{"id":12295,"date":"2026-05-19T11:10:03","date_gmt":"2026-05-19T03:10:03","guid":{"rendered":"https:\/\/ascentoptics.com\/blog\/?p=12295"},"modified":"2026-05-19T11:10:03","modified_gmt":"2026-05-19T03:10:03","slug":"400g-osfp-transceiver-types","status":"publish","type":"post","link":"https:\/\/ascentoptics.com\/blog\/400g-osfp-transceiver-types\/","title":{"rendered":"400G OSFP Transceiver Types: SR8 DR4 FR4 LR4 Guide"},"content":{"rendered":"<p>In February 2025, data center architect David was struggling to select optical modules for his 32-port 400G spine switch. The datasheets listed six variants \u2014 SR8, SR4, DR4, FR4, 2xFR4, and LR4. Each had different reach, fiber requirements, connectors, and pricing. After hours of comparing supplier datasheets, he still couldn\u2019t make a confident decision. He needed a clear, side-by-side guide covering all options.<\/p>\n<p>The 400G OSFP transceiver family provides a complete portfolio engineered for every reach and application in modern data center networks \u2014 from 50-meter NVIDIA InfiniBand links to 10km DCI metro connections.<\/p>\n<p>Whether you are planning a greenfield 400G deployment, upgrading from 100G QSFP28, or optimizing an existing fabric, understanding the differences between these six variants is essential. This guide walks you through each type with technical specifications, ideal applications, breakout options, and a practical selection framework.<\/p>\n<p><strong>Looking for the right 400G OSFP modules for your network?<\/strong>\u00a0<a href=\"https:\/\/ascentoptics.com\/400g-osfp\/\" target=\"_blank\" rel=\"noopener\"><u>Browse our 400G OSFP catalog<\/u><\/a>\u00a0for SR8, SR4, DR4, FR4, 2xFR4, and LR4 variants with platform-tested compatibility.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>400G OSFP Transceiver Types at a Glance<\/strong><\/h2>\n<p>The table below summarizes the major 400G OSFP module variants currently used in modern data center and AI networking environments.<\/p>\n<table style=\"height: 474px;\" width=\"912\">\n<tbody>\n<tr>\n<td width=\"137\"><strong><b>Module Type<\/b><\/strong><\/td>\n<td width=\"67\"><strong><b>Reach<\/b><\/strong><\/td>\n<td width=\"86\"><strong><b>Fiber<\/b><\/strong><\/td>\n<td width=\"134\"><strong><b>Connector<\/b><\/strong><\/td>\n<td width=\"64\"><strong><b>Power<\/b><\/strong><\/td>\n<td width=\"151\"><strong><b>Modulation<\/b><\/strong><\/td>\n<td width=\"210\"><strong><b>Application<\/b><\/strong><\/td>\n<\/tr>\n<tr>\n<td width=\"137\"><a href=\"https:\/\/ascentoptics.com\/product\/400g-osfp-sr8.html\" target=\"_blank\" rel=\"noopener\"><strong>OSFP SR8<\/strong><\/a><\/td>\n<td width=\"67\">100m<\/td>\n<td width=\"86\">OM4 MMF<\/td>\n<td width=\"134\">MTP\/MPO-16<\/td>\n<td width=\"64\">~10W<\/td>\n<td width=\"151\">8\u00d750G PAM4<\/td>\n<td width=\"210\">Intra-rack Ethernet<\/td>\n<\/tr>\n<tr>\n<td width=\"137\"><a href=\"https:\/\/ascentoptics.com\/product\/400g-osfp-sr4-850nm-100m-mpo-12-mmf-transceivers.html\" target=\"_blank\" rel=\"noopener\"><strong>OSFP SR4<\/strong><\/a><\/td>\n<td width=\"67\">100m<\/td>\n<td width=\"86\">OM4 MMF<\/td>\n<td width=\"134\">MPO-12 UPC<\/td>\n<td width=\"64\">~8.5W<\/td>\n<td width=\"151\">4x100G PAM4<\/td>\n<td width=\"210\">InfiniBand NDR<\/td>\n<\/tr>\n<tr>\n<td width=\"137\"><a href=\"https:\/\/ascentoptics.com\/product\/400gbe-osfp-dr4.html\" target=\"_blank\" rel=\"noopener\"><strong>OSFP DR4<\/strong><\/a><\/td>\n<td width=\"67\">500m<\/td>\n<td width=\"86\">OS2 SMF<\/td>\n<td width=\"134\">MPO-12 APC<\/td>\n<td width=\"64\">~10W<\/td>\n<td width=\"151\">4x100G PAM4<\/td>\n<td width=\"210\">Spine-leaf, campus<\/td>\n<\/tr>\n<tr>\n<td width=\"137\"><a href=\"https:\/\/ascentoptics.com\/product\/400g-osfp-fr4-2km.html\" target=\"_blank\" rel=\"noopener\"><strong>OSFP FR4<\/strong><\/a><\/td>\n<td width=\"67\">2km<\/td>\n<td width=\"86\">OS2 SMF<\/td>\n<td width=\"134\">Duplex LC<\/td>\n<td width=\"64\">~12W<\/td>\n<td width=\"151\">4\u00d7100G PAM4 LAN-WDM<\/td>\n<td width=\"210\">DCI short-haul<\/td>\n<\/tr>\n<tr>\n<td width=\"137\"><a href=\"https:\/\/ascentoptics.com\/product\/400gbe-osfp-fr4-lc.html\" target=\"_blank\" rel=\"noopener\"><strong>OSFP 2xFR4<\/strong><\/a><\/td>\n<td width=\"67\">2km<\/td>\n<td width=\"86\">OS2 SMF<\/td>\n<td width=\"134\">Dual duplex LC<\/td>\n<td width=\"64\">~14W<\/td>\n<td width=\"151\">2\u00d7200G FR4<\/td>\n<td width=\"210\">Cost-optimized DCI<\/td>\n<\/tr>\n<tr>\n<td width=\"137\"><a href=\"https:\/\/ascentoptics.com\/product\/400g-osfp-lr4.html\" target=\"_blank\" rel=\"noopener\"><strong>OSFP