The LevelOne SFP-9331 is a high performance, cost-effective SFP transceiver. It provides up to 1.25 Gbps bi-directional data transfer rate at distances up to 20km on a single fiber core. These bi-directional SFP Transceivers allow data transfer in either direction through a single optical fiber by employing separate wavelengths traveling in either direction.The SFP-9331 transmits using a wavelength of 1550nm and receives using a wavelength of 1310nm. When coupled with the LevelOne SFP-9321 transceiver which transmits at and receives at the opposite rates you get bi-direction data communication on a single fiber core.