Fiber couplers are devices used to connect two optical fibers, allowing light to pass from one fiber to another. They are essential in telecommunications and data transmission, as they help manage and direct light signals efficiently. Fiber couplers can combine or split light signals, making them versatile for various applications. These couplers come in different types, such as fusion splicers and fiber optic splitters. Fusion splicers join two fibers by melting their ends together, while fiber optic splitters divide a single input signal into multiple outputs. Both types play a crucial role in enhancing the performance of fiber optic networks.