Labels & colour codes: reading a module without a reader

Before a module is plugged into anything, its label and the colour of its latch already say what it is — if you know the code. This page decodes the printed label (which fields exist, what they mean, which EEPROM bytes they should match), the de facto colour codes of bail latches and pull tabs, fibre jacket and connector boot colours, and the regulatory marks. It is the bench-side counterpart of the memory map: what the sticker claims versus what the EEPROM says.

Anatomy of a module label

Rule: label and EEPROM must agree on vendor, PN, SN, date, λ and reach. A mismatch is either a recoded module (legitimate or not) or a counterfeit (Failures & counterfeits).

Bail latch and pull-tab colours

There is no MSA for latch colours, but the industry converged on a code for SFP-class modules; QSFP and 400G+ tabs are less consistent.

CWDM SFP latches follow a channel colour scheme that most vendors share for the upper band:

Lower-band channels (1270–1450 nm) use vendor-specific colours. DWDM modules are not colour coded by channel — the channel number and wavelength are printed on the label (Wavelength bands).

QSFP/QSFP-DD/OSFP pull tabs: beige, grey or black tabs mostly mean 850 nm SR4/SR8; blue often LR4/DR4; but many vendors use one colour for the whole line and rely on the label. DAC pull tabs are usually black with a length sticker; AOC tabs are often aqua like OM3/OM4 jackets.

Fibre and connector colours

Regulatory and safety marks

Reading a label in 20 seconds

1. Vendor and PN → which family and grade (Part numbering).
2. λ and reach → single- or multi-mode, budget class (Reach tables).
3. Latch colour agrees with λ? If not, suspect a re-latched or relabelled module.
4. Temperature grade printed? If not, assume commercial.
5. Date code recent and SN format plausible for the vendor?
6. Then read the EEPROM and compare every field (Memory map).

In CodingBox

The Check screen shows vendor, PN, SN, date, wavelength, lengths and compliance codes in one view — hold the module next to the screen and compare with the label. The code database keeps photographs and notes per PN, so a label variant seen once is recognised the next time.