Dual fiber modules are generally easier to manage and deploy, without the need for wavelength-matched pairs. One of the most common decisions network engineers face is selecting between single fiber SFP and dual fiber SFP modules. BIDI module only has 1 port, wave filtering through the filter of module, and finished the transmitting of 1310nm optical signal. Single fiber modules (BiDi) use one fiber for both transmitting and receiving data. They use a thin fiber. SFP (Small Form-factor Pluggable) is a compact, hot-pluggable network interface module used to connect network devices (switches, routers, firewalls) to fiber optic or copper cables.
[pdf] SFP ports are modular network interfaces used to connect switches, routers, servers, and fiber optic links through interchangeable transceiver modules. Unlike standard RJ45 Ethernet ports, SFP ports can support both fiber optic and copper Ethernet connections depending on the installed module. Think of it as the “translator” for your network equipment, converting electrical signals into optical signals. Small Form-factor Pluggable (SFP) is a compact, hot-pluggable network interface module format used for both telecommunication and data communications applications. Transceiver compatibility is a key concern in enterprise network deployments.
[pdf] Protective relays are power system protection devices that monitor current, voltage, frequency, impedance, or differential quantities and command circuit breakers when faults or abnormal conditions occur. Engineering use: Relays are used on feeders, transformers, buses, motors, generators, and transmission lines to protect equipment and improve system. A protective relay is an intelligent electrical device designed to detect faults in power systems and initiate corrective actions such as tripping a circuit breaker. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions.
[pdf] 
