Irina Vasile

Optical solutions for unbundled access network

The unbundling technique requires finding solutions to guarantee the economic and technical performances imposed by the nature of the services that can be offered. One of the possible solutions is the optic one; choosing this solution is justified for the following reasons: it optimizes the use of the access network, which is the most expensive part of a network (about 50% of the total investment in telecommunications networks) while also being the least used (telephone traffic on the lines has a low cost); it increases the distance between the master station/central and the terminal of the subscriber; the development of the services offered to the subscribers is conditioned by the subscriber network. For broadband services there is a need for support for the introduction of high-speed transport. A proper identification of the factors that must be satisfied and a comprehensive financial evaluation of all resources involved, both the resources that are in the process of being bought as well as extensions are the main conditions that would lead to a correct choice. As there is no single optimal technology for all development scenarios, which can take into account all access systems, a successful implementation is always done by individual/particularized scenarios. The method used today for the selection of an optimal solution is based on statistics and analysis of the various, already implemented, solutions, and on the experience that was already gained; the main evaluation criterion and the most unbiased one is the ratio between the cost of the investment and the quality of service, while serving an as large as possible number of customers.The unbundling technique requires finding solutions to guarantee the economic and technical performances imposed by the nature of the services that can be offered. One of the possible solutions is the optic one; choosing this solution is justified for the following reasons: it optimizes the use of the access network, which is the most expensive part of a network (about 50% of the total investment in telecommunications networks) while also being the least used (telephone traffic on the lines has a low cost); it increases the distance between the master station/central and the terminal of the subscriber; the development of the services offered to the subscribers is conditioned by the subscriber network. For broadband services there is a need for support for the introduction of high-speed transport.

Optical transmission techniques

An optical transmission system is a method of transferring information in the shape of bits or symbols for the case of digital systems, and of analogue waves for the case of analogue systems, between fixed points located on a fiber optics cable. Today and in the near future there are numerous such transmission techniques available. The increase of demands for data transfer from phone subscribers can be met only by means of digital techniques applied in the local network, in addition to the use of digital telephone exchange and of the digital transmission systems in the trees network. In order to increase the quantity of information transferred through one fiber, optical multiplexing techniques have been conceived and tested. The optical multiplexing is additional to the electrical signal multiplexing. The requests for the access network will become more and more complex, a larger flexibility and a wider band being needed. For the purpose of complying with these requests, the coherent simultaneous or alternative transmission towards the optical amplifiers represents a factor of technical progress. The multiplexing with wave length division allows for more channels to be transported through the same fiber with different wave lengths, in one or both directions.

Optic fiber access network through SDH systems

The communication networks, highly specialized, were developed according to the type of transmitted information (vocal signal, data bases, TV signals). Presently, the networks’ evolution is targeted towards high velocities and services integration, networks characterized by SONET/SDH standards. SDH (Synchronous Digital Hierarchy) is the first standard, which provides an integrated system of network management and maintenance, ensures a uniform and global hierarchy of multiplexing and has advantages concerning the configuration of external network types. In this paper is described an access network for voice and dates communications, on optic fiber, built up with LOGES 2M Alcatel access routes (2 Mbps access) and with SDH transmission systems type Alcatel 1641SM (155Mbps).

Automatic segmentation of infantile hemangiomas within an optimally chosen color space

Infantile hemangiomas (IH) are benign vascular tumors, most of them appearing in the first weeks and developing until six months of age. The evaluation of the lesion size is usually made by the physician through manual measurement, which is inaccurate. This paper presents an algorithm for the automatic segmentation of the hemangioma region, relying on the Maximum a Posteriori (MAP) classification method. The segmentation result is improved by regularization with discrete Markov fields (MAP-Markov). Then, a further improvement is performed, by eliminated distant non-hemangioma pixels. The optimal color space is chosen before segmentation, from five different color spaces, by iteratively computing the segmentation error 10 times on each color space and each of the 40 images from the database. The segmentation performance is evaluated in terms of border error.

