There are the common types of optical passive components：

Optical Connectors:

Purpose: Connect optical fibers together, allowing the transmission of light signals between them.  

Types: 

l SC: Standard connector, widely used for its simplicity and reliability.  

l ST: Straight tip connector, known for its ease of insertion and removal.  

l FC: Ferrule connector, provides high precision and repeatability.  

l LC: Lucent connector, compact and suitable for high-density applications.  

l MT-RJ: Multi-fiber connector, allows multiple fibers to be connected simultaneously.  

Optical Couplers/Splitters:

Purpose: Divide or combine optical signals.  

Types: 

l Directional Couplers: Combine or split signals between two fibers. They can be used for various applications such as power combining, signal tapping, and wavelength division multiplexing (WDM).  

l Splitters: Divide a single input signal among multiple output fibers. Common configurations include 1x2, 1x4, 1x8, etc., where the number indicates the number of output ports.  

Optical Attenuators:

Purpose: Reduce the power of an optical signal.

Applications: 

l Power leveling in optical systems.

l Protecting sensitive components from excessive optical power.

l Adjusting signal levels for optimal performance.

Optical Isolators:

Purpose: Allow light to pass in only one direction, preventing reflections that can interfere with signal transmission.  

Applications: 

l Laser systems to protect the laser source from backreflections.

l Fiber optic gyroscopes.  

Optical Circulators:

Purpose: Direct light in a specific sequence between three or more ports.

Applications: 

l WDM systems.  

l Fiber optic sensing.