulation formats at symbol rates of 20 and 25 GBd generated by a software-defined transmitter.
IEEE Photonics Technology Letters 02/2012; · 2.19 Impact Factor
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R Schmogrow,
M Winter,
M Meyer,
D Hillerkuss,
S Wolf,
B Baeuerle,
A Ludwig,
B Nebendahl,
S Ben-Ezra,
J Meyer,
M Dreschmann,
M Huebner,
J Becker,
C Koos,
W Freude, J Leuthold
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ABSTRACT: Nyquist sinc-pulse shaping provides spectral efficiencies close to the theoretical limit. In this paper we discuss the analogy to optical orthogonal frequency division multiplexing and compare both techniques with respect to spectral efficiency and peak to average power ratio. We then show that using appropriate algorithms, Nyquist pulse shaped modulation formats can be encoded on a single wavelength at speeds beyond 100 Gbit/s in real-time. Finally we discuss the proper reception of Nyquist pulses.
Optics Express 01/2012; 20(1):317-37. · 3.59 Impact Factor
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Computing, Networking and Communications (ICNC), 2012 International Conference on; 01/2012
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ABSTRACT: Photonic wire bonds (PWB) enable single-mode chip-to-chip interconnects that are suitable for mass production. We demonstrate for the first time a single-mode PWB link between two different nanophotonic silicon-on-insulator chips.
Group IV Photonics (GFP), 2011 8th IEEE International Conference on; 10/2011
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C. Koos,
L. Alloatti,
D. Korn,
R. Palmer,
T. Vallaitis,
R. Bonk,
D. Hillerkuss,
J. Li,
W. Bogaerts,
P. Dumon,
R. Baets,
M.L. Scimeca,
I. Biaggio,
A. Barklund,
R. Dinu,
J. Wieland,
M. Fournier,
J. Fedeli,
W. Freude, J. Leuthold
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ABSTRACT: Silicon nanophotonics is considered a key enabler of future photonic-electronic information processing systems. Driven by substantial research investments, photonic integration on silicon-on-insulator (SOI) substrates has reached a degree of maturity that already permits industrial adoption. Silicon-organic hybrid integration (SOH) is a viable extension of the SOI material system for efficient electro-optic modulation and ultrafast all-optical signal processing.
General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
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R Schmogrow,
M Winter,
D Hillerkuss,
B Nebendahl,
S Ben-Ezra,
J Meyer,
M Dreschmann,
M Huebner,
J Becker,
C Koos,
W Freude, J Leuthold
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ABSTRACT: Real-time OFDM transmitters breaking the 100 Gbit/s barrier require high-performance, usually FPGA-based digital signal processing. Especially the Fourier transform as a key operation of any OFDM system must be optimized with respect to performance and chip area utilization. Here, we demonstrate an alternative to the widely adopted fast Fourier transform algorithm. Based on an extensive yet optimized use of pre-set look-up tables, our FPGA implementation supports fast reconfigurable channel equalization and switching times in the nanosecond range without re-loading any code. We demonstrate the potential of the concept by realizing the first real-time single polarization OFDM transmitter generating a 101.5 Gbit/s data stream by modulating 58 subcarriers with 16QAM.
Optics Express 06/2011; 19(13):12740-9. · 3.59 Impact Factor
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ABSTRACT: When silicon strip and slot waveguides are coated with a 50 nm amorphous titanium dioxide (TiO2) film, measured losses at a wavelength of 1.55 μm can be as low as (2 ± 1)dB/cm and (7 ± 2)dB/cm, respectively. We use atomic layer deposition (ALD), estimate the effect of ALD growth on the surface roughness, and discuss the effect on the scattering losses. Because the gap between the rails of a slot waveguide narrows by the TiO2 deposition, the effective slot width can be back-end controlled. This is useful for precise adjustment if the slot is to be filled with, e. g., a nonlinear organic material or with a sensitizer for sensors applications.
