A Machine Learning-based Framework for Predictive Maintenance of Semiconductor Laser for Optical Communication

Semiconductor lasers, one of the key components for optical communication systems, have been rapidly evolving to meet the requirements of next generation optical networks with respect to high speed, low power consumption, small form factor etc. However, these demands have brought severe challenges to the semiconductor laser reliability. Therefore, a great deal of attention has been devoted to improving it and thereby ensuring reliable transmission. In this paper, a predictive maintenance framework using machine learning techniques is proposed for real-time heath monitoring and prognosis of semiconductor laser and thus enhancing its reliability. The proposed approach is composed of three stages: i) real-time performance degradation prediction, ii) degradation detection, and iii) remaining useful life (RUL) prediction. First of all, an attention based gated recurrent unit (GRU) model is adopted for real-time prediction of performance degradation. Then, a convolutional autoencoder is used to detect the degradation or abnormal behavior of a laser, given the predicted degradation performance values. Once an abnormal state is detected, a RUL prediction model based on attention-based deep learning is utilized. Afterwards, the estimated RUL is input for decision making and maintenance planning. The proposed framework is validated using experimental data derived from accelerated aging tests conducted for semiconductor tunable lasers. The proposed approach achieves a very good degradation performance prediction capability with a small root mean square error (RMSE) of 0.01, a good anomaly detection accuracy of 94.24% and a better RUL estimation capability compared to the existing ML-based laser RUL prediction models.Comment: Published in Journal of Lightwave Technology (Volume: 40, Issue: 14, 15 July 2022

Fault Monitoring in Passive Optical Networks using Machine Learning Techniques

Passive optical network (PON) systems are vulnerable to a variety of failures, including fiber cuts and optical network unit (ONU) transmitter/receiver failures. Any service interruption caused by a fiber cut can result in huge financial losses for service providers or operators. Identifying the faulty ONU becomes difficult in the case of nearly equidistant branch terminations because the reflections from the branches overlap, making it difficult to distinguish the faulty branch given the global backscattering signal. With increasing network size, the complexity of fault monitoring in PON systems increases, resulting in less reliable monitoring. To address these challenges, we propose in this paper various machine learning (ML) approaches for fault monitoring in PON systems, and we validate them using experimental optical time domain reflectometry (OTDR) data.Comment: ICTON 202

Degradation Prediction of Semiconductor Lasers using Conditional Variational Autoencoder

Semiconductor lasers have been rapidly evolving to meet the demands of next-generation optical networks. This imposes much more stringent requirements on the laser reliability, which are dominated by degradation mechanisms (e.g., sudden degradation) limiting the semiconductor laser lifetime. Physics-based approaches are often used to characterize the degradation behavior analytically, yet explicit domain knowledge and accurate mathematical models are required. Building such models can be very challenging due to a lack of a full understanding of the complex physical processes inducing the degradation under various operating conditions. To overcome the aforementioned limitations, we propose a new data-driven approach, extracting useful insights from the operational monitored data to predict the degradation trend without requiring any specific knowledge or using any physical model. The proposed approach is based on an unsupervised technique, a conditional variational autoencoder, and validated using vertical-cavity surface-emitting laser (VCSEL) and tunable edge emitting laser reliability data. The experimental results confirm that our model (i) achieves a good degradation prediction and generalization performance by yielding an F1 score of 95.3%, (ii) outperforms several baseline ML based anomaly detection techniques, and (iii) helps to shorten the aging tests by early predicting the failed devices before the end of the test and thereby saving costsComment: Published in: Journal of Lightwave Technology (Volume: 40, Issue: 18, 15 September 2022

Incidence and developmental timing of endosperm failure in post-zygotic isolation between wild tomato lineages

Background and AimsDefective hybrid seed development in angiosperms might mediate the rapid establishment of intrinsic post-zygotic isolation between closely related species. Extensive crosses within and among three lineages of wild tomatoes (Solanum section Lycopersicon) were performed to address the incidence, developmental timing and histological manifestations of hybrid seed failure. These lineages encompass different, yet fairly recent, divergence times and both allopatric and partially sympatric pairs.MethodsMature seeds were scored visually 2 months after hand pollinations, and viable-looking seeds were assessed for germination success. Using histological sections from early-developing seeds from a sub-set of crosses, the growth of three major seed compartments (endosperm, embryo and seed coat) was measured at critical developmental stages up to 21 d after pollination, with a focus on the timing and histological manifestations of endosperm misdevelopment in abortive hybrid seeds.Key ResultsFor two of three interspecific combinations including the most closely related pair that was also studied histologically, almost all mature seeds appeared ‘flat’ and proved inviable; histological analyses revealed impaired endosperm proliferation at early globular embryo stages, concomitant with embryo arrest and seed abortion in both cross directions. The third interspecific combination yielded a mixture of flat, inviable and plump, viable seeds; many of the latter germinated and exhibited near-normal juvenile phenotypes or, in some instances, hybrid necrosis and impaired growth.ConclusionsThe overall results suggest that near-complete hybrid seed failure can evolve fairly rapidly and without apparent divergence in reproductive phenology/biology. While the evidence accrued here is largely circumstantial, early-acting disruptions of normal endosperm development are most probably the common cause of seed failure regardless of the type of endosperm (nuclear or cellular)

