Coherent Network Research Articles

Mutually Protected Coherent P2MP Networks Enabled by Frequency Comb and Injection Locking

We propose a novel network protection scheme that features mutual protection between adjacent P2MP coherent networks without requiring complex switching or redundant devices. High system availability and fast service restoration have been achieved by utilizing coherent transceivers with remotely delivered optical carriers that are injection locked to an optical frequency comb. System functionality and performance have been verified experimentally. The mutual protection design was also verified using commercially available coherent optics. Full-duplex design that features simultaneous bidirectional transmission using the same wavelength has also been tested in the coherent P2MP system.

HIBISCUS: Simulator for the development of control strategies for coherent beam combining lasers with PISTIL technique

CBC (Coherent Beam Combining) is a key technology for the realisation of intense lasers. In this context, PISTIL (PISton and TILt interferometry), a precise metrology tool for measuring segmented wave surfaces, has been developed and used in particular to characterise and diagnose CBC ultrafast and digital laser in the framework of the XCAN (X Coherent Amplification Network) project at the École Polytechnique. We propose here to use it in a way to help the optimisation of control techniques by including PISTIL in an XCAN type CBC laser simulator. This will allow an easy tuning of the control laws, outside the clean rooms in which these large lasers are deployed and without the need to start them up.

Identification of cycle lane priorities based on observed and potential cyclist trips using GIS, the case of the Metropolitan Area of Mendoza, Argentina

ABSTRACT In Latin America and developing countries, urban planners often lack sufficient data on cyclists’ modal share and profile to establish effective cycling lane networks. Mendoza, Argentina, is such a city. This research aimed to identify adequate locations for new cycle lanes by speculating on potential cycle trips from observed patterns of existing cyclists for a coherent demand-based network. The study proposed a novel, simple, cost-effective Geographic Information Systems model that uses spatial and human data and presents results cartographically for policymakers. Statistical analysis of observed bicycle trips enabled constructing a local profile of cyclists, from which ‘potential trips’ were speculated: trips made by other modes, but which could have been biked given their distance, duration, purpose, and the traveler’s age. Geo-referencing observed and potential trips to their ‘sub-zones’ of origin and destination produced a migratory synthesis map highlighting general flows and densities. Superimposing this on the current cycling infrastructure exposed the critical gaps. As a broader aim, this geomatic method is readily transferable to other developing world settings. Actions for Mendoza and broader applications are proposed, significant limitations discussed, and further research suggested, noting issues of gender equity and safety.

Experimental demonstration of coherent photonic neural computing based on a Fabry–Perot laser with a saturable absorber

As Moore’s law has reached its limits, it is becoming increasingly difficult for traditional computing architectures to meet the demands of continued growth in computing power. Photonic neural computing has become a promising approach to overcome the von Neuman bottleneck. However, while photonic neural networks are good at linear computing, it is difficult to achieve nonlinear computing. Here, we propose and experimentally demonstrate a coherent photonic spiking neural network consisting of Mach–Zehnder modulators (MZMs) as the synapse and an integrated quantum-well Fabry–Perot laser with a saturable absorber (FP-SA) as the photonic spiking neuron. Both linear computation and nonlinear computation are realized in the experiment. In such a coherent architecture, two presynaptic signals are modulated and weighted with two intensity modulation MZMs through the same optical carrier. The nonlinear neuron-like dynamics including temporal integration, threshold, and refractory period are successfully demonstrated. Besides, the effects of frequency detuning on the nonlinear neuron-like dynamics are also explored, and the frequency detuning condition is revealed. The proposed hardware architecture plays a foundational role in constructing a large-scale coherent photonic spiking neural network.

400Gb/s real-time coherent PON based on a silicon photonic integrated transceiver.

We experimentally demonstrate the real-time 100/200/400 Gb/s/λ coherent passive optical networks (PONs) based on silicon photonic integrated transceiver. We investigate different configuration schemes of coherent PONs including: (1) using a Erbium doped optical fiber amplifier (EDFA) as a booster at the transmitter side; (2) using a semiconductor optical amplifier (SOA) as a booster at the transmitter side; (3) using EDFA at the transmitter side and a pre-amplified SOA at receiver side; (4) using an SOA at the transmitter side and an SOA at the receiver side. The performance of these schemes for different data rates of downstream transmission is evaluated, and the appropriate choices under different circumstances are analyzed. The real-time experimental results indicate that the EDFA can be replaced by SOA as a booster at the transmitter side in 100/200 Gb/s/λ coherent PON based on the dual-polarization QPSK (DP-QPSK) scheme with a small performance penalty. In dual-polarization a 16 quadrature amplitude modulation (DP-16QAM) 400 G/s/λ PON system, EDFA booster is preferred because an SOA introduces more nonlinearity for the 16QAM scheme. The power budget of 32.5 dB is achieved for 400 Gb/s/λ coherent PON after the 20 km standard single mode fiber (SSMF) transmission under the soft-decision feedforward error correction (SD-FEC) threshold.

