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 cost and inventory management argument for the XQ+CM0000-XS+ is straightforward. A 25G SFP28 DAC cable costs USD 15–40 depending on length. A 25G SFP28 optical transceiver costs USD 20–60. A QSFP28 100G optical transceiver costs USD 80–200. For a data centre operator who has a large inventory of 10G SFP+ or 25G SFP28 transceivers and DAC cables — the product of years of network build-out — the XQ+CM0000-XS+ at USD 59.00 allows those existing assets to be reused in new QSFP28-equipped MikroTik switches rather than writing them off and purchasing new 100G optics. The adapter pays for itself on the first transceiver reuse.

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+. Cross-list both products on each other's pages with a combined use-case example: "Use the XS+85LC01D + XQ+CM0000-XS+ to connect a QSFP28 port to a 25G multimode fibre run at USD 59.00 + USD 59.00 — versus a native QSFP28 100G SR4 transceiver at USD 100–200."

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

- **Suggested price:** USD 59.00

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.