Standard 25G SFP28 AOCs were not designed for continuous operation inside a dielectric coolant tank. If coolant penetrates the optical engine, affects sealing materials, or degrades the cable jacket, the result may be link instability, increased bit-error rates, downtime, and higher tank-maintenance costs. A purpose-built 25G SFP28 immersion cooling AOC is engineered with fluid-resistant materials, enhanced module sealing, and an optical assembly designed for continuous operation in qualified single-phase or two-phase immersion environments.
Why Standard 25G AOCs Risk Your Immersion Cooling Deployment
Immersion cooling significantly increases the heat-removal capacity of high-density racks, but it also exposes every submerged interconnect to chemicals and operating conditions for which standard data center cables may not have been designed.
Conventional 25G SFP28 AOCs typically use cable jackets, adhesives, seals, optical materials, and module housings intended for air-cooled environments. During prolonged exposure to dielectric fluid, incompatible materials may soften, swell, shrink, become brittle, or release chemical compounds into the coolant. If fluid enters the optical engine or affects internal optical materials, optical coupling efficiency and link margin may decrease.
The result is not always an immediate hard failure. Engineers may instead experience intermittent link flaps, increased bit-error rates, reduced optical margin, or unstable receiver performance. These symptoms can be difficult to trace back to the cable. By the time the root cause is identified, the tank may already have been drained, components replaced, and valuable uptime lost.
A purpose-built 25G SFP28 immersion cooling AOC reduces these risks. It uses fluid-compatible cable materials, sealed module construction, and optical and electrical components qualified for continuous submersion in approved dielectric coolants. This helps maintain stable 25GbE connectivity inside the immersion tank.
What Makes FiberMall 25G SFP28 Immersion Cooling AOCs Different
FiberMall immersion-ready AOCs are designed for the same 25GbE applications as standard SFP28 AOCs, but the materials and mechanical structure are selected specifically for dielectric-fluid exposure.
Each cable terminates in sealed SFP28 modules designed to limit fluid ingress while retaining the plug-and-play advantages of a factory-terminated active optical cable.
Key Benefits
• Coolant-qualified construction — Available for use with selected PAO-based fluids, silicone oils, synthetic esters, mineral oils, and fluorinated dielectric fluids. Compatibility must be confirmed according to the exact coolant brand, fluid grade, operating temperature, and required exposure duration.
• Switch interoperability testing before shipment — Cables can be coded and tested for selected Cisco, Arista, Juniper, NVIDIA Networking, H3C, HPE Aruba, and Ruijie platforms. Compatibility is confirmed according to the exact switch model, operating-system version, port configuration, and EEPROM coding profile.
• Custom coding and cable lengths — Available with platform-specific EEPROM coding, dual-vendor coding, private labeling, and custom lengths from 1 meter to 100 meters.
• Factory-direct supply — OEM-compatible 25G interconnects are supplied directly without traditional distributor markups.
Whether you are connecting servers inside a single-phase oil bath or deploying auxiliary network links in a two-phase fluorinated-fluid system, these cables are designed to maintain stable electrical and optical performance during continuous coolant exposure.
FiberMall 25G SFP28 Immersion Cooling AOC Specifications
The FiberMall 25G SFP28 immersion cooling AOC uses an SFP28 connector at each end and supports a host data rate of 25.78125 Gb/s per direction.
Its primary application is 25 Gigabit Ethernet. InfiniBand EDR or other protocol support may be available on separately qualified configurations. Fibre Channel compatibility should only be claimed for a specific part number that has been tested at the required Fibre Channel line rate.
The optical engine uses an 850 nm VCSEL transmitter and a PIN photodiode receiver. The cable contains OM3- or OM4-grade multimode fiber, depending on the selected configuration.
Maximum available length is up to 70 meters with OM3-grade multimode fiber and up to 100 meters with OM4-grade multimode fiber. Actual supported distance depends on the cable configuration, host platform, coolant environment, operating temperature, and required link margin.
The standard operating module case-temperature range is 0°C to 70°C. The qualified coolant-temperature range depends on the selected dielectric fluid and should be confirmed for each project.
Power consumption is less than 1 watt per cable end for standard configurations. Exact typical and maximum power values should be confirmed in the relevant product datasheet.
Digital diagnostic monitoring is supported. Available parameters may include module temperature, supply voltage, transmitter bias current, transmit optical power, and receive optical power, depending on the selected configuration.
Applicable interface and management references may include IEEE 802.3by, SFF-8402, SFF-8418, SFF-8419, SFF-8432, and SFF-8472.
Regulatory compliance may include CE, FCC, and RoHS, subject to the applicable product declarations and test reports. The products are manufactured under an ISO 9001-certified quality management system.
Standard cable lengths include 1 m, 3 m, 5 m, 7 m, 10 m, 15 m, 20 m, 25 m, 50 m, and 100 m.
