{"id":3793,"date":"2026-05-12T08:54:50","date_gmt":"2026-05-12T08:54:50","guid":{"rendered":"https:\/\/lp.szlogic.cn\/glossary\/xlaui-10-lane-attachment-unit-interface-ethernet-explained\/"},"modified":"2026-05-26T06:17:06","modified_gmt":"2026-05-26T06:17:06","slug":"xlaui-10-lane-attachment-unit-interface-ethernet-explained","status":"publish","type":"post","link":"https:\/\/lp.szlogic.cn\/ru\/glossary\/xlaui-10-lane-attachment-unit-interface-ethernet-explained","title":{"rendered":"What Is XLAUI? 10-Lane Attachment Unit Interface Explained"},"content":{"rendered":"<figure class=\"wp-block-image aligncenter size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1200\" height=\"712\" src=\"https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/01c637791b5742329bd6f1ee40a189b2.webp\" alt=\"What Is XLAUI? 10-Lane Attachment Unit Interface Explained\" class=\"wp-image-3790\" srcset=\"https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/01c637791b5742329bd6f1ee40a189b2.webp 1200w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/01c637791b5742329bd6f1ee40a189b2-300x178.webp 300w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/01c637791b5742329bd6f1ee40a189b2-1024x608.webp 1024w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/01c637791b5742329bd6f1ee40a189b2-768x456.webp 768w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/01c637791b5742329bd6f1ee40a189b2-18x12.webp 18w\" sizes=\"(max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" >&#x1f4d8; Introduction<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">High-speed networking requires robust and standardized electrical interfaces to ensure reliable 40 Gb\/s links between host ASICs and pluggable optical modules. One critical interface in this domain is the <strong>10-lane Attachment Unit Interface (XLAUI)<\/strong>, defined in the IEEE 802.3ba standard. Engineers, system architects, and module integrators deploying 40G QSFP+ modules benefit from a clear understanding of XLAUI to ensure interoperability, signal integrity, and predictable performance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This article explains what XLAUI is, how it operates, why it matters in 40G QSFP+ modules, and provides practical insights using <a target=\"_blank\" rel=\"\" href=\"https:\/\/www.l-p.com\/store-26153-40g-qsfp.htm\"><strong>LINK-PP 40G QSFP+ modules<\/strong><\/a> as real-world examples.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" >&#x1f4d8; What is XLAUI?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>XLAUI<\/strong> stands for <strong>eXtended 10-Lane Attachment Unit Interface<\/strong>. It is an electrical interface defined in <a target=\"_blank\" rel=\"\" href=\"https:\/\/resources.l-p.com\/knowledge-center\/what-is-ieee-802-3ba-standard\">IEEE 802.3ba<\/a> for <strong>40 Gigabit Ethernet (40GbE)<\/strong>. XLAUI is used for <strong>chip-to-module<\/strong> or <strong>chip-to-chip<\/strong> connections, particularly in pluggable modules like QSFP+.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Key characteristics:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p><strong>Lane structure:<\/strong> 10 parallel lanes, each operating at ~10.3125 Gb\/s, aggregating to ~40 Gb\/s of user data after encoding.<\/p><\/li><li><p><strong>Applications:<\/strong> Host-to-module links for optical or copper backplanes.<\/p><\/li><li><p><strong>Electrical standards:<\/strong> Defined in Annex 83A of IEEE 802.3ba, including transmitter\/receiver parameters, channel loss budgets, return loss, and jitter budgets.<\/p><\/li><li><p><strong>Relationship to other AUIs:<\/strong> Part of the &#8220;Attachment Unit Interface&#8221; family\u2014like XAUI (10GbE) or CAUI (100GbE), but optimized for 40GbE.<\/p><\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">XLAUI allows for manageable lane speeds while achieving high aggregate bandwidth, making it practical for dense switch and server designs.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" >&#x1f4d8; How XLAUI Works<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" >\u25b7 Lane Structure &amp; Data Rate<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>Each of the 10 lanes carries ~10.3125 Gb\/s.<\/p><\/li><li><p>After 64b\/66b encoding, aggregate user data rate reaches ~40 Gb\/s.