Modern techniques and technologies for unbundled access in the local loop

The efficient and unbundled use of the existing telecommunications infrastructure represents a major goal for the development of the services offered by telecommunications providers. A major telecommunications operator can provide services to a subscriber using a copper wire pair or part of the frequency spectrum of a copper wire pair, together with other operators, through a process of unbundling access in the local loop. Since access to the vocal band is an already solved problem, concerns turn to the broadband access with xDSL service delivery on ungrouped subscriber loops; besides the legal and economic aspects involved this has become an engineering problem also. The local loop unbundling methods have a substantial technical impact. This impact should be taken into account right from the design stage and then in the standardization stage of broadband systems intended to operate on copper wire pairs in the local loop. These systems are known under the generic term of xDSL and began to be analyzed in the late 90s. xDSL became the dominant solution for providing Internet at a reasonable price for both residential and business subscribers. In this massive development scenario, certain problems will arise from the early stages of deployment, and another type of problems will occur later on when a large number of systems will be installed in a single beam.

Hand posture recognition using the intrinsic dimension

This paper presents a hand posture recognition algorithm based on the intrinsic dimension (ID). Hand segmentation is reliable with cluttered background due to the use of the time-of-flight (ToF) range camera. The hand pose recognition is performed using an image indexing technique with a reference database of 360 images. The database and the query images consist of nine types of hand postures. The similarity measure used for finding the best match with the query image is the correlation between the 1D representations of the 2D ID hand contours. The average recognition rate is above 96%, which is satisfactory.

Coupling devices for smart transducers with optical fiber link used in automotive industry

The fiber optic transmission systems have been used extensively for obtaining communication and intercommunication links within the public telephonic network, but lately the fiber optics has entered the vehicles field. The cable method might imply low costs if the coupling of the transducers to the optical fiber is optimised from the point of view of cost and fiability. The paper presents several methods of the optical fiber coupling, implying a glass or a plastic optical fiber, based on modern optical devices produced by Infineon.

Wavelength division multiplexing WDM, CWDM and DWDM applications

The fiber optics has become the most preferred media for this very large data traffic. TDM (Time Division Multiplexing) has been the most practical method to divide the significant capacity of a single fiber optics into several communication channels. This technology is still limited by the large complexity of high-flow modulation and multiplexing equipment. Presently, a complementary approach proves its potential: Wavelength-Division Multiplexing (WDM). The evolution of WDM allows now a very small spacing between channels wavelength, in nm, generating DWDM (Dense Wavelength Division Multiplexing). The networks with individual fibers including more than 100 independent optic channels, as well as those with bidirectional flow are already available on the market. CWDM (Coarse Wavelength Division Multiplexing) represents an economical application of a mature technology which may provide options where the capacity of fibers is limited.

Architectures of fiber optic network in telecommunications

The operators of telecommunications have targeted their efforts towards realizing applications using broad band fiber optics systems in the access network. Thus, a new concept related to the implementation of fiber optic transmission systems, named FITL (Fiber In The Loop) has appeared. The fiber optic transmission systems have been extensively used for realizing the transport and intercommunication of the public telecommunication network, as well as for assuring the access to the telecommunication systems of the great corporations. Still, the segment of the residential users and small corporations did not benefit on large scale of this technology implementation. For the purpose of defining fiber optic applications, more types of architectures were conceived, like: bus, ring, star, tree. In the case of tree-like networks passive splitters (thats where the name of PON comes from -Passive Optical Network-), which reduce significantly the costs of the fiber optic access, by separating the costs of the optical electronic components. Thats why the passive fiber optics architectures (PON represent a viable solution for realizing the access at the users loop. The main types of fiber optics architectures included in this work are: FTTC (Fiber To The Curb); FTTB (Fiber To The Building); FTTH (Fiber To The Home).