Immersion AOC vs. Extender vs. DAC: Choose the Right 25G Interconnect
Not every link inside an immersion cooling tank requires the same interconnect. The right choice depends on transmission distance, cable-routing space, power budget, cost, bend radius, and whether the active optical components will remain inside or outside the coolant.
Immersion Cooling AOC
An immersion cooling AOC is typically available in lengths from 1 meter to 100 meters. Both SFP28 ends and the optical cable may be continuously submerged, provided that the assembly has been qualified for the selected coolant.
Because it uses multimode optical fiber, the cable is light, thin, flexible, and easy to route in dense tanks. It is immune to electromagnetic interference and typically consumes less than 1 watt per end.
An immersion AOC is best suited to longer links, high-density racks, space-constrained cable routing, and applications that require electrical isolation and EMI immunity.
Immersion Cooling Extender
An immersion extender moves the standard optical transceiver or active component away from the wet-side switch or server port. The wet-side connector and extension cable may be submerged, while the standard transceiver remains above the coolant line or in a dry-side enclosure.
The supported distance depends on the extender design and the optical module used. Short extension lengths of approximately 1 to 3 meters are common, but the actual limit must be confirmed from the product specification.
An extender is useful when an operator wants to reuse standard SFP28 optics, keep active optical components outside the coolant, or simplify replacement and maintenance.
Immersion Cooling DAC
An immersion-rated DAC is generally used for short connections of approximately 1 to 7 meters. Both cable ends and the copper cable may be submerged if the assembly has been qualified for the selected coolant.
DACs contain no active optical electronics in the cable assembly and therefore have very low cable-level power consumption. However, they are heavier and less flexible than optical cables, especially at longer lengths. Copper cables are also more susceptible to electromagnetic interference than optical fiber, although properly shielded DAC assemblies normally provide good noise resistance.
An immersion DAC is best suited to short, cost-sensitive links where copper cable weight, bend radius, insertion loss, and routing space are acceptable.
Choose an immersion cooling AOC when you need longer reach, low cable weight, flexible routing, electrical isolation, and EMI immunity inside the tank.
Choose an immersion extender when you already use standard SFP28 optical modules and want to keep the active optics above the coolant line.
Choose an immersion cooling DAC when the link is short, cost is the primary consideration, and passive copper meets the system’s insertion-loss, bend-radius, and routing requirements.
Switch and Platform Compatibility
The most common question is simple: Will this cable work in my switch?
FiberMall 25G SFP28 immersion cooling AOCs can be coded for commonly deployed network platforms. Before shipment, each cable can be tested for EEPROM recognition, link establishment, and bidirectional traffic transmission on the specified target platform.
Where required, dedicated bit-error-rate testing can also be performed at 25.78125 Gb/s using defined test patterns and acceptance criteria.
Potentially supported platforms include:
• Selected Arista 7000-series switches with 25G-capable SFP28 ports
• Selected Cisco Nexus 9000 and Catalyst 9000 switches
• Selected Juniper QFX, EX, and MX platforms
• Selected NVIDIA Spectrum SN2000, SN3000, and SN4000 switches
• Selected H3C S12500, S6800, and S9850 platforms
• Selected HPE Aruba CX switching platforms
• Selected Ruijie RG-S6900 and RG-N18000 platforms
Compatibility should always be verified using the exact switch model, line card, port type, network operating-system version, FEC setting, port-speed configuration, and third-party transceiver policy.
A project-specific compatibility matrix can be provided with the datasheet.
Applications: AI, HPC, and High-Density Data Centers
25GbE remains widely used for server access, storage connectivity, management networks, control-plane connectivity, edge systems, and selected cost-sensitive compute environments.
In immersion-cooled systems, the interconnect must provide the required bandwidth while maintaining stable performance during continuous contact with dielectric coolant.
Common deployment scenarios include:
• AI infrastructure — Management, control-plane, storage-access, and auxiliary server links inside single-phase or two-phase immersion systems.
• HPC environments — Low-latency, electrically isolated optical links between selected submerged compute nodes, storage devices, and network switches.
• High-density data centers — Lightweight optical cabling for immersion-cooled racks where cable bulk, routing space, and airflow are no longer the only design constraints.
• Edge AI inference — Compact immersion-cooled enclosures in which conventional air cooling is insufficient or impractical.
• Storage and service networks — 25GbE connections for storage access, service nodes, monitoring systems, and infrastructure-management functions.
For modern high-performance GPU scale-out fabrics, higher-speed technologies such as 100G, 200G, 400G, or 800G are normally used for primary compute traffic. A 25G SFP28 immersion cooling AOC is therefore more commonly used for management, storage access, auxiliary connectivity, edge inference, and selected server-access applications.
Frequently Asked Questions
What is a 25G SFP28 immersion cooling AOC?
