MikroTik SFP Modules Explained: How to Choose the Right Transceiver

MikroTik’s optical modules are among the best-value transceivers in networking — but the naming (S+, XS+, XQ+, DDQ+…) trips up a lot of buyers. This guide decodes the lineup and walks you through choosing the right SFP, SFP+, SFP28, QSFP28 or QSFP-DD module for your MikroTik switch or router, whether you’re lighting up a single gigabit uplink or a 400G data-center spine.

1. Start with the port, not the module

Every transceiver has a form factor, and it must physically and electrically match the cage on your MikroTik device. The form factor also caps the speed:

Check the datasheet for your exact model — a port labelled “SFP+” runs 10G and 1G, but not 25G. When in doubt, look up the device in the MikroTik catalog and confirm the per-port speeds.

2. Decode the MikroTik part number

Once you know the form factor, the rest of the part number tells you the reach and fiber type. Take S+31DLC10D as an example:

• S+ — SFP+ (10G) form factor
• 31 — wavelength family (1310 nm, single-mode)
• D — dual (duplex LC) fiber
• LC — LC connector
• 10 — 10 km reach
• D — DDM/DOM digital diagnostics

So S+31DLC10D is a 10G, single-mode, duplex-LC module good for 10 km. Compare that to S+85DLC03D: 10G, 850 nm (multi-mode), duplex LC, 300 m. The “85” vs “31” is the quickest tell for multi-mode vs single-mode.

3. Single-mode or multi-mode?

This is the decision that most often gets fixed in the field — so get it right up front. It’s dictated by the fiber already in the ground and the distance:

• Multi-mode (850 nm, “85” modules): cheaper optics, shorter reach. Good for in-rack, in-room and short in-building runs — up to ~300 m at 10G, ~550 m at 1G. Fiber is usually aqua-jacketed (OM3/OM4).
• Single-mode (1310/1550 nm, “31”/“55” modules): reaches 10, 20, 40, even 80 km. The choice for building-to-building, tower and metro links. Fiber is yellow-jacketed (OS2).

Both ends of a link must use the same wavelength and fiber type. You can’t pair a multi-mode module with single-mode fiber, or a 1310 nm module with a 1550 nm one.

4. When fiber is scarce: BiDi and CWDM

Running out of fiber strands is common. Two module types stretch what you have:

• BiDi (single-strand): transmit and receive on one fiber using two wavelengths, paired A/B. MikroTik ships these as matched pairs like S-4554LC80D (an S-45LC80D + S-54LC80D set).
• CWDM: assign each link its own colour (1470–1610 nm) and combine many links onto one fiber pair through a CWDM mux. MikroTik’s ladder runs S-C47DLC40D through S-C57DLC40D at 1.25G/40 km, plus the 10G S+C61DLC10D. This is how WISPs and campuses multiply capacity without trenching new fiber.

5. Copper without the fiber: DAC and RJ45 modules

Not every link needs glass:

• Direct Attach Cables (DAC / twinax): a fixed copper cable with the modules molded on both ends — cheapest and lowest-latency for same-rack links. MikroTik offers SFP+ (S+AO0005, 5 m active), SFP28 (XS+DA0001 / XS+DA0003), QSFP28 (XQ+DA0001 / XQ+DA0003) and 400G QSFP-DD (DDQ+DA0001 / DDQ+DA0003).
• RJ45 copper modules: put a standard Ethernet run into an SFP cage — S-RJ01 (1G) and S+RJ10 (10G over Cat6a to 30 m). Handy when the far end is a copper-only device.

Note copper SFP+ modules (S+RJ10) draw more power and run warmer — check your switch supports them in the intended ports.

6. Going fast: 25G, 100G and beyond

For aggregation and data-center builds, MikroTik’s higher-speed line is a fraction of incumbent pricing:

• SFP28 (25G): XS+31LC10D and XS+85LC01D run 25/10/1G in the same cage — a smooth upgrade path.
• QSFP28 (100G): XQ+31LC02D (single-mode) and XQ+85MP01D (multi-mode), plus the XQ+CM0000-XS+ adapter to run an SFP28 module in a QSFP28 port.
• 200G / 400G: the DQ+BC0003-DS+ breaks a 200G QSFP56 port into 5×50G, and DDQ+85MP01D is a 400G QSFP-DD optic for the newest CRS switches.

7. Compatibility & diagnostics

Because these modules are MikroTik-coded, they pass RouterOS and SwitchOS vendor checks and report clean DDM/DOM telemetry — live optical power, temperature and bias current you can read right in Winbox or the CLI. That diagnostic visibility is a real operational advantage over generic uncoded optics, especially for long single-mode links where you want to watch receive power over time.

An optical link only requires both ends to match on speed, wavelength and fiber type — brands can differ — but running MikroTik optics on MikroTik hardware avoids compatibility flags and keeps diagnostics accurate.

Quick-pick cheat sheet

• Two switches in one rack, 10G → S+AO0005 DAC or S+85DLC03D
• Building A to Building B, 10G, ~2 km → S+31DLC10D (single-mode)
• Tower backhaul, 1G, 40–80 km → S-55DLC80D or CWDM S-C__DLC40D
• Only one fiber strand available → BiDi pair (e.g. S-4554LC80D) or CWDM
• Copper device at the far end → S-RJ01 (1G) / S+RJ10 (10G)
• 25G aggregation uplink → XS+31LC10D
• 100G core / spine → XQ+31LC02D + breakout as needed