1,721,033 research outputs found
Optimum Symbol Distribution of Probabilistically Shaped PAM Signals in Amplifier-less IM-DD Systems
No full textWe present an explicit-form expression of the optimum symbol distribution of N-ary pulse amplitude modulated signals for capacity in intensity-modulation/direct-detection systems under peak-power constraint condition. Its validity is confirmed through Monte-Carlo simulation
Capacity-achieving symbol distributions for directly modulated laser and direct detection systems
No full textWe investigate the capacity-achieving symbol distributions for directly modulated laser (DML) and direct-detection (DD) systems utilizing probabilistic constellation shaped pulse amplitude modulation formats. DML-DD systems utilize a bias tee to feed the DC bias current and AC-coupled modulation signals. Also, an electrical amplifier is commonly utilized to drive the laser. Thus, most DML-DD systems are subject to the constraints of the average optical power and peak electrical amplitude. We compute the channel capacity of the DML-DD systems under these constraints by using the Blahut-Arimoto algorithm to obtain the capacity-achieving symbol distributions. We also carry out experimental demonstration to verify our computation results. We show that the probabilistic constellation shaping (PCS) technique marginally increases the capacity of DML-DD system when the optical modulation index (OMI) is less than 1. However, the PCS technique allows us to increase the OMI larger than 1 without clipping distortions. As a result, we can increase the capacity of DML-DD system by using the PCS technique in comparison with the uniformly distributed signals.
Low-Complexity, Loop-Unrolled Decision-Feedback Equalizer for IM/DD System Using PAM Formats
No full textWe propose and demonstrate a low-complexity, loop-unrolled DFE for band-limited IM/DD system. The proposed equalizer nearly doubles the maximum achievable data-rate of DFE for PAM-4 signal, but requires complexity similar to that of NRZ DFE. © 2021 OSA
Generation of Broadband Optical SSB Signal Using Dual Modulation of DML and EAM
No full textThe dual modulation transmitter, where both the directly modulated laser (DML) and electro-absorption modulator (EAM) are modulated, has attracted considerable attention due to its monolithic integration and high output power. This transmitter is capable of manipulating the optical intensity and phase independently since the DML and EAM serve mainly as phase and intensity modulators, respectively. Thus, the dual modulation scheme has been used to generate optical single sideband (SSB) signals. However, due to a lack of workable model applicable to high modulation frequency (e.g., >10 GHz), the data rates of optical SSB signals reported previously were all limited to <= 40 Gb/s. In this paper, we generate a 120-Gb/s optical SSB orthogonal frequency-division multiplexed (OFDM) signal using the dual modulation scheme. By using the time-harmonic model of dual modulation we have recently reported, we establish a generation procedure for broadband optical SSB signals, where the modulation conditions for DML and EAM are provided. In order to satisfy these conditions over a broad frequency range, we also propose (1) utilizing the frequency-modulation discriminator to measure the DML's chirp characteristics and (2) pre-compensating for the frequency responses of DML and EAM. In our experimental verification, we generate the 120-Gb/s SSB OFDM signal having an optical sideband suppression ratio of 19 dB. We also successfully transmit this signal over 80 km long standard single-mode fiber.
Operations Research Helps the Optimal Bidding of Virtual Power Plants
No full textAs distributed energy resources (DERs) continue to emerge, a new cloud-based information technology platform business model, the virtual power plant (VPP), is being introduced into the electricity market. The competitiveness of VPPs mainly depends on data analytics and operational technologies. Among the several operational problems, we focus on the optimal bidding decision problem in the day-ahead market. The bidding decision is a VPP???s commitment to supply the market with electricity from uncertain DERs, thereby affecting the VPP???s profits. Based on a collaboration with a VPP company in South Korea, H Energy Co. Ltd., we formulate a Markov decision process model for the problem and use a stochastic dynamic programming-based solution approach. This is the first study under the incentivebased market structure. To describe the uncertainty in the power supply from DERs, we build frameworks to generate scenario trees or lattices. Additionally, we apply heuristic techniques to reduce the computational burden. Through a pilot test based on real data, we verify the performance and practicality of our proposed model and solution approach. The case company has begun implementing the model and solution approach on its platform and has found that performance has improved after using advanced forecasting models for DERs.11Nsciessc
3D-printed electronics for biomedical applications
No full textBiomedical electronics have garnered significant interest due to the rising demand for advanced healthcare devices for diagnosis, monitoring, and treatment. Threedimensional (3D) printing, or additive manufacturing, has emerged as an attractive fabrication method for developing these advanced biomedical devices. Its unique features, such as versatility, cost-effectiveness, and rapid prototyping capabilities, when combined with medical imaging technologies enable the creation of highly precise and customized patient-specific structures. Extensive research in the field of 3D printing has focused on developing biomedical devices, including wearable and implantable devices, as well as scaffolds or platforms. Recently, the integration of 3D printing with state-of-the-art electronic materials, known for their high flexibility, conductivity, stretchability, stability, and biocompatibility, has led to the development of innovative biomedical electronics. In this review, we outline the recent advancements in 3D printing technologies and their applications in bioelectronic devices. Firstly, we describe various 3D printing methods and printable electronic materials, highlighting their advantages and limitations. Subsequently, we explore the applications of these technologies in biomedical research, spanning from surgical guidance and prosthetics to health monitoring devices and tissueengineered scaffolds. Finally, this review discusses the current challenges and future directions to fully exploit the potential of 3D-printed bioelectronic devices, aimed at transforming personalized healthcare.
80-km Reach 28-Gb/s/λ RSOA-based Coherent WDM PON Using Dither-Frequency-Tuning SBS Suppression Technique
No full textWe experimentally demonstrate 80-km transmission of 28-Gb/s QPSK signal in loopback-configured coherent WDM PON using RSOAs. Dither frequency is tuned to suppress the SBS and minimize the adverse effect of broadened linewidth on carrier phase estimation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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