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Optical Transceiver Selection Guide for ISPs
A concise, field‑tested guide to choosing SFP/SFP+/QSFP28 optics for small and regional ISP networks. Start from the link type--access, aggregation or edge--then narrow down by speed, distance, fiber type and platform compatibility.
Scope: 1G / 10G / 100G optics for ISP access, aggregation and broadband edge. For data center fabrics, see the Data Center Solutions page.
How to use this guide
Start from the link, then narrow down
For ISP networks, the easiest way to pick optics is to treat each link as a small checklist: where it sits in the network, what distance it needs to cover, and which devices are at each end.
Step 1 - Identify the layer
Decide whether the link is in access (FTTx cabinet / ONU), aggregation / metro ring, or broadband edge / core. This narrows the typical speed and reach immediately.
Step 2 - Measure speed & distance
Confirm port speed (1G / 10G / 100G) and approximate fiber distance (0.5-3 km, 10 km, 40-80 km). This points you to SR/LR/ER/ZR or DWDM options.
Step 3 - Check fiber & platform
Note fiber type (SM/MM), connector (LC/SC), and the exact device models on both ends. Finally, pick optics that are coded and validated for those platforms.
Recommended optics by layer
Access, aggregation and edge: what ISPs actually use
The tables below capture a "80%" view of what works well in most small and regional ISP networks. You can treat them as a starting configuration and adjust around special cases.
1. Access & FTTx uplinks
Links from OLTs and access switches in cabinets or small POPs back to aggregation or BNG sites.
| Scenario | Typical distance | Recommended optics | Notes |
|---|---|---|---|
| OLT / access switch in same site | 0.5-3 km | 1G SFP SX/LX or 10G SFP+ SR/LR | Use SX on multimode, LX/LR on single‑mode. Favor 10G SFP+ where you expect growth. |
| Cabinet / micro‑POP back to POP | 3-10 km | 10G SFP+ LR | LR covers most town‑scale access links on single‑mode fiber with good margin. |
| Single‑fiber FTTx or fiber‑scarce routes | 0.5-20 km | 1G / 10G BiDi SFP/SFP+ | Always order matched wavelength pairs (e.g. 1310↔1550). Check compatibility for both devices. |
2. Aggregation & metro rings
Links between aggregation routers/switches and between regional POPs.
| Scenario | Typical distance | Recommended optics | Notes |
|---|---|---|---|
| 10G ring or hub‑and‑spoke | 10-40 km | 10G SFP+ ER | ER is a good default for most single‑channel metro links within one region. |
| Long single‑channel spans | 40-80 km | 10G SFP+ ZR | Check optical budget carefully (fiber loss, splices, patch panels). Consider amplifiers if margin is tight. |
| Fiber‑scarce metro / regional | 10-80 km | CWDM / DWDM 10G SFP+ with passive mux/demux | Plan channels and route diversity first, then assign optics. Keep spare channels for future growth. |
3. Broadband edge & core
Links around BNG/BRAS sites, core routers and peering / upstream connections.
| Scenario | Typical distance | Recommended optics | Notes |
|---|---|---|---|
| BNG / edge router to core | 1-10 km | 40G QSFP+ LR4 or 100G QSFP28 LR4 | 100G LR4 is a good long‑term default where budgets allow. Use 40G LR4 when devices or traffic levels require it. |
| Core to IX / upstream provider | 1-40 km | 10G SFP+ LR / ER or 100G QSFP28 LR4 | Many IX links still run at 10G; plan migration paths to 100G where traffic growth is clear. |
| Longer peering / regional core | 40-80 km | 10G ZR, 100G LR4 with DWDM, or 100G ZR/ZR+ | Choice depends on existing DWDM gear and future plans. ZR/ZR+ is attractive where you want fewer boxes. |
Quick checklist
Before you place an order, confirm these four items
1. Device & port details
- • Exact device models and software versions on both ends.
- • Port type (SFP / SFP+ / QSFP+ / QSFP28) and licensed speed.
- • Any vendor restrictions on third‑party optics.
2. Fiber & distance
- • Fiber type (single‑mode or multimode) and connector (LC/SC).
- • Approximate distance and any known splice / patch points.
- • Whether you have spare strands or need BiDi / WDM.
3. Redundancy & future growth
- • Is this link part of a redundant path (LAG/ECMP, ring)?
- • Expected traffic growth in the next 2-3 years.
- • Whether 10G today should be 100G‑ready in design.
4. Compatibility & coding
- • Required vendor coding (Cisco/Juniper/Huawei, etc.).
- • Any mixed‑vendor optics concerns on the same path.
- • Need for DDM/DOM monitoring or special alarms.
FAQ
Common ISP questions about optics
Can I mix OEM and compatible optics in the same network?
Yes--when modules are coded and tested for your platforms, and link budgets are respected, mixing is common practice. We generally avoid mixing very different reach types (for example SR with ZR) on short paths, and flag any edge cases during design.
How many spare optics should a small ISP keep?
As a starting point, many ISPs keep 1-2 spares per critical SKU per region (for example, your most common 10G SFP+ LR and 100G LR4). Once we see your network map, we can suggest a compact spare plan.
What if I only know the devices and sites, not exact distances?
That's fine--send us the device list and rough geography (same building, same town, regional), and we'll propose optics with comfortable margin. You can refine distances before final ordering.
Want a selection guide tailored to your ISP?
Share a simple diagram or spreadsheet of your current links, and we'll return a draft optics plan plus a short PDF selection guide specific to your network.