Flexible and adaptive coherent PON for next-generation optical access network [Invited

With the official adoption of the single-wavelength 50G PON standard at the International Telecommunication Union Study Group 15 (ITU-T SG15) meeting, both industry and academia have started extensive research on the next-generation optical access network beyond 50G. It is envisioned that 100G and 200G per wavelength and even beyond will be required in the next-generation optical access network to support the continuously growing bandwidth demands. Coherent passive optical network (C-PON), which is based on multi-access coherent optics and digital signal processing (DSP), appears to be a promising candidate for future 100/200G and even beyond single-wavelength PON, thanks to its superior sensitivity compared with current direct-detection based PONs. Actually, multi-access coherent optics brings many benefits to the optical access network beyond the improvement of sensitivity. In this invited paper, we review recent studies and progress on the flexible C-PON for optical access network in terms of access speed, multiple-access architecture, and deployment scenarios. Rate-adaptive coherent access is first introduced in this paper as a promising solution to achieve flexible C-PON. Adaptive modulation formats based on constellation shaping is highlighted to realize fine granularity of information rate and wide flexibility. We have also discussed the flexible multiplexing schemes beyond TDM, to take the full advantages of coherent access. Finally, we analyze the flexible deployment scenarios under the large power budgets thanks to coherent detection. All these flexibilities provided by coherent access would be interesting and beneficial in the next generation optical access network.

The overlap between burnout and depression through a different lens: A multi-method study

• The latent correlation between burnout and depression was positive and strong after controlling for a general factor and acquiescence • Burnout and depression symptoms formed a single syndrome in network analysis, with fatigue indicators acting as bridge symptoms. • Findings from latent profile analysis revealed classes ordered by symptom severity. • Individuals exhibiting more burnout and depression were also more likely to suffer from work distress. Depression and burnout are highly overlapping constructs, according to many correlational, factor, network, and mixture analysis studies. However, the latent correlation between the unique factors of burnout and depression might be confounded by a general factor of distress, and acquiescence (i.e., the tendency to agree more than disagree when responding to self-report items). In the current study, we performed an in-depth investigation on the latent structure of burnout and depression controlling for a general factor and acquiescence, and using a combination of random-intercept bifactor, network, and latent profile analysis. Participants were 584 nurse professionals (79% nurse technicians and assistants, 21% nurses), with ages ranging from 20 to 65 years ( M = 35.41; SD = 9.54), who responded to measures of depression symptoms, burnout, and work stress. Results revealed a latent overlap between depression and burnout, even once acquiescence ( r = .74), and a general factor was accounted for ( r = .57). Burnout and depression indicators formed a coherent network of associated symptoms, with fatigue and lack of energy acting as bridge symptoms. The latent profile analysis yielded five classes that once again suggested a high dependence between burnout and depression. We conclude that controlling for acquiescence and a general factor does not eliminate the high overlap between burnout and depression, that fatigue symptoms bear clinical importance as a trigger to more severe mental suffering in occupational settings, and that burnout involves a continuum of work stress.

Resolving Galactic binaries using a network of space-borne gravitational wave detectors

Extracting gravitational wave (GW) signals from individual Galactic binaries (GBs) against their self-generated confusion noise is a key data analysis challenge for space-borne detectors operating in the $\ensuremath{\approx}0.1$ to $\ensuremath{\approx}10\text{ }\text{ }\mathrm{mHz}$ range. Given the likely prospect that there will be multiple such detectors, namely Laser Interferometer Space Antenna (LISA), Taiji, and Tianqin, with overlapping operational periods in the next decade, it is important to examine the extent to which the joint analysis of their data can benefit GB resolution and parameter estimation. To investigate this, we use realistic simulated LISA and Taiji data containing the set of $30\ifmmode\times\else\texttimes\fi{}{10}^{6}$ GBs used in the first LISA data challenge (Radler) and an iterative source extraction method called GBSIEVER introduced in an earlier work. We find that a coherent network analysis of LISA-Taiji data boosts the number of confirmed sources by $\ensuremath{\approx}75%$ over that from a single detector. The residual after subtracting out the reported sources from the data of any one of the detectors is much closer to the confusion noise expected from an ideal, but infeasible, multisource resolution method that perfectly removes all sources above a given signal-to-noise ratio threshold. While parameter estimation for sources common to both the single detector and network improves broadly in line with the enhanced signal-to-noise ratio of GW sources in the latter, deviation from the scaling of error variance predicted by Fisher information analysis is observed for a subset of the parameters.

