Optical transceivers & cables

Transceivers & form factors

• What is an optical transceiver?
• Form factors: overview & comparison
• GBIC
• SFP
• SFP+
• SFP28
• SFP56
• SFP-DD
• XFP
• QSFP
• QSFP+
• QSFP28
• QSFP56
• QSFP112
• QSFP-DD
• OSFP
• OSFP224 (OSFP 224G)
• OSFP-XD
• Write-protection types & programming

Inside the module: lasers & receivers

• The optical front end: TOSA, ROSA, BOSA
• Laser types: VCSEL, FP, DFB, EML, tunable, SiPh
• Receivers: PIN, APD, TIA & coherent detection
• Optical packaging: TO-cans, boxes, lenses, isolators
• WDM inside the module: filters, AWGs, BiDi, wavelength control
• Module electronics: driver, TIA/LA, DSP, controller, power
• CDR — clock and data recovery
• NRZ, PAM4 and the DSP: retimers, gearboxes, LPO, coherent
• The controller and its firmware: DDM, APC, memory, protection
• Lasers by form factor & data rate
• Chip-on-board (COB) packaging
• How modules are made and tested
• Inside DAC, AOC and AEC cables

Specifications & standards

• MSA & standards overview
• MSA specification catalog (SFF/INF)
• SFF-8472 — SFP diagnostics
• SFF-8472 A0h register map
• SFF-8472 A2h register map
• SFF-8636 — QSFP management
• SFF-8636 lower page 00h register map
• SFF-8636 upper pages register map (00h, 03h)
• SFF-8024 — code tables
• CMIS — common management
• CMIS lower page register map
• CMIS upper pages register map (00h, 01h, 02h)
• CMIS lane pages register map (10h, 11h, VDM, CDB)
• MIS — SFP-DD management
• Two-wire interface: addresses, pages, banks & timing
• Compliance codes: bytes 3–10, 36 & extended tables
• Vendor fields: name, OUI, PN, SN, date code
• Checksums: CC_BASE, CC_EXT, CC_DMI, CMIS pages
• Specification revisions & version bytes
• What the host does: discovery, validation, bring-up
• SFP family hardware specs (INF-8074, SFF-8431…)
• QSFP family hardware specs (SFF-8436, SFF-8665…)
• INF-8077i — XFP management (+ X2, XENPAK)
• INF-8077i XFP register map
• Tunable DWDM memory maps: SFF-8690, SFF-TA-1004
• Rate & application selection: SFF-8079, SFF-8089
• Optical interface MSAs: CWDM4, PSM4, 100G Lambda, ZR/ZR+

DDM/DOM diagnostics

• DDM basics
• DDM parameters & units
• Typical DDM values by module type
• Thresholds, alarms & flags
• Internal & external calibration
• Accuracy and limits of DDM
• Rx power and the link budget
• Tx bias current and laser ageing
• Temperature and supply voltage
• Per-lane diagnostics: QSFP & CMIS
• VDM and FEC metrics: PAM4 links
• Monitoring DDM in production
• Reading DDM with tools: CLI, ethtool, SNMP, OpenConfig

Common problems & solutions

• Problem map & diagnostic method
• Symptom index: where to start
• No link: the checklist
• Vendor lock & «unsupported transceiver»
• Third-party optics: reliability & economics
• DDM levels & thresholds in practice
• Link flapping, CRC & dirty connectors
• Physical-layer mismatches
• Speed, rate & mode problems
• Power classes, low-power & overheating
• DAC vs AOC vs transceivers
• Failures, overheating & counterfeits
• EEPROM recoding: passwords & mechanics
• EEPROM read & write errors on the programmer
• CMIS modules: QSFP-DD 400G/800G issues
• PON problems: ONU registration, LOS & levels

Reference

• Glossary
• Abbreviations A–Z
• Units & conversions
• Wavelength bands & channel plans
• Connectors & fibre types
• Reach tables: how far each optic goes on each fibre
• Power classes & typical consumption by module type
• Temperature grades: commercial, extended, industrial
• Labels & colour codes: reading a module without a reader
• Reading a transceiver datasheet
• EEPROM memory map quick reference
• Standards map: who publishes what
• Optics FAQ: short answers to common questions