LR4<\/strong><\/a><\/td>\n<td width=\"67\">10km<\/td>\n<td width=\"86\">OS2 SMF<\/td>\n<td width=\"134\">Duplex LC<\/td>\n<td width=\"64\">~12W<\/td>\n<td width=\"151\">4\u00d7100G PAM4 LAN-WDM<\/td>\n<td width=\"210\">Metro aggregation<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-12301 aligncenter\" src=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-Module-Types-Comparison.png\" alt=\"400G OSFP Module Types Comparison\" width=\"684\" height=\"484\" srcset=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-Module-Types-Comparison.png 1491w, https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-Module-Types-Comparison-283x200.png 283w\" sizes=\"auto, (max-width: 684px) 100vw, 684px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Several clear patterns emerge from this comparison.<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Multimode variants such as SR8 and SR4 are designed for short-reach intra-data-center connectivity.<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Single-mode modules extend transmission reach from 500 meters with DR4 up to 10 kilometers with LR4.<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Parallel optics modules typically use MPO connectors, while wavelength-multiplexed modules use duplex LC interfaces to minimize fiber consumption.<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>The correct module depends on the specific combination of reach, protocol, switch platform, and existing fiber infrastructure.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>400G OSFP SR8: Short-Reach Multimode (100m)<\/strong><\/h2>\n<p>The OSFP SR8 is the standard short-reach multimode module for 400G Ethernet networks. This module has eight 53.125 Gbps PAM4 electrical lanes that align with eight 850nm VCSEL optical lanes, appealing to 400 Gbps over multimode fiber.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Electrical and Optical Architecture<\/strong><\/h3>\n<p>OSFP SR8 uses:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>8 electrical lanes<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>8 optical transmit lanes<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>8 optical receive lanes<\/li>\n<\/ul>\n<p>Each lane operates at 53.125 GBaud PAM4, delivering an effective data rate of 100Gbps per lane pair.<\/p>\n<p>&nbsp;<\/p>\n<p>On the optical side, the module uses:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>850nm VCSEL transmitters<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>PIN photodetectors for reception<\/li>\n<\/ul>\n<p>This parallel optics architecture avoids wavelength multiplexing complexity and keeps latency and module cost relatively low.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Reach and Fiber Type<\/strong><\/h3>\n<p>Regarding the possible link spans, OSFP SR8 supports up to 70 meters over OM3 and 100 meters over OM4 multimode fiber. Some manufacturers extended OM4 range to 150 meters through the use of improved link budgets, but 100 m is the IEEE 802.3bs standard.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Applications<\/strong><\/h3>\n<p>For intra-rack switch-switch links and very short leaf-spine interconnects within the same row, SR8 is unmatched. For AI and HPC clusters that are using Ethernet (as opposed to InfiniBand), SR8 is preferred to links between a ToR switch and a spine switch down the same hot aisle.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Breakout Capability<\/strong><\/h3>\n<p>OSFP SR8 commonly supports breakout into 4\u00d7100G SR2 or 8\u00d750G connections, depending on switch ASIC support.\u00a0Some platforms also support 2\u00d7200G SR4 breakout configurations.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Flat-Top vs Finned-Top Variants<\/strong><\/h3>\n<p>OSFP SR8 modules are available in two thermal formats:<\/p>\n<ul>\n<li><b><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong><\/b><strong><b>Flat-top modules<\/b><\/strong>, which rely on the switch riding heatsink (RHS)<\/li>\n<li><b><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong><\/b><strong><b>Finned-top modules<\/b><\/strong>, which include an integrated heatsink (IHS)<\/li>\n<\/ul>\n<p>Finned-top modules are typically preferred in high-power switch environments where airflow and thermal density are more demanding.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>400G OSFP SR4: NVIDIA InfiniBand NDR Optics<\/strong><\/h2>\n<p>OSFP SR4 is primarily associated with NVIDIA InfiniBand NDR deployments. While physically similar to SR8, SR4 uses a different lane architecture optimized for NVIDIA\u2019s 4\u00d7100G PAM4 InfiniBand design.