A Distributed Lyapunov-Based Redesign Approach for Heterogeneous Uncertain Agents With Cooperation-Competition Interactions.

A swarming behavior problem is investigated in this article for heterogeneous uncertain agents with cooperation-competition interactions. In such a problem, the agents are described by second-order continuous systems with different intrinsic nonlinear terms, which satisfies the "linearity-in-parameters" condition, and the agents' models are coupled together through a distributed protocol containing the information of competitive neighbors. Then, for four different types of cooperation-competition networks, a distributed Lyapunov-based redesign approach is proposed for the heterogeneous uncertain agents, where the distributed controller and the estimation laws of unknown parameters are obtained. Under their joint actions, the heterogeneous uncertain multiagent system can achieve distributed stabilization for structurally unbalanced networks and output bipartite consensus for structurally balanced networks. In particular, the concept of coherent networks is proposed for structurally unbalanced directed networks, which is beneficial to the design of distributed controllers. Finally, four illustrative examples are given to show the effectiveness of the designed distributed controller.

Chemical Composition of Tagetes patula Flowers Essential Oil and Hepato-Therapeutic Effect against Carbon Tetrachloride-Induced Toxicity (In-Vivo)

The liver is a crucial organ among body organs due to its wide functions, in particular, detoxification and metabolism. Exposure to detrimental chemicals or viral infections may provoke liver dysfunction and ultimately induce liver tissue damage. Finding natural substances for liver disease treatment to overcome the conventional treatments' side effects has attracted the attention of researchers worldwide. Our current work was conducted to investigate the hepato-therapeutic activities of essential oil (EO) isolated from Tagetes patula flowers. EO was extracted using the hydro-distillation (HD) technique and its chemical composition was identified by GC/MS. Then, the hepatic treatment potential of extracted EO was evaluated in vivo against CCL4 in rats. HD of T. patula flowers yielded highly chemical constituents of EO along with significant antioxidant potential. A coherent molecular network was fashioned via the Global Natural Products Social Molecular Networking (GNPS) to visualize the essential components and revealed that the sesquiterpene (E)-β-caryophyllene was the most predominant volatile constituent which accounted for 24.1%. The treatment of CCL4 led to significant induced oxidative stress markers malonaldehyde, total protein, and non-protein sulfhydryl, as well as elevated serum aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, and bilirubin. In addition, it disrupted the level of lipid profile. The post-treatment using T. patula EO succeeded in relieving all toxic effects of CCl4 and recuperating the histopathological signs induced by CCL4. Silymarin was used as a standard hepatoprotective agent. The obtained results demonstrated that the extracted EO exerted high protective activities against the toxicity of CCL4. Moreover, the T. patula flowers EO can be used as a natural remedy to relieve many contemporary liver diseases related to oxidative stress.

Near-Field Compensation for Coherent Radar Networks

With radar networks, the resolution of critical radar parameters such as Doppler and angle can be improved compared to a single radar sensor. As the network’s aperture is considerably larger than that of a single radar, a much higher angular resolution is achieved. However, with a large aperture, range-dependent phase deviations, that is, near-field effects, occur and affect the angle estimation. In this work, these near-field effects are evaluated exemplarily for a coherent network. Furthermore, a new strategy to compensate for those network near-field effects is proposed and demonstrated based on measurements. The benefits of the near-field compensation are emphasized by comparing the network’s angle-estimation capabilities with and without compensated near-field effects.

Methods for measuring the spatial mobility of tourists using a network theory approach

The present study uses the methodological tools of network theory to investigate the spatial movements of tourists in the sample area, which is the South Transdanubian tourism region of Hungary. The basic idea of the study is that tourist movements across settlements in a larger tourist destination make a coherent network. As long as the approach is correct, this network can be measured by properties that are characteristic of networks, such as centrality or degree. A review of the methodology of similar studies previously published on the subject has been used to supplement the method of analysis used below. As a result, the study not only characterised the sample area municipalities in terms of network characteristics, but also classified them into clusters for strategic planning purposes on the basis of the mobility propensity of the tourists staying there.

