1,158 research outputs found
High-speed PAM4-based Optical SDM Interconnects with Directly Modulated Long-wavelength VCSEL
This paper reports the demonstration of high-speed PAM-4 transmission using a
1.5-{\mu}m single-mode vertical cavity surface emitting laser (SM-VCSEL) over
multicore fiber with 7 cores over different distances. We have successfully
generated up to 70 Gbaud 4-level pulse amplitude modulation (PAM-4) signals
with a VCSEL in optical back-to-back, and transmitted 50 Gbaud PAM-4 signals
over both 1-km dispersion-uncompensated and 10-km dispersion-compensated in
each core, enabling a total data throughput of 700 Gbps over the 7-core fiber.
Moreover, 56 Gbaud PAM-4 over 1-km has also been shown, whereby unfortunately
not all cores provide the required 3.8 10 bit error rate (BER)
for the 7% overhead-hard decision forward error correction (7% OH HDFEC). The
limited bandwidth of the VCSEL and the adverse chromatic dispersion of the
fiber are suppressed with pre-equalization based on accurate end-to-end channel
characterizations. With a digital post-equalization, BER performance below the
7% OH-HDFEC limit is achieved over all cores. The demonstrated results show a
great potential to realize high-capacity and compact short-reach optical
interconnects for data centers.Comment: 7 pages, accepted to publication in 'Journal of Lightwave Technology
(JLT
White Gaussian Noise Based Capacity Estimate and Characterization of Fiber-Optic Links
We use white Gaussian noise as a test signal for single-mode and multimode
transmission links and estimate the link capacity based on a calculation of
mutual information. We also extract the complex amplitude channel estimations
and mode-dependent loss with high accuracy.Comment: submitted to The Optical Networking and Communication Conference
(OFC) 201
A survey on fiber nonlinearity compensation for 400 Gbps and beyond optical communication systems
Optical communication systems represent the backbone of modern communication
networks. Since their deployment, different fiber technologies have been used
to deal with optical fiber impairments such as dispersion-shifted fibers and
dispersion-compensation fibers. In recent years, thanks to the introduction of
coherent detection based systems, fiber impairments can be mitigated using
digital signal processing (DSP) algorithms. Coherent systems are used in the
current 100 Gbps wavelength-division multiplexing (WDM) standard technology.
They allow the increase of spectral efficiency by using multi-level modulation
formats, and are combined with DSP techniques to combat the linear fiber
distortions. In addition to linear impairments, the next generation 400 Gbps/1
Tbps WDM systems are also more affected by the fiber nonlinearity due to the
Kerr effect. At high input power, the fiber nonlinear effects become more
important and their compensation is required to improve the transmission
performance. Several approaches have been proposed to deal with the fiber
nonlinearity. In this paper, after a brief description of the Kerr-induced
nonlinear effects, a survey on the fiber nonlinearity compensation (NLC)
techniques is provided. We focus on the well-known NLC techniques and discuss
their performance, as well as their implementation and complexity. An extension
of the inter-subcarrier nonlinear interference canceler approach is also
proposed. A performance evaluation of the well-known NLC techniques and the
proposed approach is provided in the context of Nyquist and super-Nyquist
superchannel systems.Comment: Accepted in the IEEE Communications Surveys and Tutorial
A 3 Gb/s optical detector in standard CMOS for 850 nm optical communication
This paper presents a monolithic optical detector, consisting of an integrated photodiode and a preamplifier in a standard 0.18-/spl mu/m CMOS technology. A data rate of 3 Gb/s at BER <10/sup -11/ was achieved for /spl lambda/=850 nm with 25-/spl mu/W peak-peak optical power. This data rate is more than four times than that of current state-of-the-art optical detectors in standard CMOS reported so far. High-speed operation is achieved without reducing circuit responsivity by using an inherently robust analog equalizer that compensates (in gain and phase) for the photodiode roll-off over more than three decades. The presented solution is applicable to various photodiode structures, wavelengths, and CMOS generations
Near minimum bit-error rate equalizer adaptation for PRML systems
Receivers for partial response maximum-likelihood systems typically use a linear equalizer followed by a Viterbi detector. The equalizer tries to confine the channel intersymbol interference to a short span in order to limit the implementation complexity of the Viterbi detector. Equalization is usually made adaptive in order to compensate for channel variations. Conventional adaptation techniques, e.g. LMS, are in general suboptimal in terms of bit-error rate. In this paper we present a new equalizer adaptation algorithm that seeks to minimize bit-error rate at the Viterbi detector output. The algorithm extracts information from the sequenced amplitude margin (SAM) histogram and incorporates a selection mechanism that focuses adaptation on particular data and noise realizations. From a complexity standpoint, the algorithm is as simple as the conventional LMS algorithm. Simulation results, for an idealized optical storage channel, confirm a substantial performance improvement relative to existing adaptation algorithm
Available Techniques for Magnetic Hard Disk Drive Read Channel Equalization
This paper presents an extensive, non-exhaustive, study of available hard disk drive read channel equalization techniques used in the storage and readback of magnetically stored information. The physical elements and basic principles of the storage processes are introduced together with the basic theoretical definitions and models. Both read and write processes in magnetic storage are explained along with the definition of simple key concepts such as user bit density, intersymbol interference, linear and areal density, read head pulse response models, and coding algorithm
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