You can connect a gigabit SFP optical module to a 100Mbps connection using a 10/100/1000M adaptive electrical port module (SFP copper-T converter) that supports auto-negotiation.

Using an SFP Copper-T Electrical Module

To connect a gigabit optical SFP module to a 100Mbps network, you can use an SFP electrical port module (also called a copper-T module) that converts the optical interface to a standard RJ45 Ethernet port:

• Insert the electrical port module into the SFP slot of your switch or device.
• Connect a Cat5e or Cat6 cable from the RJ45 port of the module to the 100Mbps network device.
• The module supports 10/100/1000Mbps auto-negotiation, so it will automatically adjust to the 100Mbps speed of the connected device.
• This setup is plug-and-play and does not require additional configuration .

Key Considerations

• Module Type: Use a 10/100/1000M adaptive module (e.g., ETU-Link ES-T2-R) for compatibility with 100Mbps networks. Pure gigabit modules (ES-T1-R) may not auto-negotiate down to 100Mbps.
• Cable Requirements: Use Cat5e or Cat6 UTP cables for reliable transmission up to 100 meters.
• Full Duplex Support: These modules support full-duplex operation, ensuring proper communication even at lower speeds.
• SFP Compatibility: Ensure the SFP module is compatible with your switch or router, and the device supports the SFP copper-T module .

Alternative Approach

If you do not have a copper-T module, you can also:

• Use a switch that supports both 100Mbps and 1Gbps SFP ports, allowing the optical module to connect to the switch, which then downshifts the speed to 100Mbps for legacy devices.
• Ensure auto-negotiation is enabled on both ends to prevent speed mismatch issues . By using an SFP copper-T module or a compatible switch, you can safely connect a gigabit optical module to a 100Mbps network without manual configuration, maintaining network stability and proper data transmission.