Glossary

Crosstalk. Electronic designers are quite aware of the phenomenon of crosstalk in interconnects : a signal intentionally injected on a conductor of the interconnect gives rise to an unwanted crosstalk signal, which may degrade the performances of a given system, or make it inoperative. The increase of speed and of bandwidth on the one hand, and of circuit and interconnect density on the other hand worsen this phenomenon, so that crosstalk is sometimes the limiting factor for the use of the most advanced technologies. Since the old telegraph days, engineers have fought crosstalk, because it takes place in various types of interconnects such as telecommunication cables, local area networks, printed circuit boards, on-chip interconnects, etc..
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DSP. DSP stands for "digital signal processing". The signals are processed in order to extract or to modify the information contained in them, or to adapt them to the means of transmission or to the means of information storage. The digital signal processing consists of processing a signal made of a set of discrete numbers (digital signal). Digital processing of an analog signal consists basically of three steps: conversion of the analog signal into a digital form, processing of the digital version, and finally conversion of the processed digital signal back into an analog form. DSP also stands for "digital signal processor". It is a microprocessor which architecture is optimized for the digital signal processing.
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Electromagnetic compatibility. See EMC.

EMC. EMC stands for "electromagnetic compatibility". The electromagnetic compatibility is the ability of a device, equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment. By extension, EMC also designate the scientific field of studying and understanding the EMC of items, and the technical field concerned with obtaining the EMC. Equipments and systems are often subject to mandatory EMC requirements. In Europe, most legal requirements are related to the application of the 89/336/EEC directive, also called EMC directive. The technical requirements are expressed in basic EMC standards from the Cenelec, and in product standards. Excem has a lot of activity in engineering for EMC, special measurements for EMC, problem solving for meeting EMC specifications, in providing instruments for electromagnetic measurements, and in editing software for EMC predictions. Excem has also an extensive experience in the EMC of installations, the protection against lightning and electromagnetic pulses, and the manufacturing and installation of special suppressors or filters.
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Electromagnetic pulse. See EMP.

SARL. The french "SARL" or "société à responsabilité limitée" is similar to the english "private company". The shares are called "parts sociales". The right to transfer the parts sociales is restricted. The head of a SARL is a "Gérant".
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Société par actions simplifiée. The french "société par actions simplifiée" is more or less equivalent to the "limited company" of english law. A société par actions simplifiée has its annual statements controlled by an independant body, and the annual summary and balance sheet are published. The head of a société par actions simplifiée is its "Président" (Chairman). However, this company, unlike the "société anonyme", does not have a board. The Président is also responsible for the operation of the company. The company may also have a "Directeur Général" (General manager), who has the same authority as the Président with respect to third parties.
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Submarine cables. Telecommunication submarine cables carry most of todays telecommunication traffic across oceans.
Coaxial submarine cables are no more installed, and most of them have been removed or abandonned, except where the traffic is light. Optical submarine cable systems with regenerators are also considered as implementing an old technology, though many such cables are still in operation. The current technology is optically amplified subsea cable systems, with wavelength domain multiplexing (WDM).
In practice all submarine cables for telecommunication have a metallic part insulated from the sea water. In cable systems with repeaters (optical amplifiers or regenerators), this conductor is used as a power-feed conductor. The ability of accurately and quickly locating faults on subsea cables is an important aspect of cable maintenance, because the unavailability of a cable system is very expensive.

Cable repair operations on a cable ship (Courtesy of France Telecom)

The above picture shows a cable being cut on a cable ship during maintenance operations. Excem is a manufacturer of fault location systems called the L2G. The L2G is used to locate the fault from a cable station, or from a cable ship. The L2G performs DC fault location, one of the most relevant fault location technique for fiber optic cables.
End of the article on "Submarine cables"

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