A fiber optic coupler belongs to the category of optical devices, specifically passive or active fiber-optic components used to split, combine, or distribute light between multiple fibers.

Overview

A fiber optic coupler is an optical device that connects multiple fiber ends, allowing light from one input fiber to be distributed to two or more output fibers, or combining light from multiple inputs into a single output fiber . Unlike connectors, which simply join fibers, couplers actively manage the distribution of optical signals and are essential in network architectures such as bus, star, or passive optical networks (PONs), .

Classification by Function

• Passive Couplers: Operate without external power, simply redirecting or splitting light using fused fibers, micro-lenses, beam splitters, or planar waveguides . Examples include splitters, combiners, X-couplers, Y-couplers, T-couplers, and star couplers .
• Active Couplers: Require external power and may include optical-to-electrical conversion, amplification, or signal processing to manage light distribution .

Classification by Fabrication

• Fused Tapered Couplers: Two or more fibers are thermally fused and tapered to allow light transfer between cores .
• Planar Lightwave Circuits (PLC): Use semiconductor substrates to create waveguides for high port-count couplers, such as 1×12 or 1×24 splitters .
• Micro-Optics Couplers: Employ prisms, lenses, or mirrors to split or combine light .

Classification by Network Topology

• Y Coupler: Splits one input into two outputs.
• T Coupler: Connects a series of nodes to a backbone cable.
• X Coupler: Combines and splits signals in a 2×2 configuration.
• Star Coupler: Distributes signals from multiple inputs to multiple outputs.
• Tree Coupler: Used in cascaded PON architectures .

Summary

In essence, fiber optic couplers are categorized as optical devices within fiber optic systems, primarily functioning as passive or active components that split, combine, or distribute light. They are further classified by fabrication method (fused, planar, micro-optics) and by network topology (Y, T, X, star, tree), making them versatile components in modern optical networks .