MPO Fiber Connector: Types, Polarity & Data Center Use
May 29, 2026
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Robin Zhao
Robin is professional writer focuing on structured cabling and optical communication
table Of contents
TL;DR: An MPO fiber connector (Multi-fiber Push-On) packs 8 to 72 fibers into one compact plug, making it the go-to choice for high-speed data centers running 40G, 100G, 400G, and 800G networks. Choosing the wrong type or polarity can bring an entire link down. This guide covers every MPO connector type, all three polarity methods, and the right cable for each application, so you can spec your next deployment with confidence.
A single connector. From 8 to 72 fibers. One push.
That's the core promise of the MPO fiber connector - and it's exactly why data centers worldwide are standardizing on it. But here's what most guides won't tell you: wrong polarity is the number-one cause of MPO link failure during installation. One wrong choice between Type A, B, or C polarity, and your entire high-speed run goes dark.
The global MPO connector market was valued at $3.8 billion in 2025 and is projected to reach $9.2 billion by 2034. That growth is driven almost entirely by the push from 100G to 400G and 800G Ethernet in AI data centers and cloud infrastructure. If you're a network engineer or procurement manager, MPO connectors aren't optional - they're the backbone of everything fast.
This guide breaks down what an MPO fiber connector is, the types available, how each polarity method works, and which cable to use for every speed scenario from 40G to 1.6T.
What Is an MPO Fiber Connector?
An MPO fiber connector is a high-density optical connector that terminates multiple fibers on a single precision-molded MT (Mechanical Transfer) ferrule. Unlike standard LC or SC connectors that handle one or two fibers, MPO connectors support 8 to 72 fibers in a single interface - making them essential for parallel optical transmission in modern networks.
MPO connectors comply with international standards IEC 61754-7 and TIA-604-5 (FOCIS 5), which guarantees interoperability between different manufacturers. That standardization is why MPO has become the default interface for every high-speed transceiver from QSFP+ to OSFP.
Every MPO connector has four key components:
MT Ferrule: Holds all fibers in a precisely aligned row.
Guide Pins: Two metal pins (male) or holes (female) that align mating connectors.
Keying Tab: A raised plastic tab that prevents incorrect insertion and controls fiber mapping.
White Dot: Marks fiber Position 1 for polarity identification and troubleshooting.
At COBTEL, we manufacture MPO patch cords with factory-polished ferrules and 100% optical testing before shipment - because connector quality at the ferrule level determines whether your link works on the first try.
MPO Connector Types: Which Fiber Count Do You Need?
MPO connectors come in five main fiber counts - MPO-8, MPO-12, MPO-16, MPO-24, and MPO-32+. The right count depends on the transceiver standard you're running.
Getting the fiber count wrong wastes fibers and money, or worse, forces you to re-cable when you upgrade speeds. Here's exactly how each type maps to real-world use:
MPO-8 holds 8 fibers (4 Tx, 4 Rx). It's used for 40GBASE-SR4 and 100GBASE-SR4 applications. When used on a 12-fiber ferrule, the outer 8 positions are active and the middle 4 are dark.
MPO-12 is the most common type in data centers today. It supports 40G SR4, 100G SR4, and can serve as a breakout source for multiple 10G or 25G duplex links. The 4 unused center fibers give you a built-in upgrade path.
MPO-16 is the right choice for 400GBASE-SR8 and 800GBASE-SR8. It carries 8 active lanes (8 Tx, 8 Rx) in a single row of 16 fibers. For new 400G and 800G builds, MPO-16 avoids the fiber waste that comes from using dual MPO-12 connectors in 8-lane applications.
MPO-24 uses two rows of 12 fibers each. It supports 100GBASE-SR10, 120G applications, or three simultaneous 40G links. High-density backbone trunks use MPO-24 to maximize fiber per conduit while keeping future flexibility.
MPO-32 and above (48, 60, 72 fibers) serve specialty hyperscale and optical switching environments. These are not common in standard data center deployments, but 1.6T applications will lean on MPO-32 as the standard matures.
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Type
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Fiber Count
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Key Applications
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|---|---|---|
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MPO-8
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8
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40G/100G SR4
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MPO-12
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12
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40G/100G/400G, general backbone
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|
MPO-16
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16
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400G SR8, 800G SR8
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|
MPO-24
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24
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100G SR10, high-density backbone
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|
MPO-32+
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32–72
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Hyperscale, 1.6T (emerging)
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Selection rule: For any new 400G or 800G SR deployment, start with MPO-16. For anything below 400G or any legacy migration, MPO-12 is the right base.
