When discussing optical module compatibility, it has almost become a mantra to just write a code, but few people explain clearly what is written in the code and what the switch is reading. This article breaks down the writing code from the EEPROM structural level.
Identification and diagnostics are stored in the same chip
The SFP module provides a storage area to the switch through a two-wire interface, with a common capacity of 256 bytes, divided into two pages, A0 and A2: Page A0 stores static identification such as manufacturer name, model, OUI, wavelength, transmission distance, and upper temperature limit; Page A2 stores serial numbers, diagnostic calibration coefficients, and alarm thresholds for each monitoring item. It is these bytes that are read when the module is hot-plugged or when the switch is powered on.
Diagnostic capabilities are also supported by this chip: DDM readings are converted into receive and receive luminous power and temperature through the calibration area on page A2. If you only change the A0 page when writing codes and miss the alarm area, the recognition will be normal but the readings will continue to be false alarms.
Whitelists usually check these sets of fields
- Vendor Name and Vendor OUI: Most brands use this to determine whether the module is produced by themselves;
- Part Number and Revision Number: Some models require exact matching to the version field;
- Reserved area checksum: Some brands store checksums in the extended area, and simple copying of fields will result in miscalculations;
- Power and Temperature Caps: Determines whether the port accepts DDM readings for this module and allows full speed operation.
Writing code is a common process in the industry and does not change the module itself.
After writing the corresponding logo and threshold content according to the target brand, the module's optoelectronic devices, drive circuits and factory calibration data will not change. This is why the same module can be rewritten repeatedly to adapt to switches of different brands. likeSFP Gigabit single mode dual fiber 10KM optical moduleFor this type of standard packaging products, all EB-LINK series support free coding customization according to brands such as Cisco, Huawei, H3C, ZTE, Ruijie, etc., and will be read back and verified one by one before shipment.
Once you see the chip structure clearly, the compatibility issue will no longer be a mystery: first check the fields being verified, and then talk about the optical power and wavelength, and the troubleshooting idea will be much clearer. If you need to check the code corresponding to your model, please call 0755-83179002.