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  • Ahmed, Jawwad, et al. (författare)
  • A Dynamic Bulk Provisioning Framework for Concurrent Optimization in PCE-Based WDM Networks
  • 2012
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 30:14, s. 2229-2239
  • Tidskriftsartikel (refereegranskat)abstract
    • A centralized network control and management plane, such as the one based on a path computation element (PCE), is highly beneficial in terms of resource optimization in wavelength division multiplexing optical networks. Benefits of centralized provisioning are even more evident when connection requests are provisioned in batches, i.e., they allow a better use of network resources via concurrent optimization. In this study, a dynamic bulk provisioning framework is presented with the objective of optimizing the use of network resources that also presents, as an additional benefit, the ability to yield a reduction of the control plane overhead. The rationale behind the proposed framework is based on a mechanism in which the PCE client is allowed to bundle and simultaneously send multiple labeled switch path (LSP) requests to the PCE where, in turn, several bundles can be concurrently processed together as a single bulk. From the network deployment perspective, a PCE-based network architecture is proposed to practically realize this approach. For dynamic bulk provisioning of optical LSP requests, a time-efficient integer linear programming (ILP) model (LSP BP ILP) is presented to minimize the request blocking, the network resource consumption, and the network congestion. In addition, a heuristic based on a greedy randomized adaptive search procedure (GRASP), namely LSP_BP_GRASP, is also proposed as a scalable alternative. The presented results demonstrate significant advantages of the proposed PCE bulk provisioning framework based on concurrent optimization in terms of reduced blocking probability and control overhead when compared with conventional dynamic connection provisioning approaches processing a single connection request at a time.
  • Alic, N., et al. (författare)
  • Joint Statistics and MLSD in Filtered Incoherent High-Speed Fiber-Optic Communications
  • 2010
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 28:10, s. 1564-1572
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, signal statistics and their utilization for detection in narrowly filtered equalized high-speed fiber-optic communications are investigated experimentally. Tradeoffs between log-likelihood metric applications and oversampling are covered in detail. It is, for the first time, demonstrated that performance loss in bandwidth-limited systems can be nearly fully recovered (to within 0.5 dB) by taking advantage of band-width-limitation-induced noise correlations and oversampling.
  • Alvarado, Alex, 1982-, et al. (författare)
  • Four-Dimensional Coded Modulation with Bit-Wise Decoders for Future Optical Communications
  • 2015
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 33:10, s. 1993-2003
  • Tidskriftsartikel (refereegranskat)abstract
    • Coded modulation (CM) is the combination of forward error correction (FEC) and multilevel constellations. Coherent optical communication systems result in a four-dimensional (4D) signal space, which naturally leads to 4D-CM transceivers. A practically attractive design paradigm is to use a bit-wise decoder, where the detection process is (suboptimally) separated into two steps: soft-decision demapping followed by binary decoding. In this paper, bit-wise decoders are studied from an information-theoretic viewpoint. 4D constellations with up to 4096 constellation points are considered. Metrics to predict the post-FEC bit-error rate (BER) of bit-wise decoders are analyzed. The mutual information is shown to fail at predicting the post-FEC BER of bit-wise decoders and the so-called generalized mutual information is shown to be a much more robust metric. For the suboptimal scheme under consideration, it is also shown that constellations that transmit and receive information in each polarization and quadrature independently (e.g., PM-QPSK, PM-16QAM, and PM-64QAM) outperform the best 4D constellations designed for uncoded transmission. Theoretical gains are as high as 4 dB, which are then validated via numerical simulations of low-density parity check codes.
