SFP vs SFP+ vs QSFP28: Transceiver Selection Guide

SFP vs SFP+ vs QSFP28: Choosing the Right Transceiver

If you are sourcing network equipment for resale or integration, a transceiver mismatch can cost margin and goodwill. The wrong module means a dead port, a returned order, or a link that comes up at the wrong speed. This guide compares three form factors, SFP, SFP+ and QSFP28 — related by design but serving very different layers of the network. This guide walks through form factors, speeds, reach and connector types, breakout capability, and the compatibility checks to run before ordering. For a broader catalog view, see our range of optical and interface modules.

Form Factor and Speed: What Each One Is For

SFP (1G)

SFP is the classic 1 Gigabit pluggable, roughly the size of a large USB stick, with a single duplex LC connector. It is used in access switching, legacy uplinks, media conversion and industrial networks. SFP ports are one way to add fiber connectivity to an otherwise copper-only switch, and they are found in enterprise wiring closets, campus distribution and factory-floor environments. SFP is also the module type that makes it easy to bridge a copper environment and a fiber backbone one port at a time.

SFP+ (10G)

SFP+ uses the same physical footprint as SFP but is rated for 10 Gigabit Ethernet. You can plug an SFP+ module into many SFP+ ports and, on platforms that support it, use an SFP 1G module in the same cage — but not the reverse. SFP+ ports are used for server access, top-of-rack switching and inter-switch uplinks.

QSFP28 (100G)

QSFP28 is the 100 Gigabit pluggable, and it is physically larger than SFP/SFP+ because it carries four electrical lanes. Each lane runs at 25G to form a 100G aggregate link. QSFP28 ports appear in spine switches, top-of-rack switches for dense compute, and data center aggregation.

Modules Listed on This Site (by part number, not by form factor)

The form-factor descriptions above are general background and are not descriptions of the modules listed on this site. Those modules are identified by part number and listing description only: the GLC-FE-100FX-RGD is listed as a 100Base-FX SFP, the SFP-GE-LX-SM1310 as an eSFP rated 1310 nm and 10 km, and the SFP-10G-LR-S as 10GBASE-LR; the QSFP-40G-SR4-S and GLC-LH-SMD are listed by model name only. A part number is not evidence of form factor, speed, lane configuration, reach, fibre type or connector, so confirm each against the brand data sheet for the exact part number before quoting.

Form Factor Comparison at a Glance

Treat the table as a planning heuristic, not a specification. Exact reach, coding and supported breakout options are defined by the module and by the switch it plugs into.

Reach, Connector Types and Media Choices

In standard naming, SR and LR denote reach classes; for a specific part, confirm the reach class and media on its data sheet rather than inferring them from the part number. SR (short reach) optics run over multimode fiber and are intended for distances at the scale of a rack row or a single floor. LR (long reach) optics run over single-mode fiber for connections that span buildings or a campus. In sourcing conversations, ask for the full part number and the reach class, because the same speed grade comes in multiple optical variants and only one will match the installed cabling.

Connector type follows the form factor. For SFP and SFP+ SR and LR modules, expect duplex LC and confirm it on the data sheet. QSFP28 multimode modules can use an MPO/MTP connector because the four lanes are terminated in parallel; QSFP28 long-reach variants can use duplex LC. If your end customer has pre-terminated MPO trunking, that is a strong signal to quote QSFP28 SR4 rather than SFP+ SR. If they have a fiber run between buildings, single-mode LR optics at 10G or 100G are the option to evaluate.

Media converters and copper variants deserve their own line item. In industrial networks, a module can bridge a copper device into a fiber ring; in office environments, a copper module can extend an existing switch port. List them in the same bill of materials as the switches they connect to.

Breakout: Extracting More From QSFP28 Ports

Breakout is one reason to consider QSFP28 even when the immediate need is 10G or 25G. A single QSFP28 port can be split into four smaller links using a breakout cable or a breakout module, which lets one spine-facing port serve four servers or switches. Typical configurations are 4 x 25G, 4 x 10G or 2 x 40G. Breakout lets fewer high-rate ports serve more endpoints.