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong><b>4x100G PAM4 Architecture<\/b><\/strong><\/h3>\n<p>Contrary to the eight 50G lanes on the SR8, the OSFP SR4 deploys four 100 Gbps PAM4 lanes. Each lane operates at 53.125 GBaud using PAM4 signaling.\u00a0This architecture aligns with NVIDIA ConnectX-7 adapters, BlueField DPUs, and Quantum-2 InfiniBand switches.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>MPO-12 Interface<\/strong><\/h3>\n<p>SR4 uses an MPO-12 UPC connector instead of MPO-16.\u00a0This difference is important during structured cabling planning because SR4 and SR8 are not directly interchangeable at the cabling layer.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Deployment Scenarios<\/strong><\/h3>\n<p>OSFP SR4 is commonly used in:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>NVIDIA Quantum-2 fabrics<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>AI training clusters<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>HPC supercomputing environments<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>GPU-to-switch interconnects<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>InfiniBand NDR deployments<\/li>\n<\/ul>\n<p>For NVIDIA-specific deployment guidance, see our OSFP for NVIDIA InfiniBand NDR Guide.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-12303 aligncenter\" src=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-SR4-transceiver-for-InfiniBand-NDR-AI-cluster-1.png\" alt=\"400G OSFP SR4 transceiver for InfiniBand NDR AI cluster\" width=\"690\" height=\"388\" srcset=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-SR4-transceiver-for-InfiniBand-NDR-AI-cluster-1.png 1672w, https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-SR4-transceiver-for-InfiniBand-NDR-AI-cluster-1-355x200.png 355w, https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-SR4-transceiver-for-InfiniBand-NDR-AI-cluster-1-1024x576.png 1024w, https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-SR4-transceiver-for-InfiniBand-NDR-AI-cluster-1-178x100.png 178w, https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-SR4-transceiver-for-InfiniBand-NDR-AI-cluster-1-768x432.png 768w\" sizes=\"auto, (max-width: 690px) 100vw, 690px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>NVIDIA Compatibility<\/strong><\/h3>\n<p>NVIDIA commonly references SR4 modules using part numbers such as:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>MMA1Z00-NS400<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>MMA4Z00-NS (switch-side twin-port versions)<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>When deploying third-party optics, platform validation is strongly recommended. For deeper InfiniBand-specific guidance, see our\u00a0<a href=\"https:\/\/ascentoptics.com\/blog\/osfp-nvidia-infiniband-ndr\/\" target=\"_blank\" rel=\"noopener\"><u>OSFP for NVIDIA InfiniBand NDR guide<\/u><\/a>.<\/p>\n<p><strong>Need OSFP SR4 modules tested for NVIDIA ConnectX-7?<\/strong>\u00a0<a href=\"https:\/\/ascentoptics.com\/contact-us.html\" target=\"_blank\"><u>Contact our optical engineers<\/u><\/a>\u00a0for platform compatibility verification.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>400G OSFP DR4: 500m Single-Mode Connectivity<\/strong><\/h2>\n<p>The OSFP DR4 is the most versatile 400G OSFP module\u00a0for modern data center architectures.\u00a0It transmits 4x100G PAM4 over single-mode fiber, reaching 500 meters with no optical amplification.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Architecture and Specifications<\/strong><\/h3>\n<p>DR4 transmits:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>4\u00d7100G PAM4 optical signals<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>over single-mode fiber<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>at 1310nm wavelengths<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>The module uses an MPO-12 APC connector with:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>4 transmit fibers<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>4 receive fibers<\/li>\n<\/ul>\n<p>for a total of 8 active fibers.<\/p>\n<p>Like most 100G-per-lane PAM4 optics, DR4 requires KP4 forward error correction (FEC) to maintain signal integrity and BER performance.