Cisco SF-SM31020D-GP
Cisco · SFP transceiver, 1000BASE-LX · SF-SM31020D-GP
what it is
A 1000BASE-LX transceiver (Cisco) in the SFP form factor, part number SF-SM31020D-GP. Wavelength from the transceiver memory: 1310 nm. Production year stored in memory: 2011. Revisions seen in the examined units: 11.0. Units examined: 1.
what we read from it
The transceiver memory declares optical diagnostics (DOM) with external calibration — the variant in which the switch itself converts raw readings using coefficients stored in the transceiver. In the examined unit, however, the measurement page was empty: all zeros, including where the alarm thresholds should be, and the WS-C2960CX-8PC-L switch did not list this transceiver in its diagnostics table. So diagnostics are declared in memory, but no measurements were read from it.
Whether they can be read in another switch, we have not checked yet.
what the transceiver memory declares
Transceiver memory read directly from a Cisco switch (show idprom, SFF-8472 section) — 1 unit. Each item gives the memory byte and value it comes from; we do not show serial numbers, exact dates or the vendor-reserved area.
- Module type: SFP/SFP+ (byte 0 = 0x03).
- Connector: LC (byte 2 = 0x07).
- Standard (compliance code): 1000BASE-LX (bytes 3, 6 = 0x00, 0x02).
- Also Fibre Channel: yes (bytes 7, 10 = 0x12, 0x01).
- Nominal rate: 1300 MBd (byte 12 = 0x0D).
- Reach per fiber type: single-mode 10 km, OM2 550 m, OM1 550 m (bytes 14-19 = 0x0A 0x64 0x37 0x37 0x00 0x00).
- Wavelength: 1310 nm (bytes 60-61 = 0x05 0x1E).
- Hardware signals: loss of signal (RX_LOS), transmitter fault (TX_FAULT), transmitter disable (TX_DISABLE) (byte 65 = 0x1A).
- Optical diagnostics (DDM): declared, external calibration (byte 92 = 0x58).
- Extended options: alarm flags set by the transceiver (byte 93 = 0x80).
- SFF-8472 diagnostics revision: 9.3 (byte 94 = 0x01).
- Chip vendor identifier (OUI): filled (bytes 37-39).
- Memory checksums: valid (bytes 63 and 95).
- Vendor-reserved area: present (bytes 96-127).
- Vendor alarm thresholds: not shown — external calibration, and the values in memory need conversion with constants stored in the transceiver.
- Production year stored in memory: 2011.
A declaration in memory is not the same as a reading: none of the switches examined showed diagnostic measurements (WS-C2960CX-8PC-L).
how we checked
The result depends on what the transceiver was read with — the same switch model in a different installation can show different data. That is why each reading is recorded separately:
- Cisco Catalyst 2960CX-8PC-L (WS-C2960CX-8PC-L), firmware
15.2(7)E14— transceiver memory and diagnostics table read from the console, 2026-10-19: diagnostics not shown (1 unit). Visible data: loss of signal indication (RX_LOS), transmitter fault indication (TX_FAULT), transmitter disable (TX_DISABLE), manufacturing date, wavelength, reach per fiber type, diagnostics standard revision, standard (compliance code), chip vendor identifier, memory checksums, identity (manufacturer, part number, serial number, revision). Cable test: not tested.
The same transceiver in other switches and a comparison with other models: what each device shows.
what we cannot read
- Measurements and alarm thresholds — in the examined unit the measurement page contained only zeros, and the switch did not show it.
parameters the transceiver returns
The list shows WHAT the device exposes — including parameters we do not use ourselves. There are no values here at all: it is a catalog of capabilities, not a reading from anyone's network. It is not a closed list either — explanation below the table.
14 parameters
| parameter | type |
|---|---|
data_produkcji | date |
dlugosc_fali_nm | number (nm) |
numer_czesci | text — part number (PN) |
numer_seryjny | text |
oui_producenta | text — chip vendor identifier |
producent | text — vendor name from transceiver memory |
rewizja | text |
rewizja_sff8472 | text — diagnostics standard revision |
sumy_kontrolne | boolean — transceiver memory validity |
usterka_nadajnika_tx_fault | boolean |
utrata_swiatla_rx_los | boolean |
wylaczenie_nadajnika_tx_disable | boolean |
zasiegi_wlokien | numbers (m / km) for OM1–OM3 and single-mode fiber |
zgodnosc | text — standard (e.g. 1000BASE-LX) |
This is not a closed list. It comes from reading a unit we had access to — it shows what we managed to retrieve, not everything the device can return. A different firmware version, hardware variant or reading path can expose fields that are not here. If you are interested in a specific unit and a specific value — please ask; there is a good chance it can be obtained, even if you do not see it below.
List source: reading of 1 working unit (as of 2026-10-19). The list is the sum of what we observed — more units reveal more parameters, so numbers for different models are not directly comparable.