You can upgrade a 1G fiber link to 2.5G without new cable — the change is at both endpoints. The AOM-4100 2.5G media converter ships now in four models, covering non-PoE links and PoE budgets to 90 W. Below: six deployments where a 1G link caps throughput, the DIP matrix that decides the rate, and the cost split against Cat6A plus 10G.
Key takeaways
- The 1G ceiling sits in the PHY and SFP pair at each end — OM3 pulled for gigabit carries 2.5G to 550 m.
- A Wi-Fi 6 AP puts 1.4–2.4 Gbps of radio behind a 940 Mbps port; Wi-Fi 7 radios reach 5.4 Gbps.
- Rate mode is SW2 and SW3; LFP is SW1, default OFF.
Ethernet 1G vs 2.5G: Where the Link Actually Bottlenecks
The fiber installed for gigabit is rarely the limiting part. OM3 pulled for 1000BASE-SX carries 2.5G to 550 m. The ceiling sits at both ends: the switch PHY and the SFP pair doing the conversion.
- Access points outrun their uplink. A 4×4 Wi-Fi 6 AP delivers 1.4–2.4 Gbps into a port that tops out near 940 Mbps; Wi-Fi 7 radios reach a 5.4 Gbps PHY rate.
- Cameras multiply. One 4K stream is nothing. Thirty of them, and the gigabit is full.
The symptom rarely reads as bandwidth. The NAS copy stalls near the end, or the video wall drops frames at shift change.
Take 18 ceiling APs on one campus. Client link rates read 1.9 Gbps, but every AP still crosses a 1G port that stops near 940 Mbps. A converter pair per link moves that ceiling to 2.3 Gbps. Put one pair on each floor closet instead and six APs share 2.3 Gbps — under 400 Mbps each, worse than what they have. The arithmetic only works per link.
Sizing several closets at once? Compare all four models side by side.
What a 2.5G Fiber Link Actually Requires
All four must hold at once, or the link comes up at 1G.
- A 2.5G PHY at both ends. The copper port is four-speed (10/100/1000/2500 Mbps), and the switch port, AP or NIC on the far side must also do 2.5G.
- Optics rated 2500BASE-X. This is where most upgrades stall. A module labeled 1000BASE-X has a 1.25 Gbps line rate, and no host setting changes it. A 2500BASE-X module carries 2.5G and falls back to 1000BASE-X in a 1G slot; the SFP MSA rate codes are what those labels encode.
- Fiber type and a live loss budget. OM3 reaches 550 m at 2.5G, OM2 reaches 300 m, single mode runs 10 to 120 km depending on the module. Count every patch panel and splice.
- 2.5G Ethernet cable on the copper side: Cat5e or Cat6, 100 m. Four pairs terminated, shielded RJ45, no marginal outlets. A run certified years ago at 1G may not certify at the higher rate.
The cable plant carries over: a strand already carrying 1G carries 2.5G, unless the loss budget is spent or the fiber is OM1 at long reach. So does the SFP slot, often with the module still in it — you can reuse 1G SFP modules at 2.5G when the label reads 2500BASE-X, because the same part runs at 1G in an old switch and 2.5G in a new one.
Where the modules are older than the switches, the optical transceiver modules are the cheapest item in the project — one pair per link, 850 nm multimode or 1310 nm single mode; multi-rate 2.5G SFP modules cover both rates off one part number. The conversion layer is commodity: fiber media converters at both ends, or one converter plus a 2.5G access port on the switch platform.
Six Deployments Where a 2.5G Fiber Link Pays Back
The link, not the device, is what breaks in all six. Every one is the same job: upgrade a 1G fiber link to 2.5G and leave the glass alone.
Wi-Fi 6/6E/7 AP Uplink: The 1G Port Is the Ceiling
The AP reports a 2.4 Gbps link rate; a laptop three meters away tests at 600–700 Mbps. The uplink is the narrowest point, and every client shares it.