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Spine-Leaf and Campus Applications<\/strong><\/h3>\n<p>OSFP DR4 is there to be in a spine-leaf architecture where racks are situated too far apart for multimode reach along with catering to last-row-to-last-row connections and point-to-point connections to campus buildings within up to 500 meters.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Breakout to 4x100G DR<\/strong><\/h3>\n<p>One of the standout feature advancements is breakout. Using an MPO-12 to 4\u00d7 duplex LC breakout harness,\u00a0one 400G DR4 port can connect to four 100G DR links.\u00a0This significantly improves port efficiency during 100G-to-400G migration.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-12304 aligncenter\" src=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-DR4-breakout-to-four-100G-DR-links.png\" alt=\"400G OSFP DR4 breakout to four 100G DR links\" width=\"674\" height=\"379\" srcset=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-DR4-breakout-to-four-100G-DR-links.png 1672w, https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-DR4-breakout-to-four-100G-DR-links-355x200.png 355w\" sizes=\"auto, (max-width: 674px) 100vw, 674px\" \/><\/p>\n<p>&nbsp;<\/p>\n<h2><strong>400G OSFP FR4: 2km Duplex LC Optics<\/strong><\/h2>\n<p>OSFP FR4 extends 400G connectivity to 2 kilometers while using only a duplex LC fiber pair.\u00a0This makes it highly attractive for environments with limited fiber availability.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>LAN-WDM Optical Architecture<\/strong><\/h3>\n<p>FR4 multiplexes four 100G PAM4 wavelengths onto a single duplex fiber pair using LAN-WDM technology. It puts four wavelengths, 1271 nm, 1291 nm, 1311 nm, and 1331 nm, on one fiber pair. An offer of 100 Gbps PAM4 per wavelength results in an aggregated 400G.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Duplex LC Connector<\/strong><\/h3>\n<p>The most outstanding advantage of FR4 over DR4 is that it uses duplex LC connectors. While DR4 requires MPO-12 (8 fibers active), FR4 requires just 2 fibers. For data centers with existing duplex LC infrastructure, FR4 often reduces deployment complexity and cabling cost.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Typical Applications<\/strong><\/h3>\n<p>FR4 is commonly used for:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Data center interconnect (DCI)<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Campus backbone links<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Enterprise WAN aggregation<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Cloud edge interconnects<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Metro-access connectivity<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3><strong>Breakout Considerations<\/strong><\/h3>\n<p>Physical optical breakout is generally not supported for FR4 because all wavelengths are multiplexed onto a single fiber pair.\u00a0If 4\u00d7100G breakout is required, DR4 is typically the preferred architecture.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>400G OSFP 2xFR4: Cost-Optimized Dual 200G<\/strong><\/h2>\n<p>2\u00d7FR4 differs from the other modules in this guide because it is primarily used in 800G environments rather than standard standalone 400G switching.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Dual 200G FR4 Structure<\/strong><\/h3>\n<p>A 2\u00d7FR4 module contains:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>two independent 200G FR4 interfaces<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>each using 4\u00d750G PAM4 wavelengths<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>The module typically exposes:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>dual duplex LC connectors<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>two separate 200G channels<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3><strong>Typical Use Cases<\/strong><\/h3>\n<p>2\u00d7FR4 is commonly used for:<\/p>\n<ul>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>800G switch breakout<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Dual 400G aggregation<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Metro DCI architectures<\/li>\n<li><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong>Flexible 800G fan-out deployments<\/li>\n<\/ul>\n<p>Because it consolidates multiple links into a single module, it can improve switch port utilization in high-density environments.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Power and Thermal Characteristics<\/strong><\/h3>\n<p>2\u00d7FR4 modules are among the highest-power OSFP optics currently deployed, typically operating between\u00a014W and 18W. Thermal planning is especially important in fully populated AI switch systems.