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >\u25b7 SERDES Operation<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>Each lane uses a <a target=\"_blank\" rel=\"\" href=\"https:\/\/resources.l-p.com\/glossary\/serdes-interfaces-high-speed-data-transfer-and-signal-integrity\"><strong>Serializer\/Deserializer (SERDES)<\/strong><\/a> to convert parallel data to serial streams and vice versa.<\/p><\/li><li><p>Modules or retimers may use a <strong>gearbox<\/strong> to map 10 electrical lanes into fewer optical lanes (e.g., 10\u21924 mapping).<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >\u25b7 Channel Requirements<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>IEEE 802.3ba specifies channel loss, return loss, <a target=\"_blank\" rel=\"\" href=\"https:\/\/resources.l-p.com\/knowledge-center\/jitter-in-optics-causes-effects-measurement-reduction\">jitter<\/a>, and skew limits.<\/p><\/li><li><p>Example: ~10 dB loss allowed at Nyquist frequency (~5.15625 GHz) for typical 250 mm FR4 PCB traces.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >\u25b7 Chip-to-Module vs Chip-to-Chip<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>XLAUI is primarily a <strong>chip-to-module<\/strong> interface (<a target=\"_blank\" rel=\"\" href=\"https:\/\/resources.l-p.com\/glossary\/what-is-application-specific-integrated-circuit-asic\">ASIC<\/a> \u2192 <a target=\"_blank\" rel=\"\" href=\"https:\/\/www.l-p.com\/products\/491483.htm\">QSFP+<\/a>).<\/p><\/li><li><p>Can also support backplane or PCB interconnects with proper signal integrity management.<\/p><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" >&#x1f4d8; Importance of XLAUI in 40G QSFP+ Modules<\/h2>\n\n\n\n<figure class=\"wp-block-image aligncenter size-large\"><img decoding=\"async\" width=\"1200\" height=\"712\" src=\"https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/cd32dba2684e4869a0a76d8a1ab143eb.webp\" alt=\"XLAUI in 40G QSFP+ Modules\" class=\"wp-image-3342\" srcset=\"https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/cd32dba2684e4869a0a76d8a1ab143eb.webp 1200w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/cd32dba2684e4869a0a76d8a1ab143eb-300x178.webp 300w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/cd32dba2684e4869a0a76d8a1ab143eb-1024x608.webp 1024w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/cd32dba2684e4869a0a76d8a1ab143eb-768x456.webp 768w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/cd32dba2684e4869a0a76d8a1ab143eb-18x12.webp 18w\" sizes=\"(max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\" >1. Higher Port Density<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>Multiple ~10 Gb\/s lanes are easier to route than a single ultra-high-speed lane.<\/p><\/li><li><p>Enables compact QSFP+ form factors and high-density linecards.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >2. Standardized Compatibility<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>Standardization allows module and ASIC vendors (e.g., LINK-PP) to design to a common interface.<\/p><\/li><li><p>Interoperability is improved across multi-vendor systems.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >3. Manageable Signal Integrity<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>Moderate lane speeds simplify PCB design, hot-plug connector implementation, and reduce retimer requirements.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >4. Future-Proofing<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>XLAUI remains relevant for legacy 40G modules and mixed-rate fabrics, even with emerging 25G\/50G lane technologies.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >LINK-PP 40G QSFP+ Modules and XLAUI<\/h3>\n\n\n\n<figure class=\"wp-block-image aligncenter size-large\"><img decoding=\"async\" width=\"1200\" height=\"712\" src=\"https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/3d5106edaa294519a6049787ffac25c9.webp\" alt=\"40G QSFP+ Modules\" class=\"wp-image-3791\" srcset=\"https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/3d5106edaa294519a6049787ffac25c9.webp 1200w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/3d5106edaa294519a6049787ffac25c9-300x178.webp 300w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/3d5106edaa294519a6049787ffac25c9-1024x608.webp 1024w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/3d5106edaa294519a6049787ffac25c9-768x456.webp 768w, https:\/\/lp.szlogic.cn\/wp-content\/uploads\/2026\/05\/3d5106edaa294519a6049787ffac25c9-18x12.webp 18w\" sizes=\"(max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Example:<\/strong> LINK\u2011PP <a target=\"_blank\" rel=\"\" href=\"https:\/\/www.l-p.com\/products\/491483.htm\">LQ\u2011CW40\u2011LR4C<\/a> 40G QSFP+ module<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>Converts 4\u00d710 Gb\/s electrical lanes into 4 CWDM optical signals.