Many Applications In Telecommunications Research Articles

Modeling and control of a reconfigurable photonic circuit using deep learning

The complexity of experimental quantum information processing devices is increasing rapidly, requiring new approaches to control them. In this paper, we address the problems of practically modeling and controlling an integrated optical waveguide array chip—a technology expected to have many applications in telecommunications and optical quantum information processing. This photonic circuit can be electrically reconfigured, but only the output optical signal can be monitored. As a result, the conventional control methods cannot be naively applied. Characterizing such a chip is challenging for three reasons. First, there are uncertainties associated with the Hamiltonian model describing the chip. Second, we expect distortions of the control voltages caused by the chip’s electrical response, which cannot be directly observed. And third, there are imperfections in the measurements caused by losses from coupling the chip externally to optical fibers. We have developed a deep neural network (NN) approach to solve these problems. The architecture is designed specifically to overcome the aforementioned challenges using a gated recurrent unit -based network as the central component. The Hamiltonian is estimated as a blackbox, while the rules of quantum mechanics such as state evolution is embedded in the structure as a whitebox. The resulting overall graybox model of the chip shows good performance both quantitatively in terms of the mean square error and qualitatively in terms of the shape of the predicted waveforms We use this NN to solve a classical and a quantum control problem. In the classical application we find a control sequence to approximately realize a time-dependent output power distribution. For the quantum application we obtain the control voltages to realize a target set of quantum gates. The method we propose is generic and can be applied to other systems that can only be probed indirectly.

Set Aside when Building the Periodic Table 150 Years ago, are Rare Earths any better considered by Chemists in the 21st Century?

A hundred and fifty years ago, the Rare Earths posed a serious problem to Mendeleyev because of their very similar chemical properties, although their atomic mass dispersions pointed to different elements. This difficulty persisted for several decades and only the emergence of the atomic theory provided some legiti- macy for their consideration as a full series of 15 elements resulting from the filling of the 4f orbitals (La-4f0 to Lu-4f14 ), to which scandium and yttrium were added for the sake of chemical similarities. However, it is difficult to give up bad habits and major advances in transition metal chemistry started systematically with d-block cations prior to extension to f-block analogues, and this despite the broader perspectives often brought by the latter. The technology-oriented society put in place for economic reasons during the last five decades has reactivated scientific interest in the Rare Earths, which have now become essential for many applications in telecommunications, lasers, magnetic materials and optical devices.

Automatic Configuration and Wavelength Locking of Coupled Silicon Ring Resonators

Coupled silicon ring resonator filters offer high-order spectral features such as steep roll-offs, high extinction ratios, and wide pass-bands, which are attractive to many applications in telecommunications and quantum computing systems. However, so far, their sensitivity to fabrication and temperature variations have limited the usability of such filters in practical applications. Here, by using in-resonator photoconductive heaters (IRPHs) to both sense and tune the resonance conditions of ring resonators, we demonstrate automatic configuration and wavelength locking of multiring resonator filters to an input laser's wavelength. We demonstrate the automatic configuration of a four-ring Vernier filter across a 36.7-nm wavelength range spanning the entire C-band and the wavelength locking of the same filter to counteract a practical chip temperature variation of 65 ${^\circ }$ C. As IRPHs do not require additional material depositions, photodetectors, or power taps and use the same contact pads for both the sense and the tune operations, these results are achieved without compromising the cost or area of the devices. Furthermore, by localizing the feedback loops to only rely on the resonance conditions of adjacent rings, we present a tuning algorithm in which the number of iterations scales linearly with the number of coupled rings in the system. As this method does not rely on the output spectral shape of the system, it is, in general, applicable to a wide range of coupled resonator systems. Our results pave a path toward practical deployment of high-order and large-scale silicon ring resonator systems.

