MikroTik XQ+CM0000-XS+ QSFP28 to SFP28 Converter

The MikroTik XQ+CM0000-XS+ solves a specific and common data centre and ISP infrastructure problem: a switch has QSFP28 100G/40G ports, and the operator needs to connect a device — a server, a storage array, an upstream switch, or a legacy network device — that has only an SFP28 25G, SFP+ 10G, or SFP 1G interface. Without the XQ+CM0000-XS+, the options are a separate 25G switch layer (additional hardware, cost, rack space, and power), a breakout cable (which splits one QSFP28 port into four 10G SFP+ connections but requires breakout-capable optics at both ends), or leaving the QSFP28 port unused. With the XQ+CM0000-XS+, the operator inserts any compatible SFP / SFP+ / SFP28 module or DAC cable into the converter, plugs the converter into the QSFP28 port, and the QSFP28 port operates at 1G, 10G, or 25G — determined by the inserted module's speed tier.

The physical mechanism of the XQ+CM0000-XS+ is a QSA (QSFP28 to SFP28 adapter) — a mechanical and electrical adapter that presents a QSFP28 physical interface to the host switch port and an SFP28 electrical interface to the inserted transceiver. The host switch's QSFP28 port negotiates the data rate with the inserted SFP / SFP+ / SFP28 module through the adapter, operating the QSFP28 port at the module's speed rather than at its native 100G or 40G maximum. The QSFP28 port's unused lanes are simply inactive — a QSFP28 port running a single 25G SFP28 module through the XQ+CM0000-XS+ operates on one of its four 25G lanes with the other three inactive.

The tri-rate 1G / 10G / 25G support covers the three most common SFP form-factor speeds in current network infrastructure:

- **1G SFP:** Legacy 1000BASE-SX, 1000BASE-LX, or 1000BASE-T SFP modules for connecting legacy Gigabit devices directly to a QSFP28-equipped switch.

- **10G SFP+:** The dominant 10GbE module tier — SR (multimode 850nm), LR (single-mode 1310nm), DAC cables, and AOC cables. For operators with an existing 10G SFP+ transceiver and DAC cable inventory, the XQ+CM0000-XS+ allows those modules to be used in new QSFP28-equipped switches without a separate 10G switch layer.

- **25G SFP28:** The current server connectivity tier — 25GBASE-SR (multimode 850nm, 100m), 25GBASE-LR (single-mode, 10km), DAC cables. Operators deploying the CRS520-4XS-16XQ-RM with its 16× QSFP28 ports can use SFP28 25G transceivers — including the MikroTik XS+85LC01D — in the QSFP28 ports via the XQ+CM0000-XS+ without requiring native QSFP28 100G optics.

The primary compatible MikroTik devices are explicitly called out by MikroTik's own product description:

- **CRS504-4XQ-IN:** 4× QSFP28 100G ports — a compact desktop switch where the XQ+CM0000-XS+ converts any or all four QSFP28 ports to SFP28 25G / SFP+ 10G / SFP 1G as required by the connected devices.

- **CRS518-16XS-2XQ-RM:** 16× SFP28 25G + 2× QSFP28 100G rackmount switch — the 2× QSFP28 uplink ports can use the XQ+CM0000-XS+ to connect to 25G or 10G upstream devices rather than requiring native 100G uplink optics.

- **CRS510-8XS-2XQ-IN:** 8× SFP28 25G + 2× QSFP28 100G desktop switch — same QSFP28 uplink flexibility as the CRS518.

- **CRS520-4XS-16XQ-RM:** 16× QSFP28 40G + 4× SFP28 25G — operators who do not yet have 40G QSFP+ optics or DAC cables can use the XQ+CM0000-XS+ to populate QSFP28 ports with available SFP28 25G modules during a phased 40G/100G migration.

The energy efficiency claim in MikroTik's own product description reflects the power draw of a passive adapter versus an active switch layer. A separate 25G switch layer (a CRS518 or equivalent) consuming 50–100W replaces a passive adapter consuming near-zero power — the XQ+CM0000-XS+ draws only the power of the inserted transceiver module, with no active electronic components adding to the power budget. For a data centre where power density and cooling are constrained, eliminating an intermediate switch layer by using QSA adapters is a meaningful power and cooling efficiency improvement.

The -20°C to +85°C tested ambient temperature range covers standard data centre and equipment room operating conditions with significant margin — the same upper limit as the XS+85LC01D transceiver. The +85°C upper limit provides thermal margin in densely packed switch chassis.

**Canadian market note:** No certifications are published on the XQ+CM0000-XS+ product page. The adapter is a passive electrical and mechanical converter with no active transmitter or receiver — no ISED wireless certification applies. Confirm any applicable Canadian import or electrical safety certification requirements with your distributor.

**Pairing with XS+85LC01D:** The XQ+CM0000-XS+ and the XS+85LC01D (MikroTik's tri-rate 1G/10G/25G multimode SFP28 transceiver) are direct companion products. The XS+85LC01D inserted into the XQ+CM0000-XS+ adapter allows a QSFP28 port to operate at 25G over multimode fibre — combining the tri-rate transceiver flexibility of the XS+85LC01D with the QSFP28 port conversion of the XQ+CM0000-XS+. 

Key specifications:

- **Product code:** XQ+CM0000-XS+

- **Format:** QSFP28 (host) to SFP / SFP+ / SFP28 (module)

- **Supported data rates:** 1G / 10G / 25G

- **Compatible module formats:** SFP, SFP+, SFP28

- **Type:** Passive QSA adapter (no active components)

- **Tested ambient temperature:** -20°C to +85°C

- **MTBF:** ~100,000 hours at 25°C

- **Certifications:** Not published — confirm from brochure

- **Compatible MikroTik devices:** CRS504-4XQ-IN, CRS518-16XS-2XQ-RM, CRS510-8XS-2XQ-IN, CRS520-4XS-16XQ-RM — confirm full compatibility list from MikroTik documentation

Note: Passive adapter only — no active signal regeneration. Maximum data rate limited to 25G (SFP28 tier) — does not enable 100G operation from SFP28 modules. Confirm host switch QSFP28 port compatibility with QSA adapters from MikroTik's wired interface compatibility documentation before deployment.