Finisar’s FCMJ-8520/8521-3 1000BASE-T Copper Small Form Pluggable (SFP) transceivers are based on the SFP Multi Source Agreement (MSA)1 . They are compatible with the Gigabit Ethernet and 1000BASE-T standards as specified in IEEE Std 802.32 . The 1000BASE-T physical layer IC (PHY) can be accessed via I2C, allowing access to all PHY settings and features. The FCMJ-8520-3 uses the SFP’s RX_LOS pin for link indication, and 1000BASE-X auto-negotiation should be disabled on the host system. The FCMJ-8521-3 is compatible with 1000BASE-X auto-negotiation, but does not have a link indication feature (RX_LOS is internally grounded). See AN-2036, “Frequently Asked Questions Regarding Finisar’s 1000BASE-T SFPs”, for a more complete explanation on the differences between the two models and details on applications issues for the products.
