Complete FAQ guide to optical transceivers: SFP vs QSFP, SR/DR/FR/LR reach explained, 400G vs 800G comparison, multi-vendor compatibility testing, AOC vs transceiver+fiber, and lead times for procurement.
1. What is the difference between 400G and 800G optical modules?
| 400G | 800G | |
|---|---|---|
| Data Rate | 400 Gbps | 800 Gbps |
| Primary Use | Current-gen data center, metro networks | Next-gen data center, AI/ML clusters |
| Power per Port | ~10–14W | ~14–18W |
| Maturity | Mature, widely deployed | Early deployment, growing supply |
| Cost Premium | Baseline | 2–3× higher than 400G |
When to choose 400G: You're deploying now or in the next 12 months. Volume pricing is competitive, supply is stable.
When to choose 800G: You're building for AI/ML clusters or planning infrastructure that needs to scale past 2027. Consider if your switch silicon supports 800G ports.
2. What form factors are available?
| Form Factor | Max Speed | Connector | Typical Use |
|---|---|---|---|
| SFP28 | 25G | LC duplex | Server access, enterprise |
| QSFP28 | 100G | LC duplex / MPO | Data center interconnect |
| QSFP-DD | 400G / 800G | LC duplex / MPO / CS | High-density data center |
| OSFP | 400G / 800G | LC duplex / MPO / CS | AI/ML clusters, hyperscale |
| CFP2 | 100G/200G | LC duplex | Telecom, long-haul |
| SFP-DD | 100G | LC duplex | Server-to-ToR |
Most common today: QSFP28 (100G) and QSFP-DD (400G). OSFP is gaining traction for 800G.
Key compatibility check: Make sure your switch/router port cage accepts the form factor. QSFP-DD ports are backward-compatible with QSFP28 modules. OSFP ports generally are not.
3. What do SR, DR, FR, and LR mean?
| Code | Full Name | Reach | Fiber Type | Typical λ |
|---|---|---|---|---|
| SR4/SR8 | Short Reach | 100m | OM4 MMF | 850nm |
| DR4/DR8 | Datacenter Reach | 500m | SMF | 1310nm |
| FR4 | 400G (4λ) | 2km | SMF | CWDM |
| LR4 | Long Reach | 10km | SMF | LAN-WDM |
Quick selection:
In-rack / same row: SR (multimode fiber, cheaper optics)
Across data hall: DR or FR (single-mode fiber)
Between buildings/campuses: LR (10km single-mode)
SR modules cost less than DR/FR/LR but require multimode fiber infrastructure. If your facility is single-mode fiber only, go with DR or FR.
4. Are third-party / compatible optical modules reliable?
Yes, from quality vendors that perform full compatibility testing.
Concerns about "locking" are mostly a historical issue. Modern compatible modules from reputable suppliers:
Are tested on the target switch platform (Cisco, Juniper, Arista, etc.)
Meet or exceed the same MSA (Multi-Source Agreement) standards as OEM modules
Cost 40–70% less than OEM-branded equivalents
Come with 3–5 year warranty from quality suppliers
What to verify before buying compatible modules:
Compatibility report for your specific switch model and OS version
MSA compliance documentation
Warranty terms and RMA process
Whether your switch vendor's support policy covers third-party optics
5. What is the difference between AOC and optical transceiver + fiber?
| AOC (Active Optical Cable) | Transceiver + Separate Fiber | |
|---|---|---|
| Connectors | Fixed, factory-terminated | Plug-and-play, interchangeable |
| Distance | Typically 1–30m | Up to 10km+ |
| Installation | Plug one cable | Connect transceiver + attach fiber |
| Flexibility | Low — fixed length | High — swap transceivers or re-patch |
| Cost at Scale | Lower for short, high-density | Lower for longer distances |
| Cable Management | Cleaner for ToR-to-server | More flexible for structured cabling |
Rule of thumb: AOC for server-to-ToR (≤30m, fixed topology). Transceivers + fiber for structured cabling, longer distances, and anything that might need re-patching.
6. How do I ensure compatibility with my network equipment?
Before ordering, provide us with:
Switch/Router brand and model (e.g., "Cisco Nexus 93180YC-FX")
Switch OS version (e.g., "NX-OS 10.2(5)")
Required speed and reach (e.g., "400G FR4, 2km")
Any known vendor-specific requirements
We provide:
Pre-shipment compatibility test report
MSA compliance documentation
Configuration guidance if needed
We recommend ordering 2–4 modules for initial qualification before committing to volume.
7. What lead times should I expect?
| Module Type | Typical Lead Time | Notes |
|---|---|---|
| 100G SR4/LR4 | 1–2 weeks | Widely available |
| 400G FR4/DR4 | 2–4 weeks | Growing demand, expanding supply |
| 400G SR8 | 1–2 weeks | Mature product |
| 800G (all types) | 4–8 weeks | Early market, limited supply |
| AOC Cables | 1–3 weeks | Custom lengths add time |
Contact us for current availability on specific models.
8. Can ADD Components help with optical module selection?
Yes. We supply Finisar (Coherent), Lumentum, and compatible-brand optical modules across all major form factors and reach specifications. Our team can:
Recommend the right module for your switch platform and distance requirements
Provide compatibility testing documentation
Source hard-to-find modules when authorized channels have long lead times
Supply modules + FPGA + support ICs as a consolidated order
Contact us with your network equipment details for a recommendation and quote.
Last updated on July 06, 2026