Radio count sets the power budget, and the budget sets the model. An AP asking 802.3at (25–30 W) runs on the AOM-4100AT-30 — the PoE media converter for Wi-Fi 7 AP rollouts where the far closet has no PoE left. An AP needing 802.3bt goes to the AOM-4100BT-90. A 2.5G fiber uplink for Wi-Fi 7 AP deployments turns that 940 Mbps port into 2.3 Gbps.
4K/8K Camera Backhaul: How Many Channels Fit on One Link
The recorder timeline shows gaps at shift change, and the camera that dropped frames reports a healthy stream.
At 20 Mbps per 4K stream, a 1G link carries about 30 channels after overhead and a planning margin; the same strand at 2.5G carries about 80.
Cameras on their own 12 V supply need nothing from the converter, so the standard AOM-4100 is enough. Where the converter also powers the camera, a 2.5G fiber backhaul for IP cameras carries 30 W of 802.3at to a 4K dome or a PTZ.
NAS, Render and AI Workstations: Fiber to the Desk
Work the numbers on a 40 GB project copy. A gigabit path moves about 110 MB/s, so the folder takes six minutes. At 2.5G — about 280 MB/s — the same folder lands in two and a half minutes. Five editors doing that twice a day get over half an hour back, every day.
Model: a standard AOM-4100 at each end, on the OM3 already in the wall. That is 2.5G fiber to the desk with no new cabling.
Meeting Room AV Backbone: 4K + BYOD + Dante in Parallel
A room that passes commissioning fails in use: the presenter feed is clean until someone joins the wireless share, then the audio crackles and the far display drops sync for two seconds.
Three streams run in parallel — a 4K feed at 20 Mbps, a BYOD share at 20–40 Mbps, a 64-channel Dante flow near 100 Mbps. Add them up: 160 Mbps at peak, a sixth of a gigabit. Bandwidth was never the problem. Dante breaks first because it is latency-sensitive, and a room sharing its uplink with the floor gets the queue, not the headroom.
Model: one AOM-4100 in the room, one in the closet, single mode if the room sits in another building. Priority handling stays on the switch; the converter passes tags untouched. The gain is a link floor traffic cannot queue behind.
SMB and Creative Studios: 2.5G on Cat5e Instead of Cat6A
The Cat6A re-pull quote lists 24 drops, two floors and a weekend of downtime — for a studio whose peak demand is five workstations hitting one NAS.
Every 1G fiber link upgrade to 2.5G here is two decisions: what runs between floors, and what runs to the desk. Between floors the fiber exists. To the desk, 2.5G Ethernet cable is still Cat5e or Cat6 at 100 m; Cat6A is not required when the run is sound.
Model: AOM-4100 at each end. Certify the copper before quoting new copper: a run that passes at 1G usually passes at 2.5G; a marginal one will not.
Campus and Dormitory: 2.5G to the Building, No Second Trench
Consider a 200-room block at eight in the evening. Streaming stalls, and the building’s 1G uplink sits pinned near 98% while demand clears 4 Gbps. A second trench is not on the table — but two strands in the existing duct already are. Two 2.5G links on them carry about 4.6 Gbps, enough for that peak, and the access layer sorts the rooms between.
Model: AOM-4100 in each building’s MDF. Campus runs are single mode, so a 2.5G fiber to the building keeps the existing duct and patch panel — 20 km on SFP-S2513L-20, or a BiDi pair where one strand is free.
Speed Mode and LFP: The DIP Switch Decision Matrix
Four switches sit under a cutout on the front panel: SW1 sets link fault pass-through, SW2 and SW3 set the rate mode, SW4 is reserved. Check the LEDs first: 2.5G lit means the copper side linked at 2.5G, 1G lit means it fell back.
