Connections and Connectionless Data Transmission

Article Abstract:

The Reference Model for Open Systems Interconnection (OSI) uses both connection-mode data transfer and connectionless data transmission as fundamental models. A connection is a dynamic association between two or more entities to control the transfer of data between them. Connection-mode transfer displays a clearly distinguishable lifetime, three-party agreement, negotiation and renegotiation connection identifiers, and a data unit relationship. A model for connection-mode can be constructed from a queue. Connectionless data transmission is transmission of independent data from a source service access point to destination access points in the absense of a connection. Connectionless transmission is characterized by a two-party agreement, single-access service, no negotiation, data unit independence, and self-contained data units. Connection and connectionless models are discussed in relation to the standards for each of the seven layers of OSI architecture. Diagrams illustrate relevant concepts.

Standard, Standardization, Local area networks, LAN, Communications protocols, Protocol, Networks, CCITT, OSI Standard, ISO

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Information transmission with photon-number-squeezed light

Article Abstract:

There are several proposed methods for generating photon-number-squeezed (sub-Poisson) light by imparting an anticorrelation that regularizes the times of the arrival of the photons to the photon stream. There are two means of accomplishing this: by controlling the excitation or emission process; or through feedback by using a copy of the photon point processes when emissions occur in pairs. The channel capacity for receivers in which the photon arrival times are observed cannot be improved by modifying a Poisson photon stream into a sub-Poisson stream. Improvement in channel capacity is possible for photon-counting receivers. Bit-error rates in on-off keying communications systems using sub-Poisson photons created by introducing anticorrelation into a Poisson beam can be smaller than the error rates of the Poisson channel.

Pressed and blown glass, not elsewhere classified, Product introduction, Photonics, Information theory, Technical, Poisson distribution, New Technique

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Nonlinear effects in coherent multichannel transmission through optical fibers

Article Abstract:

Strong nonlinear reactions in optical materials set an upper limit on the power levels that may be transmitted without adverse effects on the operation of optical transmission systems. The major nonlinear reactions affecting single mode optical fibers are four wave mixing (FWM), stimulated Brillouin scattering (SBS), and stimulated Raman scattering (SRS). The limitations these interactions place on transmission power levels ultimately limits the length of long-haul transmission systems. An even greater importance in systems design may accrue to these nonlinearities in the future as power levels available from semiconductor lasers continue to increase, use of optical amplifiers becomes uniform, and use of ultra low loss fibers increases.

Industrial research, Telecommunications, Research and Development, Communications Technology, Transmission Lines, technical, Optical Communication

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