The article presents a spectral analysis of the transmission coefficient of an optical fiber in the event of short attenuation jumps. In this case, it is assumed that the time function of the additional loss factor is a symmetrical triangular function with the same rise and fall times. It is shown that the spectral loss density is sensitive to the number of attenuation jumps, has a low-frequency character and has a filtering effect on the useful signal. Approaches to the analysis of performance characteristics of fiber-optic transmission systems under specific operating conditions are considered.
The telecommunication systems development based on single-mode and multimode optical fibers is aimed at the rapidly increasing demand for bandwidth not only transport networks, but also intra-site data centers networks, cloud computing, and web servers. The solution to this problem is provided by the signal processing technologies complexity. In this case, the requirements for the receiver complexity can be reduced by using technologies to combat signal distortion due to equalizers together with FEC. There was known that the use of FEC based on permutation decoding in relation to the RS codes provides a significant gain in the data processing speed by the receiver due to the use of a cognitive procedure for searching the generating matrix of the equivalent code. The paper shows that the use of this technology can be successful in solving another important task related to minimizing the timing attacks consequences on the protection confidential information system. This is due to the active development of quantum computers and the problems of post-quantum cryptography that arose on this basis. The essence of leveling the timing attacks risks is to equalize the time spent on processing vectors of redundant BCH or RS codes. The use of permutation decoding fully matches these requirements by replacing the algebraic system of detection and errors correction in the data on the procedure of lexicographic search for the desired result. It is shown that the data processing time when using permutation decoding in conjunction with the cognitive search for the decoding result varies slightly.
A method of improving the performance of non-binary redundant code decoders in a coherent network system using forward error correction is considered. It is proposed to use permutation decoding which in contrast to the known methods of processing error-correcting codes has a number of deterministic parameters. Such parameters in the procedure of decoding code vectors can be determined in advance and included in the cognitive map of the decoder. The using of cognitive map data dramatically reduces the amount of matrix calculations in the permutation decoding of system, which contributes to the performance of the decoder. This contributes to the harmonization of high-speed data flow to the input of the decoder of the optical system on the physical level with relatively limited processing capabilities of the processors on the data link layer. The methods of reducing the memory size of the cognitive map of such decoder and fast search of reference matrices of equivalent codes through the use of lexicographic navigation are considered.
The fiber optic communication systems are the basis for ensuring global communication of the modern society. High bandwidth and low noise are the main advantages of the indicated class of communication systems. Nevertheless, fiber optic communication systems have a series of confounding factors arising because of the temporary operation, and due to the used fiber optic cable. To compensate for such manifestations it is necessary to use modern error-correcting codes and their decoding methods. In the work proposed to use polar codes and the lexicographic method of decoding.
The main advantages of polar codes are the ability to achieve bandwidth, binary symmetric channel of communication, high adaptation to the end-user and acceptable level of correcting capabilities. In the based lexicographic approach is the method of clustering of the space of allowed codewords. Technology of division clusters or lexicographic ordering of the space of allowed codewords of error-correcting binary block codes implements non-algebraic approach to the processing of code vectors of the receiver, allowing to reduce the computation cost and to provide energy gain.
KEYWORDS: Error analysis, Receivers, Signal to noise ratio, Interference (communication), Signal detection, Statistical analysis, Signal processing, Photodetectors, Telecommunications, Nonlinear optics
The problems of statistical analysis of a typical receive optical module (TROM) in the detection of a random optical signal and the synthesis of an optimal algorithm for discrimination of the optical signals in a binary communication system are solved in a paper. The envelope of optical field intensity is described by the Nakagami distribution density. Conditional Poisson distribution of the photoelectron counts and its asymptotic approximation, during limitation of the detection process by thermal noise is obtained. Statistical model of the signal and noise mixture at the TROM output consider the dynamic range of optical signal. The synthesis of the Bayesian algorithm for signals discrimination is performed taking into account the restrictions imposed by the preset TROM structure. The average error probability of signals discrimination is estimated. Conditions for feasibility of the synthesized algorithm are discussed.
The expression for electron count optimal threshold value has been obtained in the article, the expression for evaluation of potentially achievable average error probability value during binary signals differentiation by an optical receiver with consideration of synchronization error has been refined. It has been shown that a time interval error switches the receiver into a mode that does not provide minimal average error probability. This explains a significant increase in error probability, which is mostly caused by errors during transmissions of “zeros” due to a lowered count threshold value. The obtained results enable us to determine synchronization error exchange conditions on optical signal power with a predetermined average error probability value, and to substantiate synchronization precision tolerances.
The analytical expression for probability distribution density of transmission coefficient for passive linear channel of fiber-optic systems functioning under the influence of mechanical load has been obtained in the research. It has been shown that probability distribution density is sensitive to the amount of fiber microcracks and the amount of fading on each of them, and also includes the parameters that are determined by the optical fiber drawing technology.
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