| Variant | Wavelength | Fiber Type | Max Reach | Typical Launch Power |
|---|---|---|---|---|
| SR | 850nm | MMF (OM3/OM4) | 300m (OM3) / 400m (OM4) | -1 to -7.3 dBm |
| LR | 1310nm | SMF OS2 | 10km | -3 to 0.5 dBm |
| ER | 1550nm | SMF OS2 | 40km | 0 to 4 dBm |
| ZR | 1550nm | SMF OS2 | 80km | 0 to 5 dBm |
These are IEEE and MSA-defined reach specifications. Real-world performance depends on fiber quality, connector cleanliness, and splice losses — but the table above reflects the design intent for each variant.
SR runs at 850nm over multimode fiber. OM3 gets you to 300m; OM4 extends that to 400m. Those numbers cover ToR switching, row-to-row interconnects, and short building runs where multimode infrastructure is already in place.
SR modules use a VCSEL (vertical-cavity surface-emitting laser), which is inexpensive to manufacture — and that keeps the unit price down. SR is consistently the cheapest 10G SFP+ variant. If your link is under 300m and you have OM3 or OM4 cabling installed, SR is the right call.
One field note worth keeping in mind: 850nm VCSELs are sensitive to dirty connectors. Fiber end-face contamination is behind most SR link failures. Clean before you connect.
Typical use cases: Data center ToR to aggregation, intra-building server-to-switch links, campus lab environments with existing multimode plant.
LR moves to 1310nm on single-mode fiber (SMF OS2) with a 10km reach. The shift from multimode to single-mode is significant — SMF's much lower attenuation per kilometer is what allows LR to cover 25 times the distance of SR.
LR uses a Fabry-Perot or DFB (distributed feedback) laser. The optics are more complex than a VCSEL, which is reflected in the price. That said, LR remains one of the most commonly deployed 10G variants and is priced competitively across the market.
Building-to-building campus links, main data center to remote IDF runs, and metro aggregation rings under 10km all fall squarely in LR territory.
Typical use cases: Campus building-to-building interconnects, enterprise WAN handoffs, ISP aggregation rings within a metro area, data center to remote office links under 10km.
ER operates at 1550nm with a maximum reach of 40km over SMF. Covering that distance requires higher launch power than LR — typically 0 to 4 dBm versus LR's -3 to 0.5 dBm. That output comes from a more capable DFB laser and, in many implementations, an integrated booster stage.
The 1550nm wavelength sits in the low-loss window of standard SMF, which is why ER can reach four times the distance of LR without inline amplification in most deployments.
ER modules cost significantly more than LR. The laser technology is more complex, thermal management requirements are tighter, and the power budget demands tighter component tolerances throughout the optical path.
Typical use cases: Metro fiber rings, ISP backbone interconnects between central offices, enterprise dark fiber spans between campus sites 15 to 40km apart, telecom aggregation nodes.
ZR pushes to 80km at 1550nm. To get there, ZR modules use a cooled DFB laser — a thermoelectric cooler (TEC) holds the laser at a stable operating temperature, keeping the wavelength stable and output power consistent across the full 80km span.
That cooling mechanism is the main reason ZR is the most expensive 10G SFP+ variant. The TEC adds cost, power draw, and thermal design complexity. ZR modules consume noticeably more power per port than SR or LR, which matters when you're planning port density on high-density line cards.
At 80km, fiber plant quality becomes critical. Splices, connectors, and patch panel losses accumulate fast. A link that looks clean on paper at 79km can fail if the fiber plant carries above-average splice losses. Budget conservatively and run an OTDR trace before deploying ZR on any new span.
Typical use cases: ISP long-haul metro and regional links, telecom dark fiber spans between cities or remote facilities, enterprise connections to co-location facilities 40 to 80km away.
Buying ZR for a 2km campus link is a real budget problem. ZR modules can run three to five times the cost of LR and ten or more times the cost of SR. If your link is 2km, LR covers it with margin to spare — the extra spend on ZR buys you nothing except a cooled laser running well below its designed operating range.
The reverse problem is worse. An SR module on a 5km single-mode run simply won't work. 850nm over SMF produces modal noise and attenuation that prevents a stable link from forming. The module may not negotiate a signal at all.
Match the module to the actual measured fiber distance — not the distance you think the route might be, and not the longest link in the building.
