138 research outputs found
Adaptive Wavelet Collocation Method for Simulation of Time Dependent Maxwell's Equations
This paper investigates an adaptive wavelet collocation time domain method
for the numerical solution of Maxwell's equations. In this method a
computational grid is dynamically adapted at each time step by using the
wavelet decomposition of the field at that time instant. In the regions where
the fields are highly localized, the method assigns more grid points; and in
the regions where the fields are sparse, there will be less grid points. On the
adapted grid, update schemes with high spatial order and explicit time stepping
are formulated. The method has high compression rate, which substantially
reduces the computational cost allowing efficient use of computational
resources. This adaptive wavelet collocation method is especially suitable for
simulation of guided-wave optical devices
3D-Printed Optics for Wafer-Scale Probing
Mass production of photonic integrated circuits requires high-throughput
wafer-level testing. We demonstrate that optical probes equipped with
3D-printed elements allow for efficient coupling of light to etched facets of
nanophotonic waveguides. The technique is widely applicable to different
integration platforms.Comment: Accepted for presentation at European Conference on Optical
Communications (ECOC) 201
Coherent modulation up to 100 GBd 16QAM using silicon-organic hybrid (SOH) devices
We demonstrate the generation of higher-order modulation formats using
silicon-based inphase/quadrature (IQ) modulators at symbol rates of up to 100
GBd. Our devices exploit the advantages of silicon-organic hybrid (SOH)
integration, which combines silicon-on-insulator waveguides with highly
efficient organic electro-optic (EO) cladding materials to enable small drive
voltages and sub-millimeter device lengths. In our experiments, we use an SOH
IQ modulator with a {\pi}-voltage of 1.6 V to generate 100 GBd 16QAM signals.
This is the first time that the 100 GBd mark is reached with an IQ modulator
realized on a semiconductor substrate, leading to a single-polarization line
rate of 400 Gbit/s. The peak-to-peak drive voltages amount to 1.5 Vpp,
corresponding to an electrical energy dissipation in the modulator of only 25
fJ/bit
Electrically packaged silicon-organic hybrid (SOH) I/Q-modulator for 64 GBd operation
Silicon-organic hybrid (SOH) electro-optic (EO) modulators combine small
footprint with low operating voltage and hence low power dissipation, thus
lending themselves to on-chip integration of large-scale device arrays. Here we
demonstrate an electrical packaging concept that enables high-density
radio-frequency (RF) interfaces between on-chip SOH devices and external
circuits. The concept combines high-resolution
printed-circuit boards with technically simple metal wire bonds and is amenable
to packaging of device arrays with small on-chip bond pad pitches. In a set of
experiments, we characterize the performance of the underlying RF building
blocks and we demonstrate the viability of the overall concept by generation of
high-speed optical communication signals. Achieving line rates (symbols rates)
of 128 Gbit/s (64 GBd) using quadrature-phase-shiftkeying (QPSK) modulation and
of 160 Gbit/s (40 GBd) using 16-state quadrature-amplitudemodulation (16QAM),
we believe that our demonstration represents an important step in bringing SOH
modulators from proof-of-concept experiments to deployment in commercial
environments
A verified equivalent-circuit model for slotwaveguide modulators
We formulate and experimentally validate an equivalent-circuit model based on
distributed elements to describe the electric and electro-optic (EO) properties
of travellingwave silicon-organic hybrid (SOH) slot-waveguide modulators. The
model allows to reliably predict the small-signal EO frequency response of the
modulators exploiting purely electrical measurements of the frequency-dependent
RF transmission characteristics. We experimentally verify the validity of our
model, and we formulate design guidelines for an optimum trade-off between
optical loss due to free-carrier absorption (FCA), electro-optic bandwidth, and
{\pi}-voltage of SOH slot-waveguide modulators
Non-sliced Optical Arbitrary Waveform Measurement (OAWM) Using a Silicon Photonic Receiver Chip
Comb-based optical arbitrary waveform measurement (OAWM) techniques can
overcome the bandwidth limitations of conventional coherent detection schemes
and may have disruptive impact on a wide range of scientific and industrial
applications. Over the previous years, different OAWM schemes have been
demonstrated, showing the performance and the application potential of the
concept in laboratory experiments. However, these demonstrations still relied
on discrete fiber-optic components or on combinations of discrete coherent
receivers with integrated optical slicing filters that require complex tuning
procedures to achieve the desired performance. In this paper, we demonstrate
the first wavelength-agnostic OAWM front-end that is integrated on a compact
silicon photonic chip and that neither requires slicing filters nor active
controls. Our OAWM system comprises four IQ receivers, which are accurately
calibrated using a femtosecond mode-locked laser and which offer a total
acquisition bandwidth of 170 GHz. Using sinusoidal test signals, we measure a
signal-to-noise-and-distortion ratio (SINAD) of 30 dB for the reconstructed
signal, which corresponds to an effective number of bits (ENOB) of 4.7 bit,
where the underlying electronic analog-to-digital converters (ADC) turn out to
be the main limitation. The performance of the OAWM system is further
demonstrated by receiving 64QAM data signals at symbol rates of up to 100 GBd,
achieving constellation signal-to-noise ratios (CSNR) that are on par with
those obtained for conventional coherent receivers. In a theoretical
scalability analysis, we show that increasing the channel count of non-sliced
OAWM systems can improve both the acquisition bandwidth and the signal quality.
We believe that our work represents a key step towards out-of-lab use of highly
compact OAWM systems that rely on chip-scale integrated optical front-ends
Comb-based WDM transmission at 10 Tbit/s using a DC-driven quantum-dash mode-locked laser diode
Chip-scale frequency comb generators have the potential to become key
building blocks of compact wavelength-division multiplexing (WDM) transceivers
in future metropolitan or campus-area networks. Among the various comb
generator concepts, quantum-dash (QD) mode-locked laser diodes (MLLD) stand out
as a particularly promising option, combining small footprint with simple
operation by a DC current and offering flat broadband comb spectra. However,
the data transmission performance achieved with QD-MLLD was so far limited by
strong phase noise of the individual comb tones, restricting experiments to
rather simple modulation formats such as quadrature phase shift keying (QPSK)
or requiring hard-ware-based compensation schemes. Here we demonstrate that
these limitations can be over-come by digital symbol-wise phase tracking
algorithms, avoiding any hardware-based phase-noise compensation. We
demonstrate 16QAM dual-polarization WDM transmission on 38 channels at an
aggregate net data rate of 10.68 Tbit/s over 75 km of standard single-mode
fiber. To the best of our knowledge, this corresponds to the highest data rate
achieved through a DC-driven chip-scale comb generator without any
hardware-based phase-noise reduction schemes
- …