AOM-4100 Rate Mode: What SW2 and SW3 Select
SW2 | SW3 | Mode | Use when |
OFF | OFF | Auto: copper and fiber negotiate independently | Default; both ends known 2.5G-capable |
ON | OFF | Force 1G: both sides pinned to 1000 Mbps | One side is 1G-only, or the fiber budget is marginal while you fix it |
OFF | ON | Optical follows electrical: fiber rate tracks copper | Copper resolves 2.5G but the fiber side settles at 1G by itself |
ON | ON | Reserved | Do not set |
Why does the link come up at 1G when both ends support 2.5G?
Three causes, most common first: a 1000BASE-X-only module, which caps the link at 1.25 Gbps whatever the converter does; a copper peer that is a 1G port; or a fiber side that resolved before the copper side — the OFF-ON position fixes that. A 2.5G link stuck at 1G is usually a parts problem.
Why does the link flap between 1G and 2.5G?
Flapping means the link runs at the edge of its budget. The receiver needs more margin at 2.5G, so a run that was comfortable for years turns marginal when the rate doubles: a contaminated connector, a tight bend, one bad pair in a patch panel, a copper run near 100 m. Clean and re-test, or set SW2 SW3 to ON-OFF and pin 1G until it is fixed.
Should LFP be on or off in a 2.5G fiber link?
Off in most installs, on wherever the link sits in a redundancy scheme. LFP propagates a lost link from one port to the other, so each switch sees the failure instead of a port that still looks up. The mechanism lives in the media converter FAQ; the decision is here.
Set SW1 on when the link carries a redundant path that must fail over, or when a managed switch needs to see the far end disappear before it reroutes. Leave it off when ports are patched routinely — a move-add-change outage becomes a propagated outage — when converters are daisy-chained, or when the far device trains slower than the LFP timeout.
Powering the Far End: When the Converter Is the PSE
The far closet is the awkward one: a 1G access switch with no PoE budget left, a ceiling void where nobody wants mains.
A Wi-Fi 6/6E AP or a PTZ camera draws 25–30 W, which lands on 802.3at — the AOM-4100AT-30 as an End-span PSE, which also covers 802.3af devices at 15.4 W. A Wi-Fi 7 AP with a 6 GHz radio needs 802.3bt Type 3 at 60 W on four pairs; Type 4 reaches 90 W for an AP plus a downstream device, or a PoE AV endpoint.
On a 60 W or 90 W load, spreading current across all four pairs roughly halves the per-conductor current of a 2-pair design, holding voltage drop inside the device’s input window over 100 m of Cat5e. Cat5e is not the data-rate limit at 2.5G; power is.
BT-60 and BT-90 need DC54V for a full 100 m run at full load; at DC48V, plan for under 30 m.
2.5G Fiber vs Cat6A + 10G: Cost, Effort, Closet Impact
The 2.5G vs 10G cost comparison is not like-for-like: one is a rate change on cable you own, the other a cabling project with a switch refresh attached.
Dimension | 2.5G on existing fiber (AOM-4100) | 10G on new Cat6A |
Cable work | None — reuse OM3, OM2 or single mode | Pulls, containment, patch panels |
Reach at rate | 550 m on OM3; to 120 km single mode | 100 m on copper |
Optics per link | Two 2500BASE-X modules (SFP-M2585L-05, SFP-S2513L-20) | Two 10G SFP+ or 10GBASE-T PHYs |
Switch port | Any 2.5G access port, or 1G plus converter | 10G at both ends |
Power draw | Under 0.5 W standby; 4 W or less on the standard model | Port power sits on the switch |
Rack space | 14 converters in 2U via AOR-14 | Far fewer 10G ports in the same 2U |
Cable work is the largest element of any cabling budget, and this path sets it to zero. Swapping endpoints is a maintenance-window job; pulling Cat6A is a project with ceiling access requests. Rack footprint closes the case — an AOR-14 14-slot 2U chassis holds 14 fiber links in 2U.
