To extend a fiber-optic transmission system from traditional C band to C+L band, it is necessary to place Raman amplifiers to improve the optical signal-to-noise ratios (OSNR) of lightpaths. We develop a heuristic algorithm for optimal Raman amplifier placement. Simulations show that the proposed algorithm is efficient to require up to 50% fewer Raman amplifiers compared with benchmark schemes.
To meet the ever-increasing demand for data traffic, the simplified coherent optical communications, which exhibit the advantages of low cost, low power consumption and high capacity, have garnered the widespread attention for short-reach optical communications applications. To further reduce the cost of coherent optical transmissions, we for the first time propose and demonstrate the capability of non-integer-oversampling clock data recovery (CDR) to process the noise-shaped signals which is robust to the quantization noise when using cheap digital-to-analog converters (DACs). The 192-Gbps dual-polarization quadrature amplitude modulation- 16 (DP-QAM-16) transmissions are experimentally realized by jointly implementing the noise shaping (NS) technique and 4/3 samples per symbol (sps) CDR processing. Experimental results indicate that 1.2- and 1-dB Q factor gains have been achieved by using the proposed simplified coherent optical transmission structure, under the constraints of 3- and 4-bit quantization respectively. We believe that the joint implementation of NS and non-integer-oversampling CDR is promising for simplifying the coherent optical transmissions for low-cost optical communications applications.
Hyperspectral images with an immense number of spectral bands provide abundant discriminant information for accurate land-cover classification in the remote sensing field. However, these narrow and adjacent bands contain a large amount of redundant information. Analyzing these images always requires a huge storage space with expensive computational costs. Furthermore, their high correlation coefficient would lead to the Hughes phenomenon, hindering the improvement of classification performance. We propose a linear semi-supervised hyperspectral feature extraction method L3ME to learn latent local manifold embeddings. Although labeled samples are beneficial to construct learning models, their number is always limited in real-world tasks. The motivation of this paper is to jointly enhance the contributions of labeled and unlabeled samples for learning local manifold structures of hyperspectral images. Features in labeled samples are extracted by two procedures, the adaptive patch alignment framework and integrated intraclass-interclass relationships, from different perspectives. The former aims to solve the problem of the uneven distribution of classes by introducing spectral angle based adaptive parameters. The latter aims to solve the problem of the uneven distribution of samples by constructing several adjacency graphs. The locality preserving projection is capable of preserving the local neighborhood structure of samples. A penalty for sparse regularization is cleverly integrated into the proposed linear discriminant objective function, which is optimized using a novel updating strategy. The convergence of L3ME is proved in detail and analyzed in this paper. Experiments on three typical hyperspectral datasets illustrate the effectiveness of the proposed method over some state-of-the-art techniques. The implementation of L3ME is available at https://github.com/biowby/L3ME.
Dispersion compensation with a wavelength selective switch-based reconfigurable optical add/drop multiplexer is experimentally realized in an optical transport network testbed. Through considering various dispersion compensation scenarios (including different fiber types, different wavelength ranges, and single- and multi-channel cases), we show that without deploying new optical components, a wavelength selective switch can successfully compensate for chromatic dispersion in its dispersion control range.
In the wavelength-routed optical transport networks, fixed shortest path routing is one of major lightpath service
provisioning strategies, which shows simplicity in network control and operation. Specifically, once a shortest route is
found for a node pair, the route is always used for any future lightpath service provisioning, which therefore does not
require network control and management system to maintain any active network-wide link state database. On the other
hand, the fixed shortest path routing strategy suffers from the disadvantage of unbalanced network traffic load
distribution and network congestion because it keeps on employing the same fixed shortest route between each pair of
nodes. To avoid the network congestion and meanwhile retain the operational simplicity, in this study we develop a
Load-Balanced Fixed Routing (LBFR) algorithm. Through a training process based on a forecasted network traffic load
matrix, the proposed algorithm finds a fixed (or few) route(s) for each node pair and employs the fixed route(s) for
lightpath service provisioning. Different from the fixed shortest path routes between node pairs, these routes can well
balance traffic load within the network when they are used for lightpath service provisioning. Compared to the
traditional fixed shortest path routing algorithm, the LBFR algorithm can achieve much better lightpath blocking
performance according to our simulation and analytical studies. Moreover, the performance improvement is more
significant with the increase of network nodal degree.
Many of the features of EPON and WiMAX are complementary. In [1] we proposed four basic architectures for the
integration of EPON and WiMAX, which employs an EPON as a backhaul to interconnect multiple WiMAX base
stations. The integration takes advantage of the high capacity of fibre communication as well as the mobile and non-line
of sight (NLOS) features of wireless communication. In this article, we recap these basic architectures and relevant
operational issues. We further propose more integrated architectures that are extended from the four basic architectures.
In addition, more design and operational issues relevant to the architectures are discussed. We expect that integration of
EPON and WiMAX can help realize fixed mobile convergence, and significantly reduce overall design and operational
costs for the new-generation broadband access networks.
As an alternative of the Shared Backup Path Protection (SBPP) method, we develop a framework for dynamic provisioning of survivable services based on the use of p-cycles to form a Protected Working Capacity Envelope (PWCE) within which dynamic provisioning of protected services is greatly simplified. Based on p-cycles, the restoration speed of rings is obtained, but with the capacity efficiency of shared-mesh networks. In addition, with PWCE, arbitrarily fast dynamic service demands can be handled with much less complexity (in terms of database dependency and state update dissemination) than under SBPP. Only a simple OSPF-topology view of non-exhausted spans in the envelope is required. If a new path can be routed through the envelope, it is protected by virtue of being routable. This is in contrast to needing a full database of network state so that the end-user can set up a shared backup protection path under SBPP. In addition, dissemination of state updates occurs only on the time-scale of the non-stationary evolution of the demand statistics, not on the time-scale of individual connections. During statistically stationary periods, there is no dissemination of state updates whatsoever with an envelope that is well matched to its load. The PWCE concept thus offers some new tradeoffs between operational simplicity and spare capacity efficiency. The main contribution of this work is the detailed implementation and simulation of test networks operating under PWCE and designed with novel envelope volume maximizing formulations.
We study the forcer concept in the context of p-cycle based networks. A simple but efficient forcer analysis method is proposed specifically for span-restorable networks in general. Besides identifying forcers, the method is also capable of exploiting extra servable working channels given an initial network spare capacity budget designed for pre-existing working capacities. We find that a large number of extra working channels can be served with no increase in the pre-planned spare capacity budget. This attribute of p-cycle protected networks can be used to enhance their ability to serve unforeseen demand patterns or provide an expanded envelope of protected working capacity within which dynamic demand is servable without blocking due to exceeding the protected working capacity limits.
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