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The C-LIGHT CLOTU4QSFPXZR4 is a QSFP28 optical transceiver designed for 100G/OTU4 ZR4 point-to-point connectivity over single-mode fiber. Supporting transmission distances of up to 100 km with host-side KR4 forward error correction (FEC) enabled, it provides a long-reach optical interface for telecommunications transport, metro networks, and other high-capacity optical connections.
The module uses four LAN-WDM wavelengths, an EML-based optical transmitter, and an SOA+PIN receiver. Its duplex LC connector provides separate transmit and receive fiber paths, while the QSFP28 package integrates high-speed electrical and optical interfaces into a compact form factor for network equipment.
With a maximum power consumption of 5.5 W, a single 3.3 V power supply, and digital diagnostic monitoring, the CLOTU4QSFPXZR4 is designed for long-distance 100G optical links where reach, interface compatibility, and optical performance are central to network planning.
1. Product Overview and Key Features
The CLOTU4QSFPXZR4 combines a QSFP28 interface with LAN-WDM optics for long-reach 100G and OTU4 applications. Its four optical lanes operate at different wavelengths, allowing the module to multiplex multiple high-speed channels over a duplex single-mode fiber connection.
Key Features
100G/OTU4 connectivity: Designed for 100G/112G ZR4 point-to-point optical links.
Up to 100 km reach: Supports long-distance single-mode fiber links with host-side KR4 FEC enabled for the specified reach.
Four LAN-WDM wavelengths: Uses four wavelength channels centered around 1295 nm, 1300 nm, 1305 nm, and 1309 nm.
EML optical transmitter: Uses an electro-absorption modulated laser for optical signal transmission.
SOA+PIN receiver: Combines a semiconductor optical amplifier with a PIN photodiode receiver.
Duplex LC connector: Provides separate optical paths for transmission and reception over single-mode fiber.
QSFP28 form factor: Supports integration into compatible high-speed switches, routers, and optical transport equipment.
Digital diagnostics: Provides a two-wire serial management interface with digital diagnostic monitoring.
Power and temperature: Operates from a single 3.3 V supply, with maximum power consumption of 5.5 W and a case operating temperature of 0°C to 70°C.
2. Technical Specifications
The CLOTU4QSFPXZR4 combines long-reach LAN-WDM optics with the electrical and mechanical characteristics of a QSFP28 module.
| Parameter | Specification |
|---|---|
| Product model | CLOTU4QSFPXZR4 |
| Form factor | QSFP28 |
| Application | 100GE/OTU4 |
| Data rate listed in datasheet | 100G / 112G |
| Optical application | 100/112GBASE-ZR4 point-to-point links |
| Maximum transmission distance | Up to 100 km over single-mode fiber, with host-side KR4 FEC enabled |
| Optical multiplexing | Four LAN-WDM wavelength channels |
| Transmitter | LAN-WDM EML laser |
| Receiver | SOA+PIN |
| Optical connector | Duplex LC |
| Electrical interface | CAUI-4, compliant with IEEE 802.3bm-2015 as specified in the datasheet |
| Power supply | Single +3.3 V |
| Maximum power consumption | 5.5 W |
| Operating case temperature | 0°C to +70°C |
| Digital management | Two-wire serial interface with digital diagnostic monitoring |
| Module standards | SFF-8661 Rev. 2.5 and SFF-8636 Rev. 2.10a |
| Environmental compliance | RoHS compliant, as specified in the datasheet |
| Laser classification | Class 1 |
3. Four-Lane LAN-WDM Optical Architecture
The CLOTU4QSFPXZR4 uses four LAN-WDM wavelength channels to carry its optical data. Each channel operates around a specified wavelength, allowing the signals to be combined within the optical interface and separated at the receiver.
LAN-WDM multiplexing makes it possible to transmit multiple optical lanes over a single fiber in each direction. The duplex LC interface uses one fiber for transmission and another for reception, providing bidirectional connectivity across the same link.
