270 research outputs found
If Not Here, There. Explaining Machine Learning Models for Fault Localization in Optical Networks
Machine Learning (ML) is being widely investigated to automate safety-critical tasks in optical-network management. However, in some cases, decisions taken by ML models are hard to interpret, motivate and trust, and this lack of explainability complicates ML adoption in network management. The rising field of Explainable Artificial Intelligence (XAI) tries to uncover the reasoning behind the decision-making of complex ML models, offering end-users a stronger sense of trust towards ML-Automated decisions. In this paper we showcase an application of XAI, focusing on fault localization, and analyze the reasoning of the ML model, trained on real Optical Signal-To-Noise Ratio measurements, in two scenarios. In the first scenario we use measurements from a single monitor at the receiver, while in the second we also use measurements from multiple monitors along the path. With XAI, we show that additional monitors allow network operators to better understand model's behavior, making ML model more trustable and, hence, more practically adoptable
Cu-NMR study on the disordered quantum spin magnet with the Bose-glass ground state
Cu-NMR study has been performed on the disordered spin-gap system
Tl1-xKxCuCl3 In the high-field H > HC=\Delta/\mu_B, where \Delta is the
spin-gap, the hyperfine field becomes extremely inhomogeneous at low
temperatures due to the field-induced magnetic order, indicating that the
ordered spin state must be different from the pure TlCuCl3. In the low field H
< HC, a saturating behavior in the longitudinal nuclear spin relaxation rate
1/T1 was observed at low temperatures, indicating existence of the magnetic
ground state proposed to be Bose-glass phase by Fisher.Comment: RHMF200
Single parity check multi-core modulation for power efficient spatial super-channels
We investigate multi-core modulation formats for spatial super-channels using a single parity check on PDM-QPSK symbols. Compared to per-core PDM-QPSK, we show improvements in required OSNR of up to 1.8 dB, with minimal impact on spectral efficiency
Anomalous vortex dynamics in spin-triplet superconductor UTe
The vortex dynamics in the spin-triplet superconductor, UTe, are studied
by measuring the DC electrical resistivity with currents along the -axis
under magnetic fields along the -axis. Surprisingly, we have discovered an
island region of low critical current deep inside the superconducting (SC)
state, well below the SC upper critical field, attributed to a weakening of
vortex pinning. Notably, this region coincides with the recently proposed
intermediate-field SC state. We discuss the possibility of nonsingular vortices
in the intermediate state, where SC order parameter does not vanish entirely in
the vortex cores due to the mixing of multiple SC components
Clock and Data Recovery-Free Data Communications Enabled by Multi-core Fiber with Low Thermal Sensitivity of Skew
Optical switching has the potential to scale the
capacity of data center networks (DCN) with a simultaneously
reduction in latency and power consumption. One of the main
challenges of optically-switched DCNs is the need for fast clock
and data recovery (CDR). Because the DCN traffic is dominated
by small packets, the CDR locking time is required to be less
than one nanosecond for achieving high network throughput.
This need for sub-nanosecond CDR locking time has motivated
research on optical clock synchronization techniques, which
deliver synchronized clock signals through optical fibers such that
the CDR modules in each transceiver only need to track the slow
change of clock phase, due to change of the time of flight as temperature varies. It is desired to remove the need for clock phase
tracking (and thereby the CDR modules) if the temperatureinduced clock phase drift can be significantly reduced, which
would reduce the power consumption and the cost of transceivers.
Previous studies have shown that the temperature-induced skew
change between multi-core fiber (MCF) cores can be forty
times lower than that of standard single mode fibers. Thus,
clock-synchronized transmission maybe possible by using two
different MCF cores for clock and data transmission, respectively,
enabling the sharing of an optical clock with stable clock phase.
To investigate the potential of MCF for CDR-free short-reach
communications, we first improve the measurement method of
the temperature dependent inter-core skew change by using a
modified delay interferometer, achieving a resolution of 3.8 femtoseconds for accurate inter-core skew measurements. Building
on the MCF measurement results, we carried out an MCF-based
clock-synchronized transmission experiment, demonstrating the
feasibility of CDR-free data communications over a temperature
range of 43 ◦C that meets DCN requirements
Dynamic skew measurements in 7, 19 and 22-core multi core fibers
We report simultaneous dynamic inter-core skew measurements between 7 cores of several homogeneous MCFs. The largest variation was 4.33 picoseconds for 31km span with diminishing influence of mechanical vibrations, temperature, core-layout and wavelength observed
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