10GBASE-LR (long reach) is a port type for single-mode fiber and uses 1310 nm lasers. Its 64b/66b PCS is defined in IEEE 802.3 Clause 49 and its PMD sublayer in Clause 52. It delivers serialized data at a line rate of 10.3125 GBd.
The 10GBASE-LR transmitter is implemented with a Fabry–Pérot or Distributed feedback laser (DFB). DFB lasers are more expensive than VCSELs but their high power and longer wavelength allow efficient coupling into the small core of single-mode fiber over greater distances.
10GBASE-LR maximum fiber length is 10 kilometers, although this will vary depending on the type of single-mode fiber used.
