The Cisco CFP-100G-LR4 is a 100 gigabit single mode fiber Ethernet adapter which is used with their 9500 series enterprise switches. These adapters usually cost around $5000 each and usually have a lifetime warranty.
Optical fiber uses 2 connection, TX and RX to simplify designs. Most fiber based hardware uses extremely powerful lasers to overcome the inherent attenuation of the signal.
The CFP-100G-LR4 is designed for up to 10km links which is commonly called the campus area network however this distance also spans the metropolitan area network as well.
Using the higher speed makes sense with copper networks now operating largely at 10GBASE-T speeds, the faster 100GBASE-LR4 links can eliminate bottlenecks between buildings.