{"id":1487,"date":"2018-04-05T15:44:00","date_gmt":"2018-04-05T19:44:00","guid":{"rendered":"https:\/\/www.precisionot.com\/?p=1487"},"modified":"2021-01-15T12:56:08","modified_gmt":"2021-01-15T17:56:08","slug":"technologie-cdr-ses-effets-perte-dintegrite","status":"publish","type":"post","link":"https:\/\/www.precisionot.com\/fr\/cdr-technology-its-effects-integrity-loss\/","title":{"rendered":"La technologie CDR et ses effets sur la perte d&#039;int\u00e9grit\u00e9"},"content":{"rendered":"<p class=\"wp-block-paragraph\">Le transfert de donn\u00e9es d&#039;un point \u00e0 un autre comporte intrins\u00e8quement un risque de perte d&#039;int\u00e9grit\u00e9\u00a0; c&#039;est la nature de la b\u00eate. En particulier dans le domaine des communications \u00e0 haut d\u00e9bit, de nombreux facteurs (bruit du signal, pics statiques, etc.) peuvent pr\u00e9senter des obstacles \u00e0 la transmission des donn\u00e9es.\u00a0<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">L&#039;un des d\u00e9fis les plus courants consiste \u00e0 mettre l&#039;\u00e9metteur et le r\u00e9cepteur sur la m\u00eame longueur d&#039;onde en termes de synchronisation du signal, ce qui peut \u00eatre plus complexe qu&#039;il n&#039;y para\u00eet. <\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"alignright size-large is-resized\"><img decoding=\"async\" src=\"https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-09-28-am.png\" alt=\"comparaison de trois flux de donn\u00e9es diff\u00e9rents\" class=\"wp-image-3334\" width=\"259\" height=\"193\" srcset=\"https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-09-28-am.png 533w, https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-09-28-am-300x223.png 300w, https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-09-28-am-16x12.png 16w\" sizes=\"(max-width: 259px) 100vw, 259px\" \/><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">Pour mieux expliquer la difficult\u00e9, consid\u00e9rons les 19<sup>e<\/sup>technologie de communication du si\u00e8cle du code Morse. Bas\u00e9 sur une s\u00e9rie d&#039;impulsions \u00e9lectriques marche\/arr\u00eat, le syst\u00e8me de repr\u00e9sentation des caract\u00e8res de texte par de longs tirets et des points courts n&#039;est pas sans rappeler un syst\u00e8me binaire qui utilise des uns et des z\u00e9ros. Le code Morse a \u00e9t\u00e9 con\u00e7u de sorte que la longueur de chaque caract\u00e8re soit l&#039;inverse approximatif de la fr\u00e9quence \u00e0 laquelle il appara\u00eet dans la langue anglaise - la lettre la plus courante, E, est repr\u00e9sent\u00e9e par un seul point; deux points repr\u00e9sentent la lettre I ; trois points repr\u00e9sentent la lettre S ; et ainsi de suite.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Tant que l&#039;\u00e9metteur et le r\u00e9cepteur poss\u00e8dent une compr\u00e9hension commune de la synchronisation du signal, le code peut \u00eatre correctement interpr\u00e9t\u00e9. Mais supposons que le code devait \u00eatre transmis \u00e0 un rythme diff\u00e9rent de celui que le r\u00e9cepteur interpr\u00e8te : ce qui \u00e9tait cens\u00e9 \u00eatre deux Es pourrait plut\u00f4t \u00eatre mal interpr\u00e9t\u00e9 comme un seul I, ou ce qui est signifi\u00e9 comme un S pourrait \u00eatre mal interpr\u00e9t\u00e9 comme trois Es.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"alignleft size-large is-resized\"><img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-17-52-am.png\" alt=\"Morse\" class=\"wp-image-3335\" width=\"201\" height=\"303\" srcset=\"https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-17-52-am.png 328w, https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-17-52-am-199x300.png 199w, https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-17-52-am-8x12.png 8w, https:\/\/www.precisionot.com\/wp-content\/uploads\/screen-shot-2018-04-05-at-8-17-52-am-300x453.png 300w\" sizes=\"(max-width: 201px) 100vw, 201px\" \/><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">L&#039;une des fa\u00e7ons dont les interfaces de communication modernes peuvent r\u00e9soudre ce probl\u00e8me consiste \u00e0 inclure un flux de donn\u00e9es suppl\u00e9mentaire \u00e0 l&#039;extr\u00e9mit\u00e9 \u00e9mettrice pour servir d&#039;&quot;horloge&quot;. L&#039;horloge est un signal marche\/arr\u00eat alternatif \u00e0 cadencement r\u00e9gulier qui sert de r\u00e9f\u00e9rence pour la fr\u00e9quence des donn\u00e9es transmises. Il ordonne efficacement au r\u00e9cepteur d&#039;interpr\u00e9ter le signal \u00e0 un rythme sp\u00e9cifique.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Le seul probl\u00e8me est que de nombreux flux de donn\u00e9es \u00e0 grande vitesse sont envoy\u00e9s sans signal d&#039;horloge d&#039;accompagnement, ce qui leur permet d&#039;\u00eatre plus rapides, d&#039;utiliser moins d&#039;\u00e9nergie, d&#039;\u00eatre soumis \u00e0 moins d&#039;interf\u00e9rences, etc. Afin d&#039;interpr\u00e9ter de mani\u00e8re fiable les donn\u00e9es transmises, le r\u00e9cepteur doit donc r\u00e9g\u00e9n\u00e9rer l&#039;horloge. Pour ce faire, une fr\u00e9quence approximative est utilis\u00e9e pour g\u00e9n\u00e9rer une horloge de r\u00e9f\u00e9rence, qui peut ensuite \u00eatre align\u00e9e en phase sur les transitions dans le flux de donn\u00e9es entrant. L&#039;horloge est alors dite &quot;r\u00e9cup\u00e9r\u00e9e&quot;. Et une fois l&#039;horloge r\u00e9cup\u00e9r\u00e9e, les donn\u00e9es peuvent \u00e9galement \u00eatre r\u00e9cup\u00e9r\u00e9es, g\u00e9n\u00e9rant un flux binaire en \u00e9chantillonnant l&#039;horloge avec les donn\u00e9es entrantes. &nbsp;<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Cette combinaison de r\u00e9cup\u00e9ration d&#039;horloge et de donn\u00e9es est connue sous le nom de CDR et constitue un \u00e9l\u00e9ment cl\u00e9 des syst\u00e8mes de communication optique.&nbsp; &nbsp;<\/p>","protected":false},"excerpt":{"rendered":"<p>Le transfert de donn\u00e9es d&#039;un point \u00e0 un autre comporte intrins\u00e8quement un risque de perte d&#039;int\u00e9grit\u00e9\u00a0; c&#039;est la nature de la b\u00eate.<\/p>","protected":false},"author":33,"featured_media":1488,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"content-type":"","site-sidebar-layout":"default","site-content-layout":"default","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center 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