Work through these questions in order:
1. What is the measured fiber distance?
2. What fiber type is installed?
SR only works on multimode (OM3/OM4). LR, ER, and ZR require single-mode OS2. If you have multimode fiber and need more than 400m, you're looking at a media converter, a fiber plant upgrade, or a different architecture.
3. What is your actual optical power budget?
Calculate the link loss: fiber attenuation + connector losses + splice losses + patch panel insertion loss. Compare that against the module's receive sensitivity and minimum launch power. ER and ZR have more budget to work with, but that margin disappears quickly on a dirty or aging fiber plant.
4. What is the port power consumption budget?
ZR draws more power per port than LR or SR. On a 48-port line card, the difference adds up. Verify your switch or router's per-port power allocation before deploying ZR at scale.
5. What is the platform compatibility requirement?
All four variants are available in versions compatible with Cisco, Juniper, Huawei, and Arista platforms. If your switch enforces vendor lock-in, confirm the module is coded for your specific platform — or verify compatibility through published test data before purchasing.
If your distance requirement exceeds 80km, ZR isn't the answer. That's where CWDM and DWDM SFP modules come in. DWDM SFP modules can reach 120km and beyond on a single wavelength; CWDM variants cover intermediate distances at lower cost per channel than DWDM.
HYTOPTODEVICE carries CWDM and DWDM variants at reach distances from 10km to 120km, with at least one DWDM SFP listed at 160km — covering the full range from standard metro deployments to long-haul regional links. The catalog spans 1.25G to 800G across every major form factor, so if your network includes both 10G SFP+ links and higher-speed 400G or 800G segments, you can source the full stack from one supplier.
All four 10G SFP+ variants — SR, LR, ER, and ZR — are stocked in versions compatible with Cisco, Juniper, Huawei, and Arista platforms, with compatibility test videos and datasheets published on-site to support pre-purchase validation.
Can I use a 10G SFP+ ZR module on a link shorter than 40km?
Technically yes, but it's wasteful. ZR modules are designed for 40 to 80km spans. Using one on a 5km link means paying a significant price premium for a cooled laser and high launch power you don't need. Use LR for links under 10km and ER for links between 10km and 40km.
Will a 10G SFP+ SR module work on single-mode fiber?
No. SR at 850nm is designed for multimode fiber. On single-mode fiber, the modal characteristics are incompatible and the link won't form reliably. If you have single-mode fiber, use LR, ER, or ZR depending on distance.
What's the difference between ER and ZR at 1550nm?
Both operate at 1550nm, but ZR uses a cooled DFB laser (TEC-controlled) to achieve the higher launch power and wavelength stability needed for 80km spans. ER typically uses an uncooled or less aggressively cooled DFB laser sufficient for 40km. ZR costs more and draws more power per port.
Do I need a special fiber type for ER and ZR?
Standard single-mode OS2 works for both. The key variable is fiber plant quality — connector cleanliness, splice losses, and total insertion loss all affect whether the link achieves its rated distance. Run an OTDR trace on any span over 20km before deploying ER or ZR.
Are third-party 10G SFP+ modules compatible with Cisco and Juniper switches?
Yes, provided the module is correctly programmed for the target platform. Third-party compatible modules in this category typically deliver 70 to 90 percent cost savings versus OEM modules. Verify compatibility through published test data or compatibility videos from the supplier before purchasing.
What happens if I mix SR and LR on the same link?
The link won't come up. Both ends of a fiber link must use the same wavelength and fiber type. SR at 850nm on one end and LR at 1310nm on the other are optically incompatible. Both transceivers must match in variant.
When should I consider CWDM or DWDM instead of ZR?
If your distance requirement exceeds 80km, or if you need to carry multiple 10G channels over a single fiber pair, CWDM and DWDM SFP modules are the right direction. DWDM SFP modules support distances well beyond 80km and enable wavelength-division multiplexing to multiply capacity on existing fiber infrastructure.
The right 10G SFP+ variant comes down to one thing: actual link distance. Measure it, account for fiber plant losses, and match the module to the number. SR for multimode short runs, LR for campus and metro under 10km, ER for 10 to 40km spans, ZR for 40 to 80km. If you need more reach or multiple wavelengths on one fiber pair, step up to CWDM or DWDM. For the full catalog across all four variants and beyond, visit hytoptodevice.com.