Breakout is not universal. It depends on the switch platform, the module and the cabling. Before you commit to a breakout design, confirm three things:

• The switch firmware and port profile support the exact breakout mode you intend to use.
• The module and cable pair are compatible — a breakout in the wrong polarity or lane configuration will not link.
• The port's total power and cooling budget has been considered for the density you are planning.

For a breakout-ready QSFP28 design, verify the breakout cabling against both ends of each link and agree a documented port plan with the integrator before ordering.

Compatibility Checks Before You Quote

Check transceiver compatibility before ordering. Run through this checklist for every opportunity, whether you are supplying 1G access optics or 100G aggregation modules.

• Brand coding. Some switch vendors check the module against a coding scheme, and a module coded for one vendor may be rejected by another. Confirm the target platform's coding requirement before quoting, and match the module to the host switch.
• Speed and port capability. Verify that the port supports the speed you are quoting. A 10G SFP+ module will not run at 10G in a 1G-only SFP cage. Likewise, a QSFP28 port must be configured for 100G or for the breakout mode you intend.
• Wavelength and fiber pairing. Match the module's wavelength and reach class to the fiber type in the ground: multimode SR optics for multimode runs, single-mode LR optics for single-mode runs. On bidirectional or CWDM links, confirm that the two ends are paired — one module's transmit wavelength must match the other's receive wavelength.
• Connector and polarity. Duplex LC has a fixed polarity; MPO trunking has polarity schemes that must match the module orientation. A polarity mismatch produces a clean-looking cable and a dead link.
• DOM and management. If the customer relies on digital optical monitoring for link budgeting, confirm the module reports DOM data and that the platform reads it.
• Power and thermal. Dense QSFP28 line cards and long-reach optics can run hot. Check the port's supported power envelope rather than assuming any module will fit.

If you are uncertain about a specific model, request the host switch model and firmware version from the customer and confirm against that, not against a generic family name.

Stocking and Sourcing Strategy for Importers and Distributors

Decide the transceiver mix from the networks your own customers run and the project requirements in hand: which speeds (1G SFP, 10G SFP+, QSFP28), which reach classes, and in what quantities. Placing each listed part number into one of those layers should be done from its data sheet, not from its model name.

Because buyers cannot predict which brand a project will specify until the RFQ arrives, plan for coding flexibility as well as quantities. Whatever the mix, confirm availability and delivery time per exact part number before committing a project schedule. For QSFP+ and QSFP28 background and the listed QSFP-40G-SR4-S (model name only), see the QSFP selection notes.

When you request a quote, include the host switch make and model, the module part number you want, the fiber type and distance, and the quantity.

A Short Selection Walkthrough

• Access layer: SFP 1G SR or LR depending on the fiber run from closet to desk or device.
• Server and uplink layer: SFP+ 10G SR inside the row, SFP+ 10G LR between buildings or across a campus.
• Aggregation and spine: QSFP28 100G SR4 inside the row, long-reach variants between sites, with breakout where the server count justifies it.

Map the model to the installed fiber before you map it to the price list.

Sourcing Note

Hui Tong is a supplier and exporter of original, brand-new network equipment, including switches, routers, firewalls, servers, NAS storage and transceivers, with minimum orders from one unit, payment by T/T, D/P or D/A, and a one-year warranty. The company profile states that it has offices and warehouses in Shanghai, Beijing, Wuhan and Shenzhen, and lists main export markets including North America, Europe, the Middle East, Southeast Asia, Africa and Oceania. Listed modules include the SFP-10G-LR-S (10GBASE-LR) and the QSFP-40G-SR4-S (model name only); browse the full listed range of optical and interface modules and the QSFP selection notes, then send the host switch model and fiber details with your RFQ, and confirm the specification, availability, price and delivery time of each part before ordering.