LAN-WDM Wavelength Specifications
| Optical Lane | Minimum Wavelength | Typical Wavelength | Maximum Wavelength |
|---|---|---|---|
| L0 | 1294.53 nm | 1295.56 nm | 1296.59 nm |
| L1 | 1299.02 nm | 1300.05 nm | 1301.09 nm |
| L2 | 1303.54 nm | 1304.58 nm | 1305.63 nm |
| L3 | 1308.09 nm | 1309.14 nm | 1310.19 nm |
The wavelength spacing allows the four optical channels to coexist within the LAN-WDM system. Correct operation depends on using compatible optical equipment and maintaining the link within the module's specified optical power range.
For installation, the duplex LC connectors should be connected to the correct transmit and receive paths. Connector cleanliness, fiber condition, polarity, and insertion loss all contribute to reliable operation over long distances.
4. Optical Transmitter Performance
The module uses an EML-based LAN-WDM transmitter designed for high-speed optical transmission. The transmitter specifications define wavelength accuracy, launch power, extinction ratio, and other parameters that influence the quality of the signal delivered to the fiber.
Selected Transmitter Specifications
| Parameter | Symbol | Minimum | Typical | Maximum | Unit |
|---|---|---|---|---|---|
| Side-mode suppression ratio | SMSR | 30 | — | — | dB |
| Total average optical launch power | POUT | — | — | 12.5 | dBm |
| Average optical launch power per lane | POUTL | 4 | — | 6.5 | dBm |
| Average launch power with transmitter disabled, per lane | POUT_OFF | — | — | -30 | dBm |
| Extinction ratio | ER | 8 | — | — | dB |
| Spectral width | Δλ | — | — | 1 | nm |
| Optical modulation amplitude per lane | OMA | 3.5 | — | 7 | dBm |
| Transmitter and dispersion penalty per lane | TDP | — | — | 2.2 | dB |
| OMA minus TDP per lane | OMA-TDP | 1.5 | — | — | dBm |
| Maximum difference in OMA between lanes | DT_OMA | — | — | 4 | dB |
These transmitter parameters support assessment of signal strength, wavelength characteristics, and optical quality. For link engineering, the transmitter limits must be evaluated together with receiver sensitivity, fiber attenuation, connector losses, and the required transmission distance.
5. Receiver Sensitivity and Long-Reach Operation
The receiver combines a semiconductor optical amplifier (SOA) with a PIN photodiode. This receiver architecture supports the long-reach optical application by providing gain and photodetection within the optical receive path.
The datasheet lists receiver sensitivity values at two lane-rate conditions. At the higher 27.95G lane rate, the specified OMA sensitivity is -28 dBm. This aligns with the product's stated 100 km application when the host has KR4 FEC enabled.
Selected Receiver Specifications
| Parameter | Symbol | Specified Value | Unit |
|---|---|---|---|
| Receiver sensitivity, OMA per lane at 25.78G | — | -30 maximum | dBm |
| Receiver sensitivity, OMA per lane at 27.95G | — | -28 maximum | dBm |
| Average received optical power per lane | — | -28 to -5 | dBm |
| Received optical power in OMA, overload limit | OMA | -4.5 maximum | dBm |
| Receiver damage threshold | Pin, damage | -2.5 | dBm |
| Receiver reflectance | RXR | -26 maximum | dB |
| Loss-of-signal assert level | LOSA | -40 minimum | dBm |
| Loss-of-signal de-assert level | LOSD | -30 maximum | dBm |
| Loss-of-signal hysteresis | LOSH | 0.5 minimum | dB |
The receiver sensitivity figures are associated with the datasheet's specified conformance test conditions. They should be used together with the complete optical interface requirements rather than treated as an independent guarantee of reach under every field condition.
KR4 FEC and the 100 km Link
For the specified 100 km reach, the host-side KR4 forward error correction (FEC) must be enabled. FEC adds error-correction capability to the transmitted data and helps the link meet its required error performance under the specified operating conditions.
The host interface and network configuration must support the required FEC mode. Before deployment, confirm switch or router support, port configuration, module interoperability, and the FEC settings at the connected endpoints.
Long-reach links should also be evaluated against the actual optical budget. Fiber attenuation, connector insertion loss, splices, patch panels, and the condition of the installed fiber all affect received power. A nominal 100 km rating does not remove the need for end-to-end optical validation.