<\/p><\/li><li><p>Compatible with IEEE 802.3ba electrical interface standards, effectively implementing XLAUI-like 10-lane operation on the host side.<\/p><\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Design implications:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\" >\n<li><p>Host ASIC or switch must support a <strong>10-lane XLAUI interface<\/strong>.<\/p><\/li><li><p>PCB design must ensure signal integrity, lane alignment, and skew control.<\/p><\/li><li><p>Confirm vendor compatibility for electrical interface adherence.<\/p><\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\"><a target=\"_blank\" rel=\"\" href=\"https:\/\/www.l-p.com\/store-25432-optics-transceivers-sfp-modules.htm\">LINK-PP modules<\/a> adhere to IEEE standards, enabling predictable performance and simplified integration in 40G systems.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" >&#x1f4d8; Design Considerations &amp; Best Practices<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p><strong>Lane skew control:<\/strong> Ensure lane-to-lane skew is within specification for proper SERDES\/gearbox alignment.<\/p><\/li><li><p><strong>Jitter budget:<\/strong> Follow IEEE transmitter\/receiver jitter masks (Annex 83A).<\/p><\/li><li><p><strong>Channel loss budget:<\/strong> Typical ~10 dB loss at Nyquist frequency for ~250 mm FR4 traces.<\/p><\/li><li><p><strong>SERDES calibration:<\/strong> Implement pre-emphasis, CTLE, and DFE as required.<\/p><\/li><li><p><strong>Module compatibility:<\/strong> Verify host interface and QSFP+ form factor alignment.<\/p><\/li><li><p><strong>Future-proofing:<\/strong> Plan for 100G (CAUI-10) or 400G systems with lane breakout flexibility.<\/p><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" >&#x1f4d8; Summary<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>XLAUI <\/strong>(10-Lane Attachment Unit Interface) is a <strong>critical electrical interface standard<\/strong> for 40GbE systems. By splitting 40G into ten ~10.3 Gb\/s lanes, it enables modular, high-density, and interoperable QSFP+ deployments. Engineers integrating <a target=\"_blank\" rel=\"\" href=\"https:\/\/www.l-p.com\/store-26153-40g-qsfp.htm\"><strong>LINK-PP 40G QSFP+ transceivers<\/strong><\/a> must understand XLAUI to ensure proper PCB design, SERDES configuration, and reliable data-center performance.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" >&#x1f4d8; FAQ<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" >1. What is the primary purpose of XLAUI?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">XLAUI provides a standardized 10-lane electrical interface between a host ASIC (or PHY) and a 40G QSFP+ module. It enables reliable 40 Gb\/s data transfer while maintaining manageable lane speeds (~10.3125 Gb\/s) for signal integrity and PCB routing.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" >2. How does XLAUI differ from XAUI or CAUI?<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p><strong>XAUI:<\/strong> 4 lanes for 10GbE (~3.125 Gb\/s per lane after encoding).<\/p><\/li><li><p><strong>XLAUI:<\/strong> 10 lanes for 40GbE (~10.3125 Gb\/s per lane).<\/p><\/li><li><p><strong>CAUI:<\/strong> 10 or 20 lanes for 100GbE (~10\u201325 Gb\/s per lane).<br\/>XLAUI balances higher aggregate bandwidth with moderate per-lane speeds to simplify system design.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >3. Can XLAUI be used for backplane connections?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Yes. While primarily designed for chip-to-module links (ASIC \u2192 QSFP+), XLAUI can support backplane or PCB interconnects if channel loss, skew, and signal integrity requirements are met.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" >4. What is the role of SERDES and gearbox in XLAUI?<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p><a target=\"_blank\" rel=\"\" href=\"https:\/\/resources.l-p.com\/glossary\/serdes-interfaces-high-speed-data-transfer-and-signal-integrity\"><strong>SERDES<\/strong><\/a><strong>:<\/strong> Converts parallel data to serial streams (and vice versa) on each of the 10 lanes.