A 100G QSFP28 optical transceiver connects a switch, router, or other network device to fiber-optic cabling at a nominal aggregate data rate of 100 Gbps. To choose the right module, match its optical type and reach to your fiber plant, then verify the host equipment’s compatibility, connector, and operating requirements. Common options include SR4 for short-reach multimode links, LR4 for longer-reach single-mode links, and CWDM4 or PSM4 for specific single-mode applications. This guide explains their differences and offers a practical framework for evaluating modules before purchase.
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This guide is intended for network engineers, data-center operators, system integrators, and procurement teams specifying 100G links. It is useful when planning a new deployment, expanding an existing network, or replacing transceivers in switches and routers. Buyers comparing suppliers can also use the selection criteria and checklist to clarify technical and sourcing requirements.
QSFP28 describes a compact, hot-pluggable transceiver form factor designed for 100G-class connections. A module converts electrical signals from the host device into optical signals for fiber transmission, and converts incoming optical signals back into electrical signals. A typical design uses four electrical lanes, each operating at approximately 25.78 Gbps, to support the 100 Gbps aggregate data rate.
The optical side depends on the module type. Some modules send data over multiple parallel fiber paths, while others use several wavelengths over a duplex fiber pair. These approaches affect the required cabling, connector, reach, and installation cost, so modules with the same QSFP28 form factor are not automatically interchangeable in a link.
100GBASE-SR4 is commonly used for short connections over multimode fiber, including links within a data hall. It uses parallel optical lanes and typically connects through an MPO/MTP-style interface with eight active fibers. Typical reach is up to 70 m on OM3 fiber or 100 m on OM4 fiber; actual limits should be checked against the module datasheet and the installed cabling.
SR4 can be a practical choice when multimode infrastructure is already available. However, it requires compatible parallel-fiber cabling and polarity management, so confirm the complete path—including patch panels and trunk cables—before ordering.
100GBASE-LR4 is designed for single-mode fiber links with a typical maximum reach of 10 km. It transmits using multiple wavelengths over a duplex fiber connection, commonly with LC connectors. This can suit campus, building-to-building, or other longer links where single-mode cabling is installed.
LR4 is not simply a longer-reach replacement for SR4: the fiber type, connector, optical budget, and module cost differ. Verify that the host port supports the specific transceiver and that the proposed link remains within its specified reach and optical limits.
100G CWDM4 modules typically support links up to 2 km over single-mode fiber using four wavelengths and a duplex LC interface. They can be considered where a buyer wants a 100G connection over a two-fiber single-mode path at shorter distances than LR4 is designed for. CWDM4 is associated with multi-source specifications, so check the exact module implementation and host compatibility rather than assuming every product has identical behavior.
100G PSM4 typically supports reach up to 500 m over parallel single-mode fiber and uses an MPO-style connector. It transmits across separate fiber paths rather than multiplexing the wavelengths onto a duplex pair. PSM4 can be relevant where parallel single-mode cabling is planned, but it may require more fiber strands and different cabling management than a duplex interface.
| Module type | Typical reach | Fiber | Common interface | Typical use |
|---|---|---|---|---|
| 100GBASE-SR4 | 70 m on OM3; 100 m on OM4 | Multimode | MPO/MTP-style | Short data-center links |
| 100GBASE-LR4 | Up to 10 km | Single-mode | Duplex LC | Longer campus or building links |
| 100G CWDM4 | Typically up to 2 km | Single-mode | Duplex LC | Short-to-medium single-mode links |
| 100G PSM4 | Typically up to 500 m | Parallel single-mode | MPO/MTP-style | Links using parallel fiber paths |
Reach figures in this table are common application values, not a guarantee for every product or installed link. Connector loss, fiber quality, patching, and the transceiver’s specified optical budget can affect whether a link operates reliably. Always use the product datasheet and the network equipment manufacturer’s requirements for final validation.
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Start with the switch or router model, port type, firmware requirements, and supported transceiver list. Some equipment applies vendor-specific coding or validation, so confirm whether the host accepts the proposed module before placing an order. Provide the supplier with the equipment brand, model, and port details to support a more accurate compatibility review.
Identify the actual path length, fiber category, and any intermediate patch panels. Choose a module whose specified reach covers the complete optical path, rather than only the distance between two racks. If the fiber type or route is uncertain, document the installed cabling and request a review before selecting between multimode, duplex single-mode, and parallel-fiber options.
Confirm whether the installation uses LC or MPO/MTP-style connectors and whether the link is duplex or parallel. For MPO-based links, verify fiber count, polarity, and breakout requirements. A mismatch between the module and cabling plan can lead to extra patching, replacement parts, or commissioning delays.
Compare the module’s wavelength, transmit and receive specifications, power consumption, temperature range, and digital diagnostic monitoring support with the project requirements. For example, a listed reach alone does not confirm that a module will work with a particular fiber route; the optical budget and connection losses also matter. Review the full datasheet and clarify any environmental or monitoring requirements with the supplier.
Pricing and availability depend on module type, quantity, compatibility requirements, and supply conditions. Ask suppliers to confirm the applicable MOQ, lead time, warranty terms, customization options, and what pre-shipment checks are included. Requesting a quotation with a defined equipment model and cable specification makes it easier to compare equivalent products rather than price alone.
OPTEKCOM supplies fiber-optic equipment, including optical transceivers and interconnect products. For a 100G QSFP28 requirement, our team can review the application details provided and help identify the relevant module type and purchasing specifications. Confirm product availability, compatibility, and commercial terms for your specific project during the quotation process.
One frequent mistake is choosing a module based only on the “100G QSFP28” label. That description does not specify reach, fiber type, connector, or host compatibility. Another is overlooking the installed cabling: a module with the right nominal reach still cannot solve a connector, polarity, or fiber-category mismatch.
Buyers should also avoid treating typical reach figures as unconditional guarantees. Validate the full link path, including patch connections, and check the optical specifications in the product documentation. If the project uses breakout cables, confirm that the switch configuration, port behavior, and cable design support the intended connection.
The right 100G QSFP28 optical transceiver is the one that matches the host device, fiber plant, link distance, connector, and operating requirements. SR4 is commonly suited to short multimode links, LR4 to longer duplex single-mode links, CWDM4 to duplex single-mode paths typically up to 2 km, and PSM4 to parallel single-mode links typically up to 500 m. These reach values are useful starting points, but the datasheet and end-to-end link design should guide the final decision.
Before requesting a quote, prepare the equipment model, desired quantity, link distance, fiber type, connector format, and required delivery schedule. OPTEKCOM can use these details to discuss suitable 100G QSFP28 options and provide project-specific availability and commercial information. This step helps your team compare compatible solutions and reduce avoidable sourcing and installation issues.
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