33 research outputs found
Chip-scale optical frequency comb sources for terabit communications
To keep up with the ever-increasing data transmission speed needs, data center interconnects are scaling up to provide multi-Tbit/s connectivity. These links require a high number of WDM channels, while the associated transceivers should be compact and energy efficient. Scaling 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 for Tbit/s WDM links
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
Chip-scale optical frequency comb sources for terabit communications
To keep up with the ever-increasing data transmission speed needs, data center interconnects are scaling up to provide multi-Tbit/s connectivity. These links require a high number of WDM channels, while the associated transceivers should be compact and energy efficient. Scaling 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 for Tbit/s WDM links
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
Ultra-broadband polarization beam splitter and rotator based on 3D-printed waveguides
Multi-photon lithography has emerged as a powerful tool for photonic
integration, allowing to complement planar photonic circuits by 3D-printed
freeform structures such as waveguides or micro-optical elements. These
structures can be fabricated with high precision on the facets of optical
devices and lend themselves to highly efficient package-level
chip-chip-connections in photonic assemblies. However, plain light transport
and efficient coupling is far from exploiting the full geometrical design
freedom that is offered by 3D laser lithography. Here, we extend the
functionality of 3D-printed optical structures to manipulation of optical
polarization states. We demonstrate compact ultra-broadband polarization beam
splitters (PBS) that can be combined with polarization rotators (PR) and
mode-field adapters into a monolithic 3D-printed structure, fabricated directly
on the facets of optical devices. In a proof-of-concept experiment, we
demonstrate measured polarization extinction ratios beyond 11 dB over a
bandwidth of 350 nm at near-infrared (NIR) telecommunication wavelengths around
1550 nm. We demonstrate the viability of the device by receiving a 640 Gbit/s
dual-polarization data signal using 16-state quadrature amplitude modulation
(16QAM), without any measurable optical-signal-to-noise-ratio (OSNR) penalty
compared to a commercial PBS.Comment: 11 pages and 4 figures in the main part + 7 pages and 4 figures in
the supplementar
Mode-locked laser timing jitter limitation in optically enabled, spectrally sliced ADCs
Novel analog-to-digital converter (ADC) architectures are motivated by the
demand for rising sampling rates and effective number of bits (ENOB). The main
limitation on ENOB in purely electrical ADCs lies in the relatively high jitter
of oscillators, in the order of a few tens of fs for state-of-the-art
components. When compared to the extremely low jitter obtained with
best-in-class Ti:sapphire mode-locked lasers (MLL), in the attosecond range, it
is apparent that a mixed electrical-optical architecture could significantly
improve the converters' ENOB. We model and analyze the ENOB limitations arising
from optical sources in optically enabled, spectrally sliced ADCs, after
discussing the system architecture and implementation details. The phase noise
of the optical carrier, serving for electro-optic signal transduction, is shown
not to propagate to the reconstructed digitized signal and therefore not to
represent a fundamental limit. The optical phase noise of the MLL used to
generate reference tones for individual slices also does not fundamentally
impact the converted signal, so long as it remains correlated among all the
comb lines. On the other hand, the timing jitter of the MLL, as also reflected
in its RF linewidth, is fundamentally limiting the ADC performance, since it is
directly mapped as jitter to the converted signal. The hybrid nature of a
photonically enabled, spectrally sliced ADC implies the utilization of a number
of reduced bandwidth electrical ADCs to convert parallel slices, resulting in
the propagation of jitter from the electrical oscillator supplying their clock.
Due to the reduced sampling rate of the electrical ADCs, as compared to the
overall system, the overall noise performance of the presented architecture is
substantially improved with respect to a fully electrical ADC
Ultrafast optical ranging using microresonator soliton frequency combs
Light detection and ranging (LIDAR) is critical to many fields in science and
industry. Over the last decade, optical frequency combs were shown to offer
unique advantages in optical ranging, in particular when it comes to fast
distance acquisition with high accuracy. However, current comb-based concepts
are not suited for emerging high-volume applications such as drone navigation
or autonomous driving. These applications critically rely on LIDAR systems that
are not only accurate and fast, but also compact, robust, and amenable to
cost-efficient mass-production. Here we show that integrated dissipative
Kerr-soliton (DKS) comb sources provide a route to chip-scale LIDAR systems
that combine sub-wavelength accuracy and unprecedented acquisition speed with
the opportunity to exploit advanced photonic integration concepts for
wafer-scale mass production. In our experiments, we use a pair of free-running
DKS combs, each providing more than 100 carriers for massively parallel
synthetic-wavelength interferometry. We demonstrate dual-comb distance
measurements with record-low Allan deviations down to 12 nm at averaging times
of 14 s as well as ultrafast ranging at unprecedented measurement rates of
up to 100 MHz. We prove the viability of our technique by sampling the
naturally scattering surface of air-gun projectiles flying at 150 m/s (Mach
0.47). Combining integrated dual-comb LIDAR engines with chip-scale
nanophotonic phased arrays, the approach could allow widespread use of compact
ultrafast ranging systems in emerging mass applications.Comment: 9 pages, 3 figures, Supplementary information is attached in
'Ancillary files