SFP 1G BiDi (Bidirectional) stands for Small Form-factor Pluggable 1 Gigabit Bidirectional transceiver module. This type of SFP module is designed for bi-directional communication over a single fiber optic strand, allowing for the transmission and reception of data on the same fiber using different wavelengths. BiDi technology is particularly useful in situations where the availability of fiber strands is limited, making it a cost-effective and efficient solution for certain network setups.