The Fujitsu FC9681EL4M EXT SH OC-3/12 Unit Optical Network Telecom Module is a plug-in module designed for use with the Fujitsu FLASHWAVE 4100 product line. This unit features two external optical interfaces, with compatibility for OC-3 and OC-12 ports. With its compact dimensions of 10 x 12 x 4 inches, this module is specifically designed for networking applications, offering high-speed communication capabilities through its proprietary backplane interface. Perfect for enhancing network connectivity and performance, this optical network module from Fujitsu is a reliable and efficient choice for businesses and networking setups.