A 2.5G SFP media converter is not a switch replacement: it changes the physical layer on one link and leaves VLANs and routing where they are. The arithmetic flips once a closet needs several 2.5G links behind one box, or one PoE budget has to feed multiple powered devices — that is a 2.5G PoE switch, not a converter pair per link. AOA has one in development (status note at the end of this page); it is not orderable yet. Go 10G instead when one link must carry more than 2.5G of aggregate, when the core is already 10G, or on a new build where cable goes in regardless — transceiver options at both rates come from the same line.
Availability, Models and What Ships
The AOM-4100 family is in production and available now:
- AOM-4100 — standard, DC 5–12 V with a 5 V/2 A adapter. AP uplinks where the AP has local power, desk links, cameras on their own supply.
- AOM-4100AT-30 — 802.3af/at at 15.4/30 W, End-span, 48 W adapter.
- AOM-4100BT-60 — 802.3bt Type 3 at 60 W, 4-pair, 90 W adapter.
- AOM-4100BT-90 — 802.3bt Type 4 at 90 W, 4-pair, 120 W adapter.
The three PoE models take DC 48–57 V.
Shared platform: 1 × 2.5G RJ45 plus 1 × SFP slot, four-speed auto-sensing at 10/100/1000/2500 Mbps, IEEE 802.3bz, 802.3ab and 802.3u on copper, 2500BASE-X optics with 1000BASE-X fallback, hot-swap SFP, MDI/MDI-X, 802.3az EEE. Housing 94 × 71 × 26 mm zinc-plated metal, IP30, passively cooled; desktop, TK10 wall bracket or AOR-14 rack. LEDs: PWR, FDX, 2.5G, 1G, FL/A, TL/A, PoE.
Certification: EN 62368-1; EN 55032/55035; FCC Part 15 Subpart B Class A; IEC 61000-3-2, -3-3, -4-2 to -4-6 and -4-11; IEC 60068-2-6, -2-27, -2-32; RoHS 2.0 (2011/65/EU); PPWR (EU) 2025/40. Every unit is aged and throughput-tested before it ships, MTBF is rated at 100,000 hours or better, and the warranty is 3 years.
Planning a multi-site rollout? Send the link list — closet count, fiber type, measured loss, device draw — and the team returns a model-by-model match with module part numbers. The AOM-4100 product page carries the full spec sheet.
In development, not yet shipping: a 2.5G PoE switch for closets that need several 2.5G links behind one box. No model numbers, port counts or availability dates are fixed yet, and nothing on this page should be quoted as a current product. Tell the team if it sits on your project’s critical path and you want the spec sheet when it lands.
FAQ
Q: Can I upgrade a 1G fiber link to 2.5G without pulling new cable? A: In most buildings, yes. The fiber does not set the rate; the PHYs and the SFP pair do. If a strand already carries 1G, replacing both endpoints with 2.5G converters and 2500BASE-X modules usually delivers 2.5G on the same glass. Budget for loss first: OM3 reaches 550 m, OM2 reaches 300 m.
Q: Do I need new SFP modules for 2.5G? A: Sometimes. A module rated 1000BASE-X only has a 1.25 Gbps line rate and caps the link at 1G regardless of the converter. A 2500BASE-X module runs at 2.5G and falls back to 1G in an older slot. Read the part number on the module already installed.
Q: Will the converter still work on a 1G switch port? A: Yes. The copper port is four-speed and auto-negotiates, so it links at 1G with a 1G switch and passes traffic normally, with no configuration change. 2.5G arrives later when that access port is upgraded, without touching the cable or the converter.
Q: How much PoE power can reach a device across the fiber link? A: Up to 90 W at the PSE end with the BT-90 in 4-pair mode. Power is injected on the copper side only; the fiber carries data. On a 100 m Cat5e run a 90 W load needs a DC54V supply to stay within the device’s input window.
Author Bio
Written by the AOA Technology Engineering Team — the engineers who run the link-negotiation and PoE load tests behind these figures. AOA Technology has built fiber optic and industrial networking products in-house since 2008.
