3com 100BASE-FX SFP Dual-Mode Transceiver 100Mbit/s networking card

100Base-FX SFP Transceiver Dual Mode 100 Mb Flexibility in Fast Ethernet Connections
Customers with existing FX-based networks can now link directly into selected 3Com Gigabit switches, such as the Switch 5500G-EI family.

This SFP is primarily designed for the following applications:
Businesses running geographically distributed gigabit switching closets up to 2km apart and who do not yet want to run 10-Gigibit links
Businesses who have placed newer gigabit switches in the distribution closet but need to aggregate older Ethernet and Fast Ethernet hubs and switches using 100BASE-FX technology
In situations where gigabit performance is not required, the business is using 50u or 62.5u multimode fiber and needs to run at a distance greater than 550 meters