<\/p><\/li><li><p><strong>Gearbox (optional):<\/strong> Maps multiple electrical lanes to fewer optical lanes inside the module (e.g., 10 electrical \u2192 4 optical lanes) while maintaining alignment.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >5. Are all 40G QSFP+ modules XLAUI-compliant?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Not all. Some modules use alternative 4-lane electrical interfaces like XLPPI or XLAUI-4. Always check the module datasheet for lane count, electrical interface type, and host compatibility.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" >6. How do I ensure proper lane alignment and signal integrity?<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>Control lane-to-lane skew within IEEE specifications.<\/p><\/li><li><p>Adhere to channel loss and jitter budgets.<\/p><\/li><li><p>Use SERDES features such as pre-emphasis, CTLE, and DFE as recommended.<\/p><\/li><li><p>Validate PCB routing, connector, and retimer performance.<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >7. Why is XLAUI still relevant in modern networks?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Despite newer 25G or 50G lane technologies, XLAUI remains widely used for legacy 40G deployments, high-density QSFP+ designs, and mixed-rate data center fabrics. It provides interoperability and a known electrical performance baseline.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" >8. How does LINK-PP implement XLAUI in their 40G QSFP+ modules?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><a target=\"_blank\" rel=\"\" href=\"https:\/\/www.l-p.com\/store-26153-40g-qsfp.htm\">LINK-PP\u2019s 40G QSFP+ modules<\/a> (e.g., LQ-CW40-LR4C) follow IEEE 802.3ba standards and implement electrical lanes equivalent to XLAUI for host-side connections. This ensures predictable performance and easier integration into switches or linecards supporting 10-lane XLAUI.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" >9. What design considerations should engineers keep in mind when deploying XLAUI?<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><p>Verify host ASIC supports 10-lane XLAUI.<\/p><\/li><li><p>Ensure channel insertion loss, return loss, and crosstalk meet standards.<\/p><\/li><li><p>Align SERDES lanes properly to avoid errors.<\/p><\/li><li><p>Consider thermal and power constraints in dense deployments.<\/p><\/li><li><p>Plan lane breakout paths for future upgrades (e.g., 100G or 400G).<\/p><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" >10. Can XLAUI interfaces be upgraded to higher speeds in the future?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Yes, but it requires careful planning. Future upgrades to CAUI or other higher-lane architectures may affect PCB routing, retimer requirements, and SERDES allocation. Proper design foresight ensures backward compatibility with <a target=\"_blank\" rel=\"\" href=\"https:\/\/www.l-p.com\/store-26153-40g-qsfp.htm\">40G QSFP+ modules.<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>XLAUI (10-Lane Attachment Unit Interface) enables high-speed, reliable connections between host chips and QSFP+ modules in 40\/100G Ethernet systems.<\/p>","protected":false},"author":1,"featured_media":3792,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[27],"tags":[18,26],"class_list":["post-3793","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-glossary","tag-40g-qsfp-transceivers","tag-optics-transceivers"],"blocksy_meta":[],"acf":[],"_links":{"self":[{"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/posts\/3793","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/comments?post=3793"}],"version-history":[{"count":2,"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/posts\/3793\/revisions"}],"predecessor-version":[{"id":7988,"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/posts\/3793\/revisions\/7988"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/media\/3792"}],"wp:attachment":[{"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/media?parent=3793"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/categories?post=3793"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lp.szlogic.cn\/ru\/wp-json\/wp\/v2\/tags?post=3793"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}