Vocal Interactivity in-and-between Humans, Animals, and Robots

Almost all animals exploit vocal signals for a range of ecologically motivated purposes: detecting predators/prey and marking territory, expressing emotions, establishing social relations, and sharing information. Whether it is a bird raising an alarm, a whale calling to potential partners, a dog responding to human commands, a parent reading a story with a child, or a business-person accessing stock prices using Siri, vocalization provides a valuable communication channel through which behavior may be coordinated and controlled, and information may be distributed and acquired. Indeed, the ubiquity of vocal interaction has led to research across an extremely diverse array of fields, from assessing animal welfare, to understanding the precursors of human language, to developing voice-based human–machine interaction. Opportunities for cross-fertilization between these fields abound; for example, using artificial cognitive agents to investigate contemporary theories of language grounding, using machine learning to analyze different habitats or adding vocal expressivity to the next generation of language-enabled autonomous social agents. However, much of the research is conducted within well-defined disciplinary boundaries, and many fundamental issues remain. This paper attempts to redress the balance by presenting a comparative review of vocal interaction within-and-between humans, animals, and artificial agents (such as robots), and it identifies a rich set of open research questions that may benefit from an interdisciplinary analysis

From the "planning euphoria" to the "bitter economic truth": The transmission of economic ideas into German labour market policies in the 1960s and 2000s

This paper compares the interconnections between dominant economic thought and processes of policy-making in the area of labour market reforms in Germany in the late 1960s and the early 2000s. The transition in labour market policies in this period could be described as a change from an active to an activating approach. At the level of economic discourse these policy changes correspond to a paradigm shift from Keynesian to neoclassical/neoliberal economic thought. We investigated these changes by focussing on two distinct reforms of labour market policies and carried out a critical discourse analysis of the relevant public and academic discourse of economists. We find that the paradigm shift in economic thought was accompanied by a shift in economists' discourses on labour market policy issues

Has economics returned to being the 'dismal science'? The changing role of economic thought in German labour market reforms

As an immediate reaction to the recent financial crisis, it has been criticized that many economists are still acting as economic advisers for Ministries or the bureaucracy, although they have not been able to foresee the crisis . Academic economists still hold central positions in policy making; they influence decisions in economic expert panels or research departments in national and supranational organizations. Beside their role as policy advisors, economists also engage in public debates in a more narrow sense as technical economic experts as well as in a broader sense as "public intellectuals" in the process of the tra nsmission of economic knowledge in public (economic) policy discourses. In spite of the manifold critique about the state of economics in the aftermath of the crisis, an even increasing presence of economists and economic experts can be observed in the pu blic sphere during the last years . On the one hand this reflects the still dominant position of economics in the social sciences as well as the sometimes ignorant attitude of economists towards findings of other social sciences. On the other hand this pape r shows that the public debate on politico - economic issues among economists is dominated by a specific sub group of economists, tightly connected to an institutional network of "German neoliberalism". This group of "public economists" (i) is dominant in pub lic debates even after the financial crisis, (ii) reproduces the formative German economic imaginary of the Social Market Economy in a German neoliberal interpretation and (iii) has a good access to German economic policymaking, rooted in a long history of economic policy advice

