The High-Speed Optical Module Knowledge Base
An independent engineering reference for optical transceivers and data center interconnect — selection guides, link-budget calculations, standards maps, and AI-cluster optics, from 155M SFP to 1.6T. Published by Canjin Technology. No sales, no inquiries: pure technical knowledge.
Latest articles
1.6T Transceivers in 2026: What 200G-per-Lane Actually Changes (Notes from the Spec Trail)
Short technical notes on the 1.6T transition: 200G PAM4 lane rate, OSFP-XD and QSFP-DD1600/OSFP-RHS form factors, thermal implications, and why 1.6T o
100G QSFP28 Selection Guide: SR4 vs LR4 vs CWDM4 vs DWDM4
A practical selection guide for 100G QSFP28 optics: SR4 vs PSM4 vs CWDM4 vs LR4 vs DWDM4 compared by wavelength plan, fiber type, reach, FEC assumptio
10G SFP+ vs 25G SFP28: Migration Planning and Compatibility Matrix
How 10G SFP+ and 25G SFP28 actually differ — line rate, FEC, media reach, DAC lengths — plus a module-in-port compatibility matrix and the migration p
400G/800G Link Budget and OSNR Calculation: Formulas, Worked Examples, and DDM Interpretation
A practical engineering walkthrough of optical link budget for 400G and 800G transceivers: insertion loss allocation, power budget formulas, OSNR esti
800G Transceiver Selection Guide: OSFP vs QSFP-DD800, DR8 vs 2×FR4, and Power Classes Explained
How to choose 800G optics in 2026: form factor decision (OSFP vs QSFP-DD800), PMD selection by reach (VR8/DR8/SR8/2×FR4), power classes and thermal pl
Optical Interconnect Design for AI Clusters: GPU Fabrics, Spine-Leaf vs Rail-Optimized, and When CPO/LPO Makes Sense
How AI/ML compute clusters reshape optical interconnect choices: east-west traffic patterns, rail-optimized vs spine-leaf topologies, 800G module plac
IEEE 802.3 for 400G and 800G Explained: Which Standard Governs Your Transceiver (802.3bs, 802.3cu, 802.3df, 802.3dj)
A practical map of the IEEE 802.3 Ethernet amendments behind 50G-per-lane optics: what 802.3bs, 802.3cd, 802.3cu, 802.3df and 802.3dj actually define,
OSNR Calculation for Coherent 400ZR Links: Step-by-Step Examples
How to compute OSNR for 400ZR coherent DCI links: the 0.1 nm reference, the per-span formula with the 58 dB constant, span stacking with 10·log10(N),
Browse by topic
Module Selection Guides
Transceiver selection by data rate (10G/25G/100G/400G/800G/1.6T), form factor (SFP+/SFP28/QSFP28/QSFP-DD/OSFP), wavelength, single-mode vs multi-mode, and compatibility.
Technical Calculations
Link budget, attenuation, OSNR, power budget, and dispersion formulas with worked examples and DDM parameter interpretation.
Troubleshooting
Step-by-step diagnosis for modules that fail to link, error counters, DDM alarms, compatibility faults, and hot-swap problems.
Standards & Specs
Plain-engineer explanations of IEEE 802.3, QSFP-DD MSA, OSFP MSA, and related optical interconnect specifications.
AI Datacenter Optics
Optical interconnect design for AI/ML clusters: GPU fabrics, spine-leaf topologies, co-packaged optics, and short-reach high-speed links.
Blog
Short technical notes, field test logs, industry updates, and hands-on evaluations.