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-12307 aligncenter\" src=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-2xFR4-dual-200G-FR4-architecture.png\" alt=\"400G OSFP 2xFR4 dual 200G FR4 architecture\" width=\"683\" height=\"384\" srcset=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-2xFR4-dual-200G-FR4-architecture.png 1672w, https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/400G-OSFP-2xFR4-dual-200G-FR4-architecture-355x200.png 355w\" sizes=\"auto, (max-width: 683px) 100vw, 683px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>400G OSFP LR4: 10km Metro Reach<\/strong><\/h2>\n<p>OSFP LR4 extends 400G transmission reach up to 10 kilometers over single-mode fiber.\u00a0It is designed for longer-distance enterprise and metro connectivity where FR4 reach is insufficient.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Extended-Reach LAN-WDM<\/strong><\/h3>\n<p>LR4 uses the same general wavelength approach as FR4 but with\u00a0higher optical launch power,\u00a0improved receiver sensitivity\u00a0and larger optical link budget. This enables stable transmission across longer fiber spans.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Applications<\/strong><\/h3>\n<p>OSFP LR4 rules the metro Ethernet aggregation, 5G transport network (backhaul, midhaul), and binds up regional data center interconnects. It&#8217;s useful for inter-building WAN connections in campuses, corporate setups, and selected government facilities.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Link Budget Considerations<\/strong><\/h3>\n<p>At 10km distances, optical budget planning becomes increasingly important. Standard single-mode fiber attenuation is approximately 0.25 dB\/km at 1310 nm.\u00a0After accounting for: connector loss, splice loss and patch panel loss, most LR4 deployments still maintain sufficient operating margin under normal fiber conditions.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>How to Choose the Right 400G OSFP Module<\/strong><\/h2>\n<p>Selecting the correct 400G OSFP module becomes much easier when approached step by step.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-12305 aligncenter\" src=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/How-to-choose-the-right-400G-OSFP-transceiver-module.png\" alt=\"How to choose the right 400G OSFP transceiver module\" width=\"662\" height=\"497\" srcset=\"https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/How-to-choose-the-right-400G-OSFP-transceiver-module.png 1448w, https:\/\/ascentoptics.com\/blog\/wp-content\/uploads\/2026\/05\/How-to-choose-the-right-400G-OSFP-transceiver-module-267x200.png 267w\" sizes=\"auto, (max-width: 662px) 100vw, 662px\" \/><\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Distance-Based Selection<\/strong><\/h3>\n<p>Reach is the primary selection criterion:<\/p>\n<ul>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>0-50m<\/strong>: OSFP SR4 (if InfiniBand) or OSFP SR8 (if Ethernet)<\/li>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>50-100m<\/strong>: OSFP SR8 (Ethernet only)<\/li>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>100m-500m<\/strong>: OSFP DR4<\/li>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>500m-2km<\/strong>: OSFP FR4 (single 400G) or OSFP 2xFR4 (dual 200G)<\/li>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>2km-10km<\/strong>: OSFP LR4<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3><strong><b>Fiber Infrastructure Considerations<\/b><\/strong><\/h3>\n<p>Existing fiber plant constrains your options:<\/p>\n<ul>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>OM3 \/ OM4 multimode fiber<\/strong>: SR4 or SR8 only<\/li>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>OS2 single-mode with MPO-12 infrastructure<\/strong>: DR4<\/li>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>OS2 single-mode with duplex LC infrastructure<\/strong>: FR4, 2xFR4, or LR4<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3><strong><b>Protocol Match: InfiniBand vs Ethernet<\/b><\/strong><\/h3>\n<p>A short reach of 50 meters with NVIDIA InfiniBand NDR deployments, SR4 OSFP is required. Ethernet deployments use SR8 for the same range.<\/p>\n<p>For a long reach, the SR4\/SR8 distinction is less relevant as beyond DR4. DR4, FR4, and LR4 are widely used for both Ethernet and InfiniBand environments, depending on platform support.