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Proceedings of the IEEE

Issue 8 • Date Aug 1990

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Displaying Results 1 - 4 of 4
  • Performance of coherent optical receivers

    Publication Year: 1990 , Page(s): 1369 - 1394
    Cited by:  Papers (55)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1952 KB)  

    Coherent optical communications, an area of research that shows great promise for future high-bandwidth and long-haul applications, is reviewed. Coherent optical receivers, which add light to the received signal as part of the detection process, have numerous advantages over direct-detection receivers, most notably increased sensitivity and increased selectivity, at the cost of increased complexity. The performance of coherent optical receivers under shot-noise-limited conditions is reviewed for a variety of modulation and demodulation formats. In addition, laser phase noise is discussed, and its effect on receiver performance is analyzed View full abstract»

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  • Formal methods for generating protocol conformance test sequences

    Publication Year: 1990 , Page(s): 1317 - 1326
    Cited by:  Papers (20)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (884 KB)  

    The four major methods of conformance test generation reported in the literature are reviewed: transition tours; distinguishing sequences; characterizing sequences; and unique input/output sequences. These methods are used to test the control portion of a protocol specification. The conformance testing concepts developed in the standards world are summarized. Their relationship with the four formal methods is discussed View full abstract»

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  • Nonlinear effects in coherent multichannel transmission through optical fibers

    Publication Year: 1990 , Page(s): 1344 - 1368
    Cited by:  Papers (14)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2144 KB)  

    Various nonlinear optical interactions in single-mode fibers that are used in coherent FDM (frequency division multiplexed) transmission systems are examined. It is these nonlinearities that lead to crosstalk between channels, power losses, and deleterious fluctuations, which in turn limit the power of the transmitted light and the number of allowed channels, and dictate the channel allocations. It is shown that, for long-haul transmission systems with fiber lengths exceeding 100 km, typical channel separation of 10 GHz, and few channels, the maximum allowed input power per channel, Pmax, is limited by SBS (stimulated Brillouin scattering) to about 5 dBm. As the number of channels increases, FWM (four wave mixing) becomes the limiting process with Pmax of about -5 dBm, whereas above several hundred channels SRS (stimulated Raman scattering) becomes dominant with Pmax of about -5 dBm. For local area networks with shorter lengths, the results are similar, except that the values of Pmax are uniformly higher by about 5 dB View full abstract»

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  • Tracking a few extreme singular values and vectors in signal processing

    Publication Year: 1990 , Page(s): 1327 - 1343
    Cited by:  Papers (202)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1212 KB)  

    In various applications it is necessary to keep track of a low-rank approximation of a covariance matrix, R(t), slowly varying with time. It is convenient to track the left singular vectors associated with the largest singular values of the triangular factor, L(t), of its Cholesky factorization. These algorithms are referred to as square-root. The drawback of the eigenvalue decomposition (EVD) or the singular value decompositions (SVD) is usually the volume of the computations. Various numerical methods for carrying out this task are surveyed, and it is shown why this heavy computational burden is questionable in numerous situations and should be revised. Indeed, the complexity per eigenpair is generally a quadratic function of the problem size, but there exist faster algorithms with linear complexity. Finally, in order to make a choice among the large and fuzzy set of available techniques, comparisons based on computer simulations in a relevant signal processing context are made View full abstract»

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