OPTIC SFP-S-31DLC20D
OPTIC · SFP transceiver, 1000BASE-LX · SFP-S-31DLC20D
what it is
A 1000BASE-LX transceiver (OPTIC) in the SFP form factor, part number SFP-S-31DLC20D. Works over two single-mode (SM) fibers (duplex), 1310 nm. Reach per manufacturer: 20 km. These properties follow from the part number and the typical specification of this class — there is no manufacturer datasheet. Units examined: 2.
what we read from it
The transceiver has optical diagnostics (DOM): the switch reads temperature, supply voltage, laser bias current, transmit power and receive power from it. This makes an aging laser or a dirty connector visible before the link starts losing data.
Reading confirmed in switches: UniFi Switch Aggregation Pro and UniFi Switch 16 PoE (code USL16P).
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:
- UniFi Switch 16 PoE (USL16P), firmware
7.4.1.16850— transceiver fields in the UniFi controller, 2026-10-17: diagnostics read (1 unit). Visible data: temperature, supply voltage, laser bias current, transmit power, receive power, transmitter fault indication (TX_FAULT), standard (compliance code), identity (manufacturer, part number, serial number, revision). Cable test (production link at the customer site): link comes up 1 of 1; diagnostics suspicious 1 of 1; alarm after unplugging not checked — we do not unplug at the customer site. - UniFi Switch Aggregation Pro, firmware
7.4.1.16850— transceiver fields in the UniFi controller, 2026-10-17: diagnostics read (1 unit). Visible data: temperature, supply voltage, laser bias current, transmit power, receive power, transmitter fault indication (TX_FAULT), standard (compliance code), identity (manufacturer, part number, serial number, revision). Cable test (production link at the customer site): link comes up 1 of 1; diagnostics consistent with the other end of the link 1 of 1; alarm after unplugging not checked — we do not unplug at the customer site.
The same transceiver in other switches and a comparison with other models: what each device shows.
what we cannot read
- Manufacturer alarm thresholds — the switches that read it do not pass them on. The thresholds are in the transceiver memory and are shown e.g. by a Cisco switch.
- Manufacturing date and wavelength — not visible when read through the controller; they are in the transceiver memory.
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.
11 parameters
| parameter | type |
|---|---|
moc_nadawana | number (dBm) |
moc_odbierana | number (dBm) |
napiecie_zasilania | number (V) |
numer_czesci | text — part number (PN) |
numer_seryjny | text |
prad_lasera | number (mA) |
producent | text — vendor name from transceiver memory |
rewizja | text |
temperatura | number (°C) |
usterka_nadajnika_tx_fault | boolean |
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 2 working units (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.