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong><b>Power and Thermal Budget<\/b><\/strong><\/h3>\n<p>The module consumes as much as 14W (2xFR4) in power, and as little as 8.5W (SR4). Thus, a fully loaded switch of 32 ports would need about 270W to 450W in power consumption by all of its optics. Verify the power and cooling budgets of your switch before going for a high-power variant like 2xFR4.<\/p>\n<p>&nbsp;<\/p>\n<h3><strong><b>4-Step Decision Framework<\/b><\/strong><\/h3>\n<p>A pragmatic approach to selection:<\/p>\n<ol>\n<li><strong>1. Determine your reach requirement<\/strong>from the table above<\/li>\n<li><strong>2. Check your fiber infrastructure<\/strong>(multimode vs single-mode, MPO vs LC)<\/li>\n<li><strong>3. Identify your protocol<\/strong>(Ethernet, InfiniBand NDR, or both)<\/li>\n<li><strong>4. Verify platform compatibility<\/strong>with your switch vendor<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n<p>David, from our opening scenario, ended up specifying a mix: OSFP DR4 for 16 cross-row links (500m), OSFP SR8 for 12 intra-row leaf connections (under 100m), and OSFP FR4 for 4 DCI uplinks (2km). The blended approach reduced his total optics cost by 28% versus a uniform DR4 deployment while matching each port to its actual requirement.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Want a platform-specific recommendation for your 400G deployment?<\/strong>\u00a0<a href=\"https:\/\/ascentoptics.com\/contact-us.html\" target=\"_blank\"><u>Request a quote<\/u><\/a>\u00a0and our engineers will review your switch model, link distances, and protocol requirements.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>Power Consumption Across 400G OSFP Variants<\/strong><\/h2>\n<p>Power planning is critical for dense 400G deployments. Here is the complete power comparison:<\/p>\n<table>\n<tbody>\n<tr>\n<td width=\"154\"><strong><b>Module Type<\/b><\/strong><\/td>\n<td width=\"168\"><strong><b>Typical Power<\/b><\/strong><\/td>\n<td width=\"163\"><strong><b>Max Power<\/b><\/strong><\/td>\n<td width=\"267\"><strong><b>Thermal Variant<\/b><\/strong><\/td>\n<\/tr>\n<tr>\n<td width=\"154\">OSFP SR4<\/td>\n<td width=\"168\">8.5W<\/td>\n<td width=\"163\">10W<\/td>\n<td width=\"267\">Flat-top or Finned-top<\/td>\n<\/tr>\n<tr>\n<td width=\"154\">OSFP SR8<\/td>\n<td width=\"168\">10W<\/td>\n<td width=\"163\">12W<\/td>\n<td width=\"267\">Flat-top or Finned-top<\/td>\n<\/tr>\n<tr>\n<td width=\"154\">OSFP DR4<\/td>\n<td width=\"168\">10W<\/td>\n<td width=\"163\">12W<\/td>\n<td width=\"267\">Flat-top or Finned-top<\/td>\n<\/tr>\n<tr>\n<td width=\"154\">OSFP FR4<\/td>\n<td width=\"168\">12W<\/td>\n<td width=\"163\">14W<\/td>\n<td width=\"267\">Flat-top or Finned-top<\/td>\n<\/tr>\n<tr>\n<td width=\"154\">OSFP 2xFR4<\/td>\n<td width=\"168\">14W<\/td>\n<td width=\"163\">18W<\/td>\n<td width=\"267\">Finned-top recommended<\/td>\n<\/tr>\n<tr>\n<td width=\"154\">OSFP LR4<\/td>\n<td width=\"168\">12W<\/td>\n<td width=\"163\">14W<\/td>\n<td width=\"267\">Flat-top or Finned-top<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n<p>For a 32-port switch fully populated with high-power 2xFR4 modules, total optics power approaches 450W. Add the switch base power (200-400W) and a single 1U switch can draw 850W just for the data plane. AI infrastructure deployments with multiple 400G switches per rack need careful power and cooling planning.<\/p>\n<p>For broader context on form factor decisions, see our\u00a0<a href=\"https:\/\/ascentoptics.com\/blog\/osfp-vs-qsfp-dd\/\" target=\"_blank\" rel=\"noopener\"><u>QSFP-DD vs OSFP comparison guide<\/u><\/a>\u00a0covering the trade-offs between competing 400G architectures.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>Conclusion<\/strong><\/h2>\n<p>The 400G OSFP transceiver types form a complete portfolio designed for every modern networking application. Whether you are building an AI training cluster with NVIDIA InfiniBand, expanding a hyperscale spine-leaf fabric, or extending metro DCI capacity, there is a specific 400G OSFP variant engineered for the job.