The X2 transceiver is a 10 gigabit per second modular fiber optic interface designed for use in routers,  switches and optical transport platforms. It is an early generation 10 gigabit interface related to XENPAK and XPAK formats. X2 can be used with 10 gigabit ethernet or OC-192 / STM-64 speed SDH / SONET equipment.
X2 modules are smaller and consume more power than first generation XFP modules, but larger and more energy efficient than the standard XFP transceiver and standard SFP +.
As of 2016 this format is relatively uncommon and has been replaced by 10Gbit / s SFP + in most new equipment.
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