Optics Express 06/2011; 19(12):11529-38. · 3.59 Impact Factor
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L Alloatti,
D Korn,
R Palmer,
D Hillerkuss,
J Li,
A Barklund,
R Dinu,
J Wieland,
M Fournier,
J Fedeli,
H Yu,
W Bogaerts,
P Dumon,
R Baets,
C Koos,
W Freude, J Leuthold
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ABSTRACT: CMOS-compatible optical modulators are key components for future silicon-based photonic transceivers. However, achieving low modulation voltage and high speed operation still remains a challenge. As a possible solution, the silicon-organic hybrid (SOH) platform has been proposed. In the SOH approach the optical signal is guided by a silicon waveguide while the electro-optic effect is provided by an organic cladding with a high χ(2)-nonlinearity. In these modulators the optical nonlinear region needs to be connected to the modulating electrical source. This requires electrodes, which are both optically transparent and electrically highly conductive. To this end we introduce a highly conductive electron accumulation layer which is induced by an external DC "gate" voltage. As opposed to doping, the electron mobility is not impaired by impurity scattering. This way we demonstrate for the first time data encoding with an SOH electro-optic modulator. Using a first-generation device at a data-rate of 42.7 Gbit/s, widely open eye diagrams were recorded. The measured frequency response suggests that significantly larger data rates are feasible.
Optics Express 06/2011; 19(12):11841-51. · 3.59 Impact Factor
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D. Hillerkuss,
R. Schmogrow,
T. Schellinger,
M. Jordan,
M. Winter,
G. Huber,
T. Vallaitis,
R. Bonk,
P. Kleinow,
F. Frey, [......],
A. Oehler,
K. Weingarten,
T. Ellermeyer,
J. Lutz,
M. Moeller,
M. Huebner,
J. Becker,
C. Koos,
W. Freude, J. Leuthold
Nature Photonics 05/2011; 5(6):364-371. · 29.28 Impact Factor
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D. Hillerkuss,
R. Schmogrow,
T. Schellinger,
M. Jordan,
M. Winter,
G. Huber,
T. Vallaitis,
R. Bonk,
P. Kleinow,
F. Frey, [......],
A. Oehler,
K. Weingarten,
T. Ellermeyer,
J. Lutz,
M. Moeller,
M. Huebner,
J. Becker,
C. Koos,
W. Freude, J. Leuthold
Nature Photonics. 05/2011; 5:364.
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A Melikyan,
N Lindenmann,
S Walheim,
P M Leufke,
S Ulrich,
J Ye,
P Vincze,
H Hahn,
Th Schimmel,
C Koos,
W Freude, J Leuthold
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ABSTRACT: An electrically controlled ultra-compact surface plasmon polariton absorption modulator (SPPAM) is proposed. The device can be as small as a few micrometers depending on the required extinction ratio and the acceptable loss. The device allows for operation far beyond 100 Gbit/s, being only limited by RC time constants. The absorption modulator comprises a stack of metal/insulator/metal-oxide/metal layers, which support a strongly confined asymmetric surface plasmon polariton (SPP) in the 1.55 μm telecommunication wavelength window. Absorption modulation is achieved by electrically modulating the free carrier density in the intermediate metal-oxide layer. The concept is supported by proof-of-principle experiments.
Optics Express 04/2011; 19(9):8855-69. · 3.59 Impact Factor
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R. Bonk,
P. Vorreau,
D. Hillerkuss,
W. Freude,
G. Zarris,
D. Simeonidou,
F. Parmigiani,
P. Petropoulos,
R. Weerasuriya,
S. Ibrahim,
A. Ellis,
D. Klonidis,
I. Tomkos, J. Leuthold
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ABSTRACT: A regenerative all-optical grooming switch for interconnecting 130 Gbit/s on-off keying (OOK) metro/core ring and 43 Gbit/s-OOK metro/access ring networks with switching functionality in time, space, and wavelength domains is demonstrated. Key functionalities of the switch are traffic aggregation with time-slot interchanging functionality, optical time division multiplexing (OTDM) to wavelength division multiplexing (WDM) demultiplexing, and multi-wavelength 2R regeneration. Laboratory and field demonstrations show the excellent performance of the new concept with error-free signal transmission and Q-factors above 20 dB.
Journal of Optical Communications and Networking 04/2011; · 1.87 Impact Factor
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ABSTRACT: Impact of SOA α-factor on dynamic range limitation decreases for higher-order modulation formats leading to undistinguishable performances of bulk and QD SOAs. Results are supported by experiments at 20 GBd BPSK, QPSK and 16-QAM.
Optical Fiber Communication Conference and Exposition (OFC/NFOEC), 2011 and the National Fiber Optic Engineers Conference; 01/2011