<\/p>\n<p>&nbsp;<\/p>\n<p>Key takeaways include:<\/p>\n<ul>\n<li><b><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong><\/b><strong><b>SR8 is widely used for short-reach 400G Ethernet connectivity<\/b><\/strong><\/li>\n<li><b><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong><\/b><strong><b>SR4 is optimized for NVIDIA InfiniBand NDR fabrics<\/b><\/strong><\/li>\n<li><b><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong><\/b><strong><b>DR4 provides flexible 500m single-mode connectivity with breakout support<\/b><\/strong><\/li>\n<li><b><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong><\/b><strong><b>FR4 reduces fiber consumption for 2km duplex LC deployments<\/b><\/strong><\/li>\n<li><b><strong data-start=\"2814\" data-end=\"2826\"><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span><\/strong><\/b><strong><b>LR4 enables 10km metro and enterprise connectivity<\/b><\/strong><\/li>\n<li><strong><span style=\"display: inline-block; margin: 0 8px;\">\u2022<\/span>2\u00d7FR4 supports flexible breakout architectures in emerging 800G environments<\/strong><\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>The best module is not necessarily the longest reach or highest specification\u2014it is the module that best matches your actual network architecture, cabling infrastructure, and future scalability requirements.<\/p>\n<p><strong>Ready to source 400G OSFP transceivers?<\/strong>\u00a0Contact AscentOptics for SR8, SR4, DR4, FR4, 2xFR4, and LR4 modules with platform validation, MSA compliance, and factory-direct pricing for deployments at any scale.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong><b>Frequently Asked Questions (FAQs)<\/b><\/strong><\/h2>\n<h3><strong><b>Q1: What is the difference between OSFP SR8 and SR4??<\/b><\/strong><\/h3>\n<p>OSFP SR8 uses eight 50G PAM4 optical lanes and is primarily deployed in 400G Ethernet environments. OSFP SR4 uses four 100G PAM4 lanes and is commonly used in NVIDIA InfiniBand NDR deployments.<\/p>\n<h3><strong><b>Q2: Which 400G OSFP module supports the longest distance?<\/b><\/strong><\/h3>\n<p>OSFP LR4 supports transmission distances up to 10 kilometers over single-mode fiber and is commonly used for metro aggregation and long-distance enterprise connectivity.<\/p>\n<h3><strong><b>Q3: Can 400G DR4 break out to 100G connections?<\/b><\/strong><\/h3>\n<p>Yes. A 400G DR4 port can typically break out into four independent 100G DR connections using an MPO-12 to 4\u00d7 duplex LC breakout harness.<\/p>\n<h3><strong><b>Q4: Is OSFP better than QSFP-DD for AI networks?<\/b><\/strong><\/h3>\n<p>OSFP generally provides higher thermal headroom and improved power handling compared with QSFP-DD, making it popular in AI and HPC deployments, especially in NVIDIA-based environments.<\/p>\n<p><strong><b>Q5\uff1a<\/b><\/strong><strong><b>Which 400G OSFP module uses the fewest fibers?<\/b><\/strong><\/p>\n<p>FR4 and LR4 use duplex LC connectors and require only two fibers, making them more fiber-efficient than parallel-optics modules such as SR8 and DR4.<\/p>\n<p>&nbsp;<\/p>\n<p><a href=\"https:\/\/osfpmsa.org\/\" target=\"_blank\" rel=\"nofollow noopener\">OSFP MSA<\/a><\/p>\n<p><a href=\"https:\/\/standards.ieee.org\/ieee\/802.3bs\/6748\/\" target=\"_blank\" rel=\"nofollow noopener\">IEEE 802.3bs<\/a><\/p>\n<p><a href=\"https:\/\/standards.ieee.org\/ieee\/802.3cu\/7515\/\" target=\"_blank\" rel=\"nofollow noopener\">IEEE 802.3cu<\/a><\/p>\n<p><a href=\"https:\/\/docs.nvidia.com\/networking\/display\/mlnxofedv493150\/infiniband+network\" target=\"_blank\" rel=\"nofollow noopener\">NVIDIA InfiniBand documentation<\/a><\/p>\n<p>&nbsp;<\/p>\n<style>\r\n.lwrp.link-whisper-related-posts{\r\n            \r\n            margin-top: 22px;\nmargin-bottom: 12px;\r\n        }\r\n        .lwrp .lwrp-title{\r\n            \r\n            \r\n        }.lwrp .lwrp-description{\r\n            \r\n            \r\n\r\n        }\r\n        .lwrp .lwrp-list-container{\r\n        }\r\n        .lwrp .lwrp-list-multi-container{\r\n            display: flex;\r\n        }\r\n        .lwrp .lwrp-list-double{\r\n            width: 48%;\r\n        }\r\n        .lwrp .lwrp-list-triple{\r\n            width: 32%;\r\n        }\r\n        .lwrp .lwrp-list-row-container{\r\n            display: flex;\r\n            justify-content: space-between;\r\n        }\r\n        .lwrp .lwrp-list-row-container .lwrp-list-item{\r\n            width: calc(50% - 20px);\r\n        }\r\n        .lwrp .lwrp-list-item:not(.lwrp-no-posts-message-item){\r\n            \r\n            margin-top: 11px;\nmargin-right: 16px;\nmargin-bottom: 15px;\nmargin-left: 9px;\r\n        }\r\n        .lwrp .lwrp-list-item img{\r\n            max-width: 100%;\r\n            height: auto;\r\n            object-fit: cover;\r\n            aspect-ratio: 1 \/ 1;\r\n        }\r\n        .lwrp .lwrp-list-item.lwrp-empty-list-item{\r\n            background: initial !important;\r\n        }\r\n        .lwrp .lwrp-list-item .lwrp-list-link .lwrp-list-link-title-text,\r\n        .lwrp .lwrp-list-item .lwrp-list-no-posts-message{\r\n            \r\n            \r\n            \r\n            \r\n        }@media screen and (max-width: 480px) {\r\n            .lwrp.link-whisper-related-posts{\r\n                \r\n                \r\n            }\r\n            .lwrp .lwrp-title{\r\n                \r\n                \r\n            }.lwrp .lwrp-description{\r\n                \r\n                \r\n            }\r\n            .lwrp .lwrp-list-multi-container{\r\n                flex-direction: column;\r\n            }\r\n            .lwrp .lwrp-list-multi-container ul.lwrp-list{\r\n                margin-top: 0px;\r\n                margin-bottom: 0px;\r\n                padding-top: 0px;\r\n                padding-bottom: 0px;\r\n            }\r\n            .lwrp .lwrp-list-double,\r\n            .lwrp .lwrp-list-triple{\r\n                width: 100%;\r\n            }\r\n            .lwrp .lwrp-list-row-container{\r\n                justify-content: initial;\r\n                flex-direction: column;\r\n            }\r\n            .lwrp .lwrp-list-row-container .lwrp-list-item{\r\n                width: 100%;\r\n            }\r\n            .lwrp .lwrp-list-item:not(.lwrp-no-posts-message-item){\r\n                \r\n                \r\n            }\r\n            .lwrp .lwrp-list-item .lwrp-list-link .lwrp-list-link-title-text,\r\n            .lwrp .lwrp-list-item .lwrp-list-no-posts-message{\r\n                \r\n                \r\n                \r\n                \r\n            };\r\n        }<\/style>\r\n<div id=\"link-whisper-related-posts-widget\" class=\"link-whisper-related-posts lwrp\">\r\n            <h3 class=\"lwrp-title\">Related Posts<\/h3>    \r\n        <div class=\"lwrp-list-container\">\r\n                                <div class=\"lwrp-list lwrp-list-row-container lwrp-list-double-row\">\r\n                <div class=\"lwrp-list-item\"><a href=\"https:\/\/ascentoptics.com\/blog\/osfp-nvidia-infiniband-ndr\/\" class=\"lwrp-list-link\"><span class=\"lwrp-list-link-title-text\">OSFP NVIDIA InfiniBand: ConnectX-7 &#038; Quantum-2 Guide<\/span><\/a><\/div><div class=\"lwrp-list-item\"><a href=\"https:\/\/ascentoptics.com\/blog\/qsfp-dd-vs-osfp-comparison\/\" class=\"lwrp-list-link\"><span class=\"lwrp-list-link-title-text\">QSFP-DD vs OSFP: The Critical 400G\/800G Form Factor Decision for Next-Generation Networks<\/span><\/a><\/div>                <\/div>\r\n                            <div class=\"lwrp-list lwrp-list-row-container lwrp-list-double-row\">\r\n                <div class=\"lwrp-list-item\"><a href=\"https:\/\/ascentoptics.com\/blog\/1-6t-osfp-xd-next-gen-data-center-optical-module\/\" class=\"lwrp-list-link\"><span class=\"lwrp-list-link-title-text\">1.6T OSFP-XD: Next-Gen Data Center Optical Module<\/span><\/a><\/div><div class=\"lwrp-list-item\"><a href=\"https:\/\/ascentoptics.com\/blog\/osfp-transceivers\/\" class=\"lwrp-list-link\"><span class=\"lwrp-list-link-title-text\">Finned-Top vs Flat-Top OSFP: How to Choose for 400G\/800G Data Centers<\/span><\/a><\/div>                <\/div>\r\n                <\/div>\r\n<\/div>","protected":false},"excerpt":{"rendered":"<p>In February 2025, data center architect David was struggling to select optical modules for his 32-port 400G spine switch. The datasheets listed six variants \u2014 SR8, SR4, DR4, FR4, 2xFR4, and LR4. Each had different reach, fiber requirements, connectors, and pricing. After hours of comparing supplier datasheets, he still couldn\u2019t make a confident decision. He [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":12297,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_wpscp_schedule_draft_date":"","_wpscp_schedule_republish_date":"","_wpscppro_advance_schedule":false,"_wpscppro_advance_schedule_date":"","_wpscppro_custom_social_share_image":0,"_facebook_share_type":"default","_twitter_share_type":"default","_linkedin_share_type":"default","_pinterest_share_type":"default","_linkedin_share_type_page":"","_instagram_share_type":"default","_selected_social_profile":null},"categories":[30,19],"tags":[],"class_list":["post-12295","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-optical-transceivers-technology","category-products"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v20.7 (Yoast SEO v22.6) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>400G OSFP Transceiver Types: SR8 DR4 FR4 LR4 Guide - AscentOptics Blog<\/title>\n<meta name=\"description\" content=\"Compare all 400G OSFP transceiver types: SR8, SR4, DR4, FR4, 2xFR4, LR4. 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