Zwischen Meritokratie und Wohlfahrtschauvinismus

Die im Dezember 2017 angelobte ÖVP/FPÖ-Koalition formulierte in ihrem Regierungsprogramm weitreichende Reformvorhaben im Bereich der Arbeitsmarkt- und Sozialpolitik. Während die Umsetzung vieler dieser Vorhaben am vorzeitigen Ende der Regierung im Mai 2019 scheiterte, erfuhren andere eine Realisierung. Im Rahmen des Papers wollen wir uns mit drei dieser Reformen in der Arbeitszeitpolitik ("Zwölfstundentag"), Arbeitsmarktpolitik (Sistierung der "Aktion 20.000") sowie Sozialhilfepolitik (Sozialhilfe-Grundsatzgesetz) beschäftigen. Den Hintergrund dafür bildet die Debatte um sogenannte Populist Radical Right (PRR)-Parteien und ihr sozial- und arbeitsmarktpolitisches Profil beim Eintritt in eine Koalitionsregierung mit bürgerlich-wirtschaftsliberalen Parteien. Besagter Debatte zufolge stehen PRR-Parteien in diesem Kontext nämlich vor dem Dilemma, "whom to betray" (Alexandre Afonso) - ihre (i.d.R. "Sozialstaats-kritischen") Koalitionspartner oder ihre (i.d.R. "Sozialstaats-affinen") WählerInnen. Vor diesem Hintergrund fragen wir danach, welche theoretisch abgeleiteten Deutungsrahmen bzw. Frames in der medialen Debatte um die angesprochenen Reformen eine Rolle spielen: Wie werden also auf Regierungsseite, aber auch aufseiten oppositioneller Kräfte die angesprochenen Reformen diskursiv gerahmt, welche konkreten AkteurInnen bzw. Diskurskoalitionen treten medial in Erscheinung und wo verlaufen die zentralen Konfliktlinien in den Diskussionen um eine Reform der Sozial- und Arbeitsmarktpolitik? Um diese Fragen zu beantworten wurde in softwaregestützter Form (MAXQDA) eine kritische Diskursanalyse der medialen Debatten zu den dargelegten Reformen durchgeführt. Dabei fokussierten wir auf drei österreichische Tageszeitungen (Der Standard, Die Presse, Neue Kronen Zeitung) im Zeitraum zwischen Dezember 2017 und Mai 2019. Im Ergebnis zeigt sich, dass die diskursive Rahmung in den drei Politikfeldern weitreichende Differenzen aufweist: Während der Regierungsdiskurs in der Sozialhilfepolitik etwa zentral durch nativistische und autoritäre Frames bestimmt ist, dominieren in der Arbeitsmarktpolitik stärker neoliberale Frames, welche die Unzulänglichkeiten staatlicher Steuerungsprozesse kritisieren und ihr die behauptete Effizienz des Marktes entgegenstellen. Wie dargelegt wird, verweisen diese divergierenden Deutungsrahmen auf unterschiedliche Legitimationsformen, mit deren Hilfe die Reformen gegenüber verschiedenen AkteurInnen begründet und gerechtfertigt werden sollen

Incidence and developmental timing of endosperm failure in post-zygotic isolation between wild tomato lineages

Abstract Background and Aims Defective hybrid seed development in angiosperms might mediate the rapid establishment of intrinsic post-zygotic isolation between closely related species. Extensive crosses within and among three lineages of wild tomatoes (Solanum section Lycopersicon) were performed to address the incidence, developmental timing and histological manifestations of hybrid seed failure. These lineages encompass different, yet fairly recent, divergence times and both allopatric and partially sympatric pairs. Methods Mature seeds were scored visually 2 months after hand pollinations, and viable-looking seeds were assessed for germination success. Using histological sections from early-developing seeds from a sub-set of crosses, the growth of three major seed compartments (endosperm, embryo and seed coat) was measured at critical developmental stages up to 21 d after pollination, with a focus on the timing and histological manifestations of endosperm misdevelopment in abortive hybrid seeds. Key Results For two of three interspecific combinations including the most closely related pair that was also studied histologically, almost all mature seeds appeared ‘flat' and proved inviable; histological analyses revealed impaired endosperm proliferation at early globular embryo stages, concomitant with embryo arrest and seed abortion in both cross directions. The third interspecific combination yielded a mixture of flat, inviable and plump, viable seeds; many of the latter germinated and exhibited near-normal juvenile phenotypes or, in some instances, hybrid necrosis and impaired growth. Conclusions The overall results suggest that near-complete hybrid seed failure can evolve fairly rapidly and without apparent divergence in reproductive phenology/biology. While the evidence accrued here is largely circumstantial, early-acting disruptions of normal endosperm development are most probably the common cause of seed failure regardless of the type of endosperm (nuclear or cellular)

Performance Comparison of Single-Sideband Direct Detection Nyquist-Subcarrier Modulation and OFDM

Direct detection transceivers offer advantages, including low cost and complexity, in short- and medium-haul links. We carried out studies seeking to identify the signal formats which offer the highest information spectral densities and maximum transmission distances for direct detection links. The performance of two spectrally efficient optical signal formats, single-sideband (SSB) Nyquist pulse-shaped subcarrier modulation (SCM) and SSB orthogonal frequency-division multiplexing (OFDM), are compared by means of simulations. The comparison is performed for a range of wavelength-division multiplexing (WDM) net information spectral densities up to 2.0 b/s/Hz by varying the signal bandwidth, modulation cardinality, and WDM channel spacing. The signal formats' tolerance to signal-signal beating interference, resulting from square-law detection, is investigated, and the Nyquist-SCM format is found to suffer lower penalties from this nonlinearity at high information spectral densities. In 7 × 28 Gb/s WDM transmission at 2.0 b/s/Hz (with electronic predistortion and EDFA-only amplification), Nyquist-SCM signals can be transmitted over distances of up to 720 km of standard SMF in comparison to a maximum of 320 km with the OFDM signal format