  • Bakke, T., et al. (författare)
  • Polymeric optical spot-size transformer with vertical and lateral tapers
  • 2002
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 20:7, s. 1188-1197
  • Tidskriftsartikel (refereegranskat)abstract
    • The design, fabrication, and characterization of a polymeric optical spot-size transformer with vertical and lateral tapers is reported. The vertical taper is formed by utilizing the planarization properties of a polymer, while the lateral taper is defined by photolithography. An optimization method for the taper shape is described based on fundamental results from coupled local mode theory. A total fiber to waveguide insertion loss of 0.6 dB has been measured with the integration of the transformer, an improvement of 2.1 dB. The spatial alignment tolerance for 1 dB excess loss was measured to ±2.7 µm, consistent with theory.
  • Bamiedakis, N., et al. (författare)
  • 40 Gb/s Data Transmission Over a 1-m-Long Multimode Polymer Spiral Waveguide for Board-Level Optical Interconnects
  • 2015
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 33:4, s. 882-888
  • Tidskriftsartikel (refereegranskat)abstract
    • Optical interconnects have attracted considerable attention for use in short-reach communication links within high-performance electronic systems, such as data centers, supercomputers, and data storage systems. Multimode polymer waveguides, in particular, constitute an attractive technology for use in board-level interconnects as they can be cost-effectively integrated onto standard PCBs and allow system assembly with relaxed alignment tolerances. However, their highly multimoded nature raises important concerns about their bandwidth limitations and their potential to support very high on-board data rates. In this paper, we report record error-free (BER < 10(-12)) 40 Gb/s data transmission over a 1-m-long multimode polymer spiral waveguide and present thorough studies on the waveguide bandwidth performance. The frequency response of the waveguide is investigated under a wide range of launch conditions and in the presence of input spatial offsets, which are expected to be highly-likely in real-world systems. A robust bandwidth performance is observed with a bandwidth-length product of at least 35 GHzxm for all launch conditions studied. The reported results clearly demonstrate the potential of this technology for use in board-level interconnects, and indicate that data rates of at least 40 Gb/s are feasible over waveguide lengths of 1 m.
  • Beygi, Lotfollah, 1977-, et al. (författare)
  • Rate-Adaptive Coded Modulation for Fiber-Optic Communications
  • 2014
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 32:2, s. 333-343
  • Tidskriftsartikel (refereegranskat)abstract
    • Rate-adaptive optical transceivers can play an important role in exploiting the available resources in dynamic optical networks, in which different links yield different signal qualities. We study rate-adaptive joint coding and modulation, often called coded modulation (CM), addressing non-dispersion-managed (non-DM) links, exploiting recent advances in channel modeling of these links. We introduce a four-dimensional CM scheme, which shows a better tradeoff between digital signal processing complexity and transparent reach than existing methods. We construct a rate-adaptive CM scheme combining a single low-density parity-check code with a family of three signal constellations and using probabilistic signal shaping. We evaluate the performance of the proposed CM scheme for single-channel transmission through long-haul non-DM fiber-optic systems with electronic chromatic-dispersion compensation. The numerical results demonstrate improvement of spectral efficiency over a wide range of transparent reaches, an improvement over 1 dB compared to existing methods.
  • Beygi, Lotfollah, 1977-, et al. (författare)
  • Signal Statistics in Fiber-Optical Channels with Polarization Multiplexing and Self-Phase Modulation
  • 2011
  • Ingår i: IEEE Journal of Lightwave Technology. - 0733-8724. ; 29:16, s. 2379-2386
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, the statistics of received signals in a single-channel dispersion-managed dual-polarization fiber-optical channel are derived in the limit of low dispersion. The joint probability density function (pdf) of the received amplitudes and phases of such a system is derived for both lumped and distributed amplification. The new pdf expressions are used to numerically evaluate the performance of modulation formats over channels with nonlinear phase noise. For example, a sensitivity gain of up to 2 dB is calculated for a specific system using polarization-multiplexed 8-ary phase shift keying compared with a similar single-polarization system at the same spectral efficiency and a symbol error rate of 5*10^(-4). Moreover, the accuracy of the derived pdf is evaluated for some single-channel dispersion-managed fiber-optical links with different dispersion-maps using the split-step Fourier transform method.
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