A 25G SFP28 immersion cooling AOC is a factory-terminated active optical cable with sealed SFP28 modules on both ends. It is designed to operate while submerged in a qualified dielectric coolant.
The assembly combines the optical transceivers and multimode fiber into one plug-and-play cable. It provides the convenience of a standard AOC while using cable materials, seals, adhesives, and optical components selected for immersion-cooling environments.
Can I use a standard 25G SFP28 AOC in an immersion cooling tank?
It is not recommended unless the cable manufacturer has specifically qualified the product for the exact coolant and operating conditions.
Standard AOCs generally use module seals, cable jackets, adhesives, and optical assemblies intended for air-cooled data centers. Prolonged coolant exposure may affect these materials, allow fluid ingress, contaminate the optical path, or reduce optical link margin.
Even when the cable initially establishes a link, long-term material degradation may lead to intermittent errors or premature failure.
Which dielectric fluids are compatible?
FiberMall immersion cooling AOCs can be supplied for selected PAO-based fluids, silicone oils, synthetic esters, mineral oils, and fluorinated dielectric fluids.
However, compatibility cannot be guaranteed solely according to the general fluid category. It must be confirmed using the exact coolant manufacturer, product name, chemical formulation, operating temperature, pressure conditions, and required exposure duration.
Compatibility with legacy 3M Novec or Fluorinert installations can be evaluated on request, subject to the availability and exact grade of the coolant.
Contact FiberMall before ordering if your tank uses a specialty fluid or a proprietary coolant formulation.
How far can a 25G SFP28 immersion cooling AOC reach?
Standard configurations are available up to 70 meters with OM3-grade multimode fiber and up to 100 meters with OM4-grade multimode fiber.
Actual supported reach depends on the cable design, host platform, coolant type, operating temperature, connector loss, optical power budget, and required system margin.
Custom cable lengths are available on request.
Are FiberMall immersion cooling AOCs compatible with Cisco, Arista, Juniper, and NVIDIA switches?
FiberMall can provide platform-specific coding for selected Cisco, Arista, Juniper, NVIDIA Networking, H3C, HPE Aruba, and Ruijie switches.
Compatibility must be confirmed using the exact switch model, port type, firmware or network operating-system version, FEC setting, and port configuration. A broad switch-family name alone is not sufficient to guarantee interoperability across every model.
Each cable can be tested for EEPROM recognition, link establishment, and traffic transmission on the specified platform before shipment.
When should I choose an immersion cooling AOC instead of an extender or DAC?
Choose an immersion cooling AOC when you need longer reach, low cable weight, flexible routing, EMI immunity, and electrical isolation inside the tank.
Choose an extender when you want to reuse standard SFP28 optical modules while keeping the active optics above the coolant line.
Choose an immersion cooling DAC when the link is short, cost is the main priority, and copper cable weight, bend radius, and insertion loss are acceptable.
Is a 25G SFP28 immersion cooling AOC backward compatible with 10G SFP+?
Some AOC configurations may support both 10.3125 Gb/s and 25.78125 Gb/s operation, but this is not guaranteed for every product.
Successful 10G operation depends on the cable design, CDR configuration, EEPROM coding, switch ASIC, firmware, and whether the host port supports 10G operation with an SFP28 device.
The required data rate and host platform should be confirmed before ordering.
Does the product support Fibre Channel or InfiniBand?
The standard configuration is intended primarily for 25 Gigabit Ethernet.
InfiniBand EDR support may be available on separately qualified configurations because the lane rate can be similar to that of 25GbE. However, host compatibility, coding, control signals, and system requirements must still be verified.
Fibre Channel uses different line rates and protocol requirements. Fibre Channel support should therefore only be specified for a dedicated part number that has been tested for the required Fibre Channel generation.
Do you provide test reports?
Yes. Standard shipment documentation can include optical, electrical, and switch-interoperability test results.
Depending on the order quantity and project requirements, FiberMall can also provide:
• Lot-level quality reports
• Serialized unit-level test reports
• EEPROM coding records
• Link-establishment and traffic-test results
• Bit-error-rate test results
• Coolant-compatibility qualification reports
• Pre-immersion and post-immersion optical performance comparisons
• Project-specific reliability reports
The exact test scope, test duration, coolant type, operating temperature, and acceptance criteria should be agreed upon before production.
Can the cable be used in both single-phase and two-phase immersion cooling systems?
The cable may be used in either type of system only when the exact configuration has been qualified for the selected coolant and operating conditions.
Single-phase and two-phase fluids can have significantly different chemical, thermal, pressure, and material-compatibility requirements. A product qualified in one mineral-oil-based single-phase fluid should not automatically be assumed to be compatible with a fluorinated two-phase coolant.
Contact FiberMall with the coolant model, operating temperature, expected exposure time, and tank design so that the correct cable construction can be selected.