6. Host Interface, Power, and Operating Conditions
QSFP28 and CAUI-4 Interface
The CLOTU4QSFPXZR4 uses the QSFP28 form factor and a CAUI-4 high-speed electrical interface. The datasheet identifies compliance with the QSFP28 standards SFF-8661 Rev. 2.5 and SFF-8636 Rev. 2.10a, as well as IEEE 802.3bm-2015 for the electrical interface.
Before ordering, verify that the target switch, router, or optical transport equipment supports the module's intended 100GE/OTU4 application. Host compatibility includes more than mechanical fit; port configuration, interface support, firmware, and KR4 FEC capability must also match the deployment.
Power Consumption and Temperature
The module operates from a single +3.3 V power supply and has a maximum power consumption of 5.5 W. Its specified case operating temperature range is 0°C to +70°C.
These limits should be considered when installing multiple optical modules in a switch or transport system. The host must provide sufficient power and airflow to maintain suitable operating conditions. High module density and elevated ambient temperatures can make thermal planning especially important.
Digital Diagnostic Monitoring
The module includes a two-wire serial interface with digital diagnostic monitoring. Depending on host support and the information exposed by the module, monitoring data can help operators assess operating conditions and investigate link issues.
During commissioning, check module recognition, operating temperature, optical transmit and receive levels where available, and relevant interface alarms. Recording baseline readings at installation can also support later troubleshooting.
7. Applications for the QSFP28 ZR4 100km Transceiver
Metropolitan and Telecommunications Transport
Telecommunications networks often need 100G connectivity between aggregation nodes, transport facilities, and remote network locations. The CLOTU4QSFPXZR4 provides a long-reach optical interface for compatible links that extend up to 100 km over single-mode fiber when the required host-side FEC is enabled.
Long-Distance Data Center Interconnections
Data center infrastructure may require connections between facilities or network locations beyond the reach of conventional shorter-distance 100G optics. The ZR4 100 km interface can support these deployments when the optical route, host equipment, and link budget meet the module's specifications.
Enterprise and Service Provider Backbones
Large enterprise networks and service providers use high-capacity optical links to connect remote sites, aggregation systems, and backbone equipment. The module's QSFP28 package supports integration into compatible platforms, while LAN-WDM provides the optical channels required for the specified long-reach link.
OTU4 and 100GE Transport
The datasheet lists 100GE/OTU4 as the application and 100G/112G as the data rate. This makes the module relevant to compatible Ethernet and optical transport deployments. Equipment documentation should be checked to establish support for the intended application and interface configuration.
8. Deployment and Compatibility Requirements
The CLOTU4QSFPXZR4 should be selected against the complete link and host requirements. Confirm the following before deployment:
Host compatibility: The platform supports the QSFP28 module and the intended 100GE/OTU4 ZR4 application.
FEC configuration: KR4 FEC is enabled at the host for the specified 100 km reach.
Optical path: The single-mode fiber route and total insertion loss fit within the required optical budget.
Connector condition: Duplex LC connectors are clean, correctly connected, and suitable for the installed fiber.
Received optical power: Both directions remain within the specified receiver operating range.
Power and cooling: The host meets the module's power, airflow, and operating temperature requirements.
Monitoring and alarms: Module recognition and supported diagnostic functions operate as expected on the target equipment.
After installation, verify link establishment at the intended rate, confirm the required FEC configuration, inspect available optical diagnostics, and test the link according to the network's acceptance criteria. These checks help ensure that the interface performs as required over the complete optical route.
9. Conclusion
The C-LIGHT CLOTU4QSFPXZR4 is a QSFP28 100G/OTU4 ZR4 optical transceiver designed for long-reach point-to-point links up to 100 km over single-mode fiber. Its four LAN-WDM wavelengths, EML transmitter, SOA+PIN receiver, duplex LC connector, and digital diagnostic monitoring support high-capacity optical transport over extended distances.
With a maximum power consumption of 5.5 W and an operating case temperature range of 0°C to +70°C, the module is suited to compatible equipment designed for its electrical and thermal requirements. The specified 100 km reach requires host-side KR4 FEC to be enabled, along with a suitable optical link budget and compatible endpoint equipment.
For telecommunications transport, data center interconnections, and long-distance enterprise or service provider links, the CLOTU4QSFPXZR4 provides a 100G-class optical connectivity option where the host interface, FEC configuration, and fiber path meet the product specifications.
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