Potential Climate Impacts of Hydrological Alterations and Discharge Variabilities of the Mura, Drava, and Danube Rivers on the Natural Resources of the MDD UNESCO Biosphere Reserve

This study investigated hydrological alterations in the sections of the Mura, Drava, and Danube rivers, which together form a unique river landscape proclaimed by UNESCO as the Transboundary Biosphere Reserve Mura, Drava, and Danube (TBR MDD). A coherent network of 12 major protected areas along the rivers highlights their ecological value, which could be endangered by climate change and consequent environmental changes. Statistical analyses, such as the homogeneity test, Mann–Kendall trend test of monthly and seasonal discharges, and empirical probabilities of daily discharges, were applied to discharge data series (1960–2019) from six hydrological stations prior to the calculation of indicators of hydrologic alteration (IHA). This method could be a helpful tool for recognizing the changes in hydrological regimes that can affect river ecosystems. The 33 indicators were organized into five groups. The results showed a decrease in low pulse duration and increase in rise/fall rates and the number of reversals. From an ecological perspective, the results obtained for the probabilities of long flooding periods were particularly significant. They drastically decreased for all three rivers on their stretches within the reserve. According to IHA modeling results, the river sections analyzed were moderately altered with global indicator values between 0.5 and 0.75. The most pronounced hydrological alterations were associated with the frequency and duration of low and high pulses and the rate and frequency of changes in water condition, which could have a significant impact on the ecological values of the TBR MDD. In addition, results show more pronounced climate impact versus human activities.

Pocket parks in Łódź as an element of improving urban resilence in the city centre

Urban resilience is one of the main challenges for the European cities, especially in densely built-up central areas. Crucial problems occurring in urbanized areas include air pollution, environmental degradation, insufficient number of recreational areas, flooding, and heavy heat. Greenery is one of the factors that can contribute to the improvement of the urban resilience. City centres are especially exposed to the problem of inadequate number of natural areas. In order to improve living conditions in cities, green infrastructure solutions, such as pocket parks, are introduced more and more frequently. They improve the microclimate, provide comfort, and improve the aesthetics of the place. Parks that form a spatially coherent network turn out to be the most valuable for intensively developed city structures. Methods used in the study include literature research, secondary data analysis, area inventory, archival study analysis and plot ownership analysis. The studied area borders with four city parks, however, there is not enough public green space fulfilling recreational functions. The particular issue refers to how to ensure the adequate amount of greenery in densely built-up areas. The aim of the research is to present the possibility of introducing greenery in densely built-up districts of Lodz. The project of the pocket parks network for the analysed area was presented and method of green infrastructure implementation proposed.

Noise-resilient and high-speed deep learning with coherent silicon photonics

The explosive growth of deep learning applications has triggered a new era in computing hardware, targeting the efficient deployment of multiply-and-accumulate operations. In this realm, integrated photonics have come to the foreground as a promising energy efficient deep learning technology platform for enabling ultra-high compute rates. However, despite integrated photonic neural network layouts have already penetrated successfully the deep learning era, their compute rate and noise-related characteristics are still far beyond their promise for high-speed photonic engines. Herein, we demonstrate experimentally a noise-resilient deep learning coherent photonic neural network layout that operates at 10GMAC/sec/axon compute rates and follows a noise-resilient training model. The coherent photonic neural network has been fabricated as a silicon photonic chip and its MNIST classification performance was experimentally evaluated to support accuracy values of >99% and >98% at 5 and 10GMAC/sec/axon, respectively, offering 6× higher on-chip compute rates and >7% accuracy improvement over state-of-the-art coherent implementations.

Unequally spaced PAM-4 signaling enabled sensitivity enhancement of a simplified coherent receiver applied in a UDWDM-PON.

We experimentally demonstrate a 4 × 10 Gb/s cost-effective coherent ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) by the use of unequally-spaced 4-level pulse-amplitude modulation (UES-PAM-4) signaling. Because of the advantages of simple architecture and low cost, the simplified coherent receiver (SCR) based on the transmitted signal diversity (TS-D) has been reported, but its receiver sensitivity is constrained by the severe noise arising in the higher level of conventional PAM-4 signals. Here, we first experimentally demonstrate the UES-PAM-4 signaling for the SCR based on the TS-D, by altering the PAM-4 level spacing and the decision threshold through the gradient descent algorithm (GDA). Consequently, we can experimentally achieve -30.1 dBm RS for single wavelength at the bit-error ratio (BER) of 3.8 × 10-3. Compared with the conventional equally-spaced PAM-4 (ES-PAM-4) signaling, 1.3 dB RS enhancement can be secured after the 20-km standard single-mode fiber (SSMF) transmission. Meanwhile, the UES-PAM-4 signaling is experimentally verified for 4 × 10 Gb/s UDWDM-PON. An average RS of -29.6 dBm and 32.6 dB power budget are obtained after the 20-km SSMF transmission. The proposed UES-PAM-4 signaling with the RS enhancement is a promising candidate for the UDWDM-PON by utilizing the existing optical distribution network (ODN).