Erbium‐doped integrated waveguide amplifiers and lasers

AbstractErbium‐doped fiber devices have been extraordinarily successful due to their broad optical gain around 1.5–1.6 µm. Er‐doped fiber amplifiers enable efficient, stable amplification of high‐speed, wavelength‐division‐multiplexed signals, thus continue to dominate as part of the backbone of longhaul telecommunications networks. At the same time, Er‐doped fiber lasers see many applications in telecommunications as well as in biomedical and sensing environments. Over the last 20 years significant efforts have been made to bring these advantages to the chip level. Device integration decreases the overall size and cost and potentially allows for the combination of many functions on a single tiny chip. Besides technological issues connected to the shorter device lengths and correspondingly higher Er concentrations required for high gain, the choice of appropriate host material as well as many design issues come into play in such devices. In this contribution the important developments in the field of Er‐doped integrated waveguide amplifiers and lasers are reviewed and current and future potential applications are explored. The vision of integrating such Er‐doped gain devices with other, passive materials platforms, such as silicon photonics, is discussed.

Continuity of Optimal Values and Solutions for Control of Markov Chains with Constraints

We consider in this paper constrained Markov decision processes. This type of control model has many applications in telecommunications and other fields [E. Altman and A. Shwartz, IEEE Trans. Automat. Control, 34 (1989), pp. 1089--1102, E. A. Feinberg and M. I. Reiman, Probab. Engrg. Inform. Sci., 8 (1994), pp. 463--489, A. Hordijk and F. Spieksma, Adv. in Appl. Probab., 21 (1989), pp. 409--431, A. Lazar, IEEE Trans. Automat. Control, 28 (1983), pp. 1001--1007, P. Nain and K. W. Ross, IEEE Trans. Automat. Control, 31 (1986), pp. 883--888, K. W. Ross and B. Chen, IEEE Trans. Automat. Control, 33 (1988), pp. 261--267]. We address the issue of the convergence of the value and optimal policies of the problem with discounted costs, to the ones for the problem with expected average cost. We consider the general multichain ergodic structure. We present two stability results in this paper. We establish the continuity of optimal values and solutions of as well as some type of robustness of some suboptimal solutions in the discount factor. Our proof relies on same general theory on continuity of values and solutions in convex optimization that relies on well-known notions of $\Gamma$-convergence.

Bicriteria network design using a spanning tree-based genetic algorithm

The optimization problems in communication networks have received the attention of many researchers in such related fields as network designer, network analysis, and network administration. The use of computer communication networks has been increasing rapidly in order to share expensive hardware/software resources and provide access to main systems from distant locations. These network problems have many applications in telecommunications, computer networking, and related domains in electric, gas, and sewer networks. In computer networking, LANs (local area networks) are commonly used as the communication infrastructure that meets the demands of users in the local environment. These networks typically consist of several LAN segments connected together via bridges. The use of these transparent bridges requires.loop-free paths between LAN segments. Therefore, only spanning tree topologies can be used as active LAN configurations. Recently, genetic algorithms have greatly advanced in related research fields such as network optimization problems, combinatorial optimization, multiobjective optimization, and so on. Genetic algorithms have also received a great deal of attention because of their ability as optimization techniques for many real-world problems. In this paper, we attempt to solve the LAN topology design problem with bicriteria which minimize the cost and average message delay using genetic algorithms, and propose a method of searching the Pareto solutions. We also employ the Prufer number in order to represent the chromosomes, because the interconnection between the network service centers must yield spanning tree configurations. Finally, we conduct experiments to certify the quality of the networks designs obtained by using genetic algorithms.

A queueing model for an ATM rate control scheme

Many applications in telecommunications engineering lead to highly degenerate partitioned Markov chains of QBD type. In this paper, we study a traffic shaping scheme which is based on a generalization of the bucket method. The arrival process is modeled by a discrete Markovian arrival process. For this model, a detailed mathematical analysis leads to special algorithms involving matrices of lower order. The characteristics of the model are discussed from this viewpoint. Some performance measurements are derived and numerical examples are shown to demonstrate the effectiveness of the rate control scheme.

Some results on broad-band microstrip antenna with low cross polar and high gain

Stacked square microstrip broadband antennas with low cross polarization and high gain are studied. The low cross polarization is mainly due to the location of excitation feeds on the diagonals of the square lower patch. These advantages are explained in comparison with the usual case in which the excitation is positioned along the median. The evolution of one of the principal antenna parameters is studied by the spectral domain approach. A stacked antenna is realized on a low-loss substrate, and experimental results are compared with theory. The good performance obtained, even for linear polarization, shows that this antenna can be used in many applications in telecommunications. >