100G QSFP28 LR4 FAQ: Expert Answers to Technical & Deployment Questions

Overview & Thematic Scope

Welcome to our technical FAQ for the 100G QSFP28 LR4 optical transceiver. This module is a cornerstone for high-speed data center interconnects and enterprise core networks, designed for long-reach 100G Ethernet links. In this guide, we answer the most critical pre-sales and post-sales questions, focusing on the maximum transmission distance, optical specifications, compatibility, and common troubleshooting scenarios to help network engineers and procurement specialists make informed decisions.

Frequently Asked Questions

What is the maximum distance for a 100G QSFP28 LR4 module?

The maximum transmission distance for a 100G QSFP28 LR4 module is 10 kilometers (6.2 miles) over standard single-mode fiber (SMF). This 10km reach is defined by the IEEE 802.3ba 100GBASE-LR4 standard and is achieved using four LAN-WDM wavelengths in the 1310nm band, which are multiplexed onto a single pair of fiber optic cables via a duplex LC connector .

What are the key optical specifications for the 100G QSFP28 LR4?

Key specifications include a total data rate of 103.125 Gbps (4×25.78Gbps NRZ channels) and an operating distance of up to 10km on G.652 single-mode fiber . The module typically operates with a power consumption between 3.5W and 4.5W and uses four specific LAN-WDM wavelengths centered around 1295.56nm, 1300.05nm, 1304.58nm, and 1309.14nm . The transmitter average launch power ranges from -4.3 dBm to +4.5 dBm per lane, with a receiver sensitivity of better than -10.6 dBm .

Can a 100G QSFP28 LR4 module connect to a 100G CFP LR4 module?

Yes, a 100G QSFP28 LR4 module is generally interoperable with a 100G CFP LR4 module, provided the modules are from compatible brands. Both module types operate at a 100Gbps transmission rate and use the same LAN-WDM wavelengths in the 1310nm band. This makes them interoperable for standard 100GBASE-LR4 links. However, it is always recommended to verify compatibility with your specific network equipment vendor .

Does using a third-party compatible QSFP28 LR4 module void my equipment warranty?

No, using a compatible third-party 100G QSFP28 LR4 module typically does not void your manufacturer’s equipment warranty. The manufacturer is obligated to honor the warranty and provide support unless the equipment defect was directly caused by the use of the third-party optics. This industry-standard practice allows for cost-effective sourcing of optical modules .

What are common link issues and troubleshooting steps for QSFP28 LR4 modules?

Common link-up issues are often related to configuration mismatches (e.g., speed, FEC settings) or dirty optical connectors . For troubleshooting, ensure the port is configured for 100G speed (e.g., 4 lanes, NRZ encoding) and that Forward Error Correction (FEC) settings like ‘rs’ are correctly applied . Always clean the optical connectors with a proper fiber optic pen cleaner before reconnecting, as dust and contaminants are a frequent cause of reduced optical launch power or erratic readings . If diagnostic readings are abnormal but traffic is fine, the module’s register read function may be faulty and require replacement .

What is the power consumption of a 100G QSFP28 LR4 transceiver?

The typical power consumption for a 100G QSFP28 LR4 module is approximately 3.5 Watts to 4.0 Watts. This energy-efficient power profile is a key advantage of the QSFP28 form factor, allowing for high-density port configurations in data center switches without exceeding power budgets .

Will a 100G QSFP28 LR4 work on the 1310nm channel of a CWDM Mux/Demux?

No, a 100G QSFP28 LR4 module will not work on the 1310nm channel of a standard 18-channel CWDM Mux/Demux. The LR4 uses four LAN-WDM wavelengths, which are a specific subset within the 1310nm band. The CWDM Mux/Demux requires a dedicated, separate 1310nm channel, and using it can cause conflicts that prevent the module from operating correctly .