Bidirectional Symmetrical 100 Gb/s/λ Coherent PON Using a Simplified ONU Transceiver

In this letter, a bidirectional symmetric 100 Gb/s/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> coherent passive optical network (PON) scheme with a simplified optical network unit (ONU) transceiver is proposed and experimentally demonstrated. In the proposed scheme, the downstream signal is generated in a dual-polarization coherent transmitter with Alamouti-coding at the optical line terminal (OLT) side and then received by a single-polarization heterodyne receiver at the ONU side. The upstream signal is generated in a low-cost C-band electro-absorption modulated laser (EML) at the ONU side and then received by a standard dual-polarization integrated coherent receiver at the OLT side. The experimental results show that more than 30 dB power budget is achieved after 25 km standard single mode fibre transmission for both downstream and upstream signal at 100 Gb/s/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> . The cost at the ONU side is maintained low as the required bandwidth of the optoelectrical device is >25 GHz and the local oscillator power at the ONU side can be as low as 4 dBm.

Self-healing WDM-based point-to-multipoint coherent passive optical network system with ONU-collaborative star topology for access-span robustness.

This study proposed a new small star topology network architecture connecting a secondary fiber link between adjacent small cell base stations for disaster tolerance in the access span of a short-reach point-to-multipoint optical communication system. Compared to the edge-side optical node independent architecture, the proposed network architecture exhibits a high robustness and small number of optical components. We compared the conventional and proposed configurations for survivability in the case of a major disaster with a triple-link failure. The proposed method made it easy to add a small star-shaped network with secondary links for significant edge-side optical nodes while maintaining the basic configuration of the conventional passive optical network.

An ALE meta-analytic review of musical expertise

Through long-term training, music experts acquire complex and specialized sensorimotor skills, which are paralleled by continuous neuro-anatomical and -functional adaptations. The underlying neuroplasticity mechanisms have been extensively explored in decades of research in music, cognitive, and translational neuroscience. However, the absence of a comprehensive review and quantitative meta-analysis prevents the plethora of variegated findings to ultimately converge into a unified picture of the neuroanatomy of musical expertise. Here, we performed a comprehensive neuroimaging meta-analysis of publications investigating neuro-anatomical and -functional differences between musicians (M) and non-musicians (NM). Eighty-four studies were included in the qualitative synthesis. From these, 58 publications were included in coordinate-based meta-analyses using the anatomic/activation likelihood estimation (ALE) method. This comprehensive approach delivers a coherent cortico-subcortical network encompassing sensorimotor and limbic regions bilaterally. Particularly, M exhibited higher volume/activity in auditory, sensorimotor, interoceptive, and limbic brain areas and lower volume/activity in parietal areas as opposed to NM. Notably, we reveal topographical (dis-)similarities between the identified functional and anatomical networks and characterize their link to various cognitive functions by means of meta-analytic connectivity modelling. Overall, we effectively synthesized decades of research in the field and provide a consistent and controversies-free picture of the neuroanatomy of musical expertise.

Photonics-enabled distributed MIMO radar for high-resolution 3D imaging

Three-dimensional (3D) imaging radar is an advanced sensor applied in space surveillance and target recognition for supplying 3D geometric features and supporting visualization. However, high 3D resolution requires both broadband operation and a large 2D aperture, which are difficult and complex for conventional radars. This paper presents a photonics-enabled distributed multiple-input and multiple-output (MIMO) radar with a centralized architecture. By use of photonic multi-dimensional multiplexing, multi-channel signal generation and reception are implemented on a shared reference signal in a central office, enabling a highly coherent network with a simple structure. Additionally, a sparse array and a synthetic aperture are combined to efficiently reduce the required transceivers, further weakening the dilemma between system complexity and angular resolution. A 4 × 4 MIMO radar is established and evaluated in field tests. A high-resolution 3D image of a non-cooperative aircraft is obtained, in which rich details are displayed. From a comparison with electronics-based radar, significant resolution improvement is observed. The results verify the superior imaging capability and practicability of the proposed radar and its great potential to outperform conventional technologies in target classification and recognition applications.