401 research outputs found
Silicon optical modulators
Optical technology is poised to revolutionise short reach interconnects. The leading candidate technology is silicon photonics, and the workhorse of such interconnect is the optical modulator. Modulators have been improved dramatically in recent years. Most notably the bandwidth has increased from the MHz to the multi GHz regime in little more than half a decade. However, the demands of optical interconnect are significant, and many questions remain unanswered as to whether silicon can meet the required performance metrics. Minimising metrics such as the energy per bit, and device footprint, whilst maximising bandwidth and modulation depth are non trivial demands. All of this must be achieved with acceptable thermal tolerance and optical spectral width, using CMOS compatible fabrication processes. Here we discuss the techniques that have, and will, be used to implement silicon optical modulators, as well as the outlook for these devices, and the candidate solutions of the future
Modeling of Silicon Photonic Devices for Optical Interconnect Transceiver Circuit Design
Optical interconnect system efficiency is dependent on the ability to optimize the transceiver circuitry for low-power and high-bandwidth operation, motivating co-simulation environments with compact optical device simulation models. This chapter presents compact Verilog-A silicon carrier-injection and carrier-depletion ring modulator models which accurately capture both nonlinear electrical and optical dynamics. Experimental verification of the carrier-injection ring modulator model is performed both at 8 Gb/s with symmetric drive signals to study the impact of pre-emphasis pulse duration, pulse depth, and dc bias, and at 9 Gb/s with a 65-nm CMOS driver capable of asymmetric pre-emphasis pulse duration. Experimental verification of the carrier-depletion ring modulator model is performed at 25 Gb/s with a 65-nm CMOS driver capable of asymmetric equalization
Single chip photonic deep neural network with accelerated training
As deep neural networks (DNNs) revolutionize machine learning, energy
consumption and throughput are emerging as fundamental limitations of CMOS
electronics. This has motivated a search for new hardware architectures
optimized for artificial intelligence, such as electronic systolic arrays,
memristor crossbar arrays, and optical accelerators. Optical systems can
perform linear matrix operations at exceptionally high rate and efficiency,
motivating recent demonstrations of low latency linear algebra and optical
energy consumption below a photon per multiply-accumulate operation. However,
demonstrating systems that co-integrate both linear and nonlinear processing
units in a single chip remains a central challenge. Here we introduce such a
system in a scalable photonic integrated circuit (PIC), enabled by several key
advances: (i) high-bandwidth and low-power programmable nonlinear optical
function units (NOFUs); (ii) coherent matrix multiplication units (CMXUs); and
(iii) in situ training with optical acceleration. We experimentally demonstrate
this fully-integrated coherent optical neural network (FICONN) architecture for
a 3-layer DNN comprising 12 NOFUs and three CMXUs operating in the telecom
C-band. Using in situ training on a vowel classification task, the FICONN
achieves 92.7% accuracy on a test set, which is identical to the accuracy
obtained on a digital computer with the same number of weights. This work lends
experimental evidence to theoretical proposals for in situ training, unlocking
orders of magnitude improvements in the throughput of training data. Moreover,
the FICONN opens the path to inference at nanosecond latency and femtojoule per
operation energy efficiency.Comment: 21 pages, 10 figures. Comments welcom
Silicon photonic modulators for PAM transmissions
High-speed optical interconnects are crucial for both data centers and high performance computing systems. High power consumption and limited device bandwidth have hindered the move to higher optical transmission speeds. Integrated optical transceivers in silicon photonics (SiP) using pulse-amplitude modulation (PAM) are a promising solution to increase data rates. In this paper, we review recent progress in SiP for PAM transmissions. We focus on materials and technologies available CMOS-compatible photonics processes. Performance metrics of SiP modulators and crucial considerations for high-speed PAM transmissions are discussed. Various driving strategies to achieve optical PAM signals are presented. Some of the state-of-the-art SiP PAM modulators and integrated transmitters are reviewed
Cascaded uncoupled dual-ring modulator
We demonstrate that by coherent driving two uncoupled rings in same
direction, the effective photon circulating time in the dual ring modulator is
reduced, with increased modulation quality. The inter-ring detuning dependent
photon dynamics, Q-factor, extinction ratio and optical modulation amplitude of
two cascaded silicon ring resonators are studied and compared with that of a
single ring modulator. Experimentally measured eye diagrams, together with
coupled mode theory simulations, demonstrate the enhancement of dual ring
configuration at 20 Gbps with a Q ~ 20,000
Integrated flexible-grid WDM transmitter using an optical frequency comb in microring modulators
Advanced optical interconnects require high-speed links,
which can be achieved by combining high channel rates
with wavelength-division multiplexing (WDM). We
report a multi-channel transmitter using cascaded
microring modulators (MRMs) in silicon photonics. One
MRM works as a flexible-grid optical comb generator,
while the others work as channel modulators. With a
single-wavelength laser input, we achieve flexible
channel spacing (up to 25 GHz) with a tone-to-noise ratio
(TNR) above 54 dB, all at low power consumption (less
than 4.6 mW). We examine experimentally multichannel
transmission modulating data onto adjacent
comb lines without significant signal crosstalk. This
single-laser, flexible-grid WDM transmitter is a
scalable solution: more comb lines can be obtained
using uncoupled MRMs in series. This is the first
demonstration of monolithic integration of a comb
generator and multi-channel modulators for ultracompact,
power-efficient WDM photonic
interconnects
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