Male vs. Female Connectors and Key Orientation
Male MPO connectors have two guide pins extending from the ferrule. Female MPO connectors have two holes. All equipment ports (switches, transceivers) are male. Cables connecting to equipment must be female.
This is a point where mistakes happen in the field. The rule is simple:
Equipment ports (switches, QSFP transceivers, OSFP modules) are always male (pinned).
Patch cords and trunk cables connecting to equipment must have female (unpinned) connectors at the equipment end.
Cable-to-cable connections via MPO couplers use male on both cable ends with a female adapter in the middle.
Keying orientation matters just as much. Key orientation directly controls how fibers map through the connector, which feeds into the three polarity methods described in the next section.
Key-up: The keying tab faces upward when looking at the connector face.
Key-down: The keying tab faces downward.
Never mix key orientations randomly. Every polarity scheme defines exactly where each end should be keyed. Getting this wrong gives you a live link with crossed fibers - a problem that can take hours to find without proper documentation.
MPO vs. MTP: What's the Actual Difference?
MTP is a trademarked version of MPO made exclusively by US Conec. All MTP connectors are MPO-compliant, but MTP connectors exceed standard MPO specs with lower insertion loss, tighter tolerances, and longer mechanical life.
Here's the practical comparison:
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Feature
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Standard MPO
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MTP (Enhanced)
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|---|---|---|
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Typical Insertion Loss
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0.35–0.75 dB
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0.15–0.35 dB
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Elite Grade Loss
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None
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<0.20 dB
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Mating Cycles
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~500
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600+
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Guide Pins
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Standard metal
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Elliptical stainless steel
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Ferrule Design
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Fixed
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Floating (better alignment)
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Pin Clamp
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Plastic
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Metal
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Housing
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Fixed mold
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Removable for field cleaning
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MTP's floating ferrule reduces insertion loss by ensuring fiber tip contact even under slight misalignment. In a complex data center with 8 to 10 patch points per link, saving 0.20 dB per connector adds up fast.
When to use standard MPO:
Enterprise LANs with relaxed loss budgets
Moderate-density deployments below 40G
Budget-sensitive projects with low re-patching frequency
When to use MTP:
Hyperscale and cloud data centers with tight loss budgets
100G, 400G, 800G parallel optic links
Environments that need frequent re-patching and reconfiguration
Long-term infrastructure where reliability matters most
One critical note: if you mix MPO and MTP in the same link, the link performs at the lower-quality MPO spec. Use uniform connector types within any single channel.
MPO Polarity: The One Thing That Kills Links Most Often
MPO polarity defines how transmit (Tx) fibers on one end connect to receive (Rx) fibers on the other end. There are three standardized methods defined by TIA-568.3-D: Type A (straight-through), Type B (reversed), and Type C (pairs-swapped). Using the wrong type means Tx connects to Tx - and the link stays dark.
This is the most important section for installation teams. Wrong polarity is the most frequent cause of MPO link failure during deployment. Let's break each method down clearly.
Type A Polarity (Straight-Through)
Configuration: Fiber at Position 1 connects to Position 1 at the other end. No fiber crossing. The trunk cable uses key-up on one end and key-down on the other - the flip happens at the adapter.
Best for:
Modular cassette-based patch panel systems
Mixed-speed infrastructure that may upgrade from 10G to 40G or 100G over time
Point-to-point duplex links where patch cord flexibility is needed
Type A is the simplest to manufacture and stock. Its straight-through mapping makes it the easiest to document and the easiest to troubleshoot.
Type B Polarity (Reversed)
Configuration: Fiber at Position 1 connects to Position 12 at the other end. The full array is reversed. The trunk cable uses key-up on both ends - the built-in reversal corrects Tx to Rx alignment.
Best for:
All direct parallel optic connections (40G, 100G, 400G, 800G SR/DR)
Leaf-spine data center architectures
Direct connections to QSFP+, QSFP28, QSFP-DD, and OSFP transceivers
Type B is the standard polarity for all parallel optical transmission. Every modern high-speed transceiver expects it. Using Type A for parallel optics means Tx connects to Tx - the link will not come up, period.
Type C Polarity (Pairs-Swapped)
Configuration: Adjacent fiber pairs are swapped (1 to 2, 2 to 1, 3 to 4, 4 to 3, and so on). The cable looks like Type A externally but has a different internal mapping.
Best for:
MPO-to-LC duplex breakout systems
Certain legacy duplex applications
Type C sees very limited use in modern parallel optical deployments. If you're starting fresh with 40G or above, you most likely don't need it.
Polarity Selection Quick-Reference
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Application
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Use This Polarity
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Why
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|---|---|---|
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40G SR4
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Type B
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Parallel optics standard
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100G SR4
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Type B
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Parallel optics standard
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200G SR4
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Type B
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Parallel optics standard
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400G SR8 / DR4
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Type B
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Parallel optics standard
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800G SR8 / DR8
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Type B
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Parallel optics standard
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Cassette-based patch panels
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Type A
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Speed-agnostic flexibility
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MPO-to-LC breakout
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Type C or A
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Depends on breakout patch cord
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The golden rule: Pick one polarity standard for your entire facility and document every cable. Mixing Type A and Type B in the same infrastructure creates confusion and failures that take hours to find.
MPO Cable Types: Trunk, Breakout, and Patch
Choosing the right cable type matters as much as choosing the right connector type. MPO cables come in three main forms, each built for a different role in the cabling hierarchy.
Trunk Cables have MPO connectors on both ends and carry 8, 12, 16, 24, or 48 fibers. These run between patch panel zones: from the main distribution area (MDA) to the intermediate distribution area (IDA), between row-end switches, and across campus backbone runs. Factory pre-polishing gives you consistent insertion loss that field-termination can't match. Look for LSZH (Low Smoke Zero Halogen) jackets for plenum spaces and data centers.
Breakout (Fan-out) Cables start with one MPO on one end and split into individual connectors - usually LC duplex - on the other end. Common configurations:
MPO-8 to 4×LC duplex (converts one 40G link to four 10G links)
MPO-12 to 6×LC duplex (converts 100G to six 10G or three 40G links)
MPO-24 to 12×LC duplex (high-density server-to-switch connections)
Breakout cables reduce installation time by up to 75% compared to field-terminated duplex cabling, since the factory terminates all fibers before delivery. Polarity on breakout cables must match the trunk infrastructure - verify Type B compatibility if you're running parallel optics through a cassette-based patch system.
Patch Cords (Jumpers) are short MPO-to-MPO cables used for rack-level connections: switch-to-switch in leaf-spine fabrics, equipment-to-panel connections, and in-rack device links. Lengths from 1 to 5 meters cover most rack-scale scenarios. These are the cables most likely to be swapped during troubleshooting - make sure they're clearly labeled with polarity type.
Our fiber patch cord range includes single-mode and multimode options that pair with MPO patch cords for complete end-to-end solutions.
MPO Fiber Connectors in High-Speed Data Centers: 40G to 1.6T
MPO connectors are the required physical interface for every parallel optic standard from 40G to 800G and beyond. The specific MPO type, fiber count, and polish type change at each speed tier.
Here's how MPO fits into each generation of high-speed optics:
40G (40GBASE-SR4): 8 active fibers (4 Tx, 4 Rx) at 10 Gbps per lane. Uses MPO-8 or MPO-12 (outer 8 positions). UPC polish for multimode OM3/OM4. Maximum reach: 100 meters on OM4.
100G (100GBASE-SR4): 8 active fibers at 25 Gbps per lane. Same MPO-8 or MPO-12 footprint as 40G SR4. Drop-in compatible with existing MPO-12 infrastructure when using the outer 8 fibers. For 100GBASE-SR10 (10-lane), you need MPO-24 with all 20 active fibers.
400G (400GBASE-SR8): 16 active fibers at 50 Gbps per lane. MPO-16 is the native fit. Dual MPO-12 works but wastes 4 fibers per connector and adds a mating point. For new builds, MPO-16 is the right choice for 400G SR8. For 400GBASE-DR4 (single-mode, 500 m), use MPO-12 with APC polish.
800G (800GBASE-SR8): 16 active fibers at 100 Gbps per lane. Requires MPO-16 on multimode (OM4/OM5) or MPO-16 APC on single-mode (800G-DR8). 800G will be the fastest-growing data center speed segment in 2026 and 2027, with adoption accelerating in enterprise AI clusters.
1.6T and beyond: Emerging 1.6T standards will use 16 fibers at 200 Gbps per lane or 32 fibers at 100 Gbps per lane. MPO-24 and MPO-32 will carry this traffic. Deploying MPO-24 backbone infrastructure today gives you a clear upgrade path to 1.6T without re-cabling.
OSFP Transceiver Integration: OSFP (Octal Small Form-factor Pluggable) is the transceiver format for 800G and 1.6T. OSFP 800G ports use MPO-16. OSFP 1.6T ports will use MPO-16 (at 200G per lane) or MPO-32 (at 100G per lane). Our optical modules and DAC/AOC cables are designed to pair directly with MPO-based OSFP infrastructure.
A large cloud operator recently reported a 40% reduction in cabling volume by switching from dual MPO-12 to single MPO-16 systems for their 800G switch deployment - while reducing the number of mating points per link at the same time.
How to Choose the Right MPO Connector: A 5-Step Framework
Selecting the wrong MPO connector can mean re-cabling an entire data hall. Here's a clear framework for getting it right the first time:
Step 1: Confirm your transceiver standard. Start with the switch or server port. Is it QSFP28 (100G SR4), QSFP-DD (400G SR8), or OSFP (800G SR8)? The transceiver standard tells you the fiber count you need.
Step 2: Choose the fiber count. Map the transceiver to the MPO type: 8/12-fiber for 40G/100G SR4, 16-fiber for 400G/800G SR8, 24-fiber for 100G SR10 or high-density backbone.
Step 3: Set your polarity. For any direct parallel optic link (40G and above), use Type B. For cassette-based modular systems, use Type A. Document this decision and apply it uniformly across the facility.
Step 4: Select the polish type. Multimode (OM3/OM4/OM5) always uses UPC. Single-mode (OS2) used for DR, FR, or LR applications requires APC. Never mix APC and UPC connectors - the angled face will damage UPC ferrules.
Step 5: Verify the lifecycle cost. Standard MPO is fine for budget enterprise deployments. For 100G+, high-density, or frequently reconfigured environments, MTP's lower insertion loss and longer mating cycle life reduce total cost over a 5-to-10-year horizon.
Our optical communication product line covers all five dimensions above, and our team can help you validate your loss budget before you commit to a cabling design.
Conclusion
MPO fiber connectors are not complicated - but they do require the right decisions at each step. Choose the wrong fiber count and you waste port capacity. Choose the wrong polarity and you get a dark link. Choose the wrong polish type and you damage ferrules that cost hundreds to replace.
The three things to remember:
Match fiber count to your transceiver standard (MPO-16 for 400G/800G SR8, MPO-12 for everything else by default).
Use Type B polarity for all direct parallel optic links (40G and above).
Standardize your polarity choice across the entire facility and document every cable.
At COBTEL, we've spent 20 years manufacturing fiber optic connectivity solutions for data centers, telecom operators, and enterprise networks. We produce MPO patch cords with factory-level precision, matched to the exact specifications of your deployment.
Ready to spec your next MPO project? Fill out the inquiry form below and our technical team will review your requirements, validate your loss budget, and recommend the right solution for your speed tier and cabling architecture.
Frequently Asked Questions
What is an MPO fiber connector?
An MPO (Multi-fiber Push-On) fiber connector is a high-density optical connector that holds multiple fibers in a single precision-molded ferrule. It supports 8, 12, 16, 24, or more fibers in one plug, compared to 1 or 2 fibers in standard LC or SC connectors. MPO connectors follow IEC 61754-7 and TIA-604-5 standards and are the required interface for high-speed parallel optical transceivers from 40G to 800G and beyond.
What is the difference between MPO-12 and MPO-16?
MPO-12 has 12 fibers in a single row and is the most common type for 40G and 100G SR4 applications. MPO-16 has 16 fibers in a single row and is the native fit for 400GBASE-SR8 and 800GBASE-SR8, which use 8 transmit and 8 receive lanes. For new 400G and 800G builds, MPO-16 avoids the fiber waste that comes from using two MPO-12 connectors to serve an 8-lane transceiver.
What is MPO polarity and why does it matter?
MPO polarity defines how transmit (Tx) fibers at one end connect to receive (Rx) fibers at the other end. TIA-568.3-D defines three polarity methods: Type A (straight-through), Type B (reversed), and Type C (pairs-swapped). Wrong polarity means Tx connects to Tx, which prevents the link from activating. Type B is required for all direct parallel optic connections from 40G onward. Wrong polarity is the most common cause of new MPO link failures on the day of installation.
What is the difference between MPO and MTP connectors?
MPO is the industry-standard connector specification defined by IEC 61754-7 and produced by multiple manufacturers. MTP is a trademarked, high-performance MPO developed exclusively by US Conec. MTP connectors deliver typical insertion loss of 0.15–0.35 dB, compared to 0.35–0.75 dB for standard MPO, due to a floating ferrule, elliptical guide pins, and tighter manufacturing tolerances. All MTP connectors are MPO-compatible, but standard MPO connectors don't meet MTP performance levels.
Which MPO type do I need for 400G and 800G networks?
For 400GBASE-SR8 and 800GBASE-SR8 (multimode, short reach), you need MPO-16 with UPC polish. For 400GBASE-DR4 and 800GBASE-DR8 (single-mode, medium reach), you need MPO-12 or MPO-16 with APC polish. Use Type B polarity for all of these. 800G is the fastest-growing data center segment in 2025, and MPO-16 infrastructure deployed today will also support emerging 1.6T standards when OSFP transceivers mature.
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