1×4 Fiber Coupler Operating Principle, Definition, Core Features, and Applications

I. Definition

1×4 fiber coupler is a passive optical device that can distribute a single input optical signal to four output optical fibers in a specific ratio, or conversely, combine four input optical signals into a single output. As a key branching device in optical communication networks, it implements power distribution and routing for optical signals.

II. Operating Principle

1. Fused Taper Technology (Mainstream Solution)

Manufacturing Process: Four optical fibers are tightly arranged side by side, melted at high temperature, and then stretched to form a tapered coupling region.

Coupling Mechanism: Based on the principle of evanescent wave coupling, when the core spacing is sufficiently small, the optical fields interpenetrate.

Power Distribution: The length of the coupling region and the degree of stretching determine the splitting ratio (e.g., 25:25:25 for equal power distribution).

2. Planar Lightwave Technology (PLC)

Y-shaped branched waveguide structure is fabricated on a silicon substrate using semiconductor processing. 1×4 beam splitting is achieved by cascading multiple 1×2 beam splitters.

III. Core Features

Special Advantages:

Passive operation (no power required)

Resistant to electromagnetic interference

Compact size (typically < Φ3 mm × 60 mm)

IV. Applications

1. Fiber Optic Communication Systems

PON Networks: Connecting the OLT to four ONUs in GPON/EPON

FTTH Deployment: A single optical splitter serves four households

Optical Line Monitoring: Branching out test signals (e.g., OTDR testing)

2. Sensor Networks

Signal Distribution for Distributed Fiber Optic Sensing Systems

Applications for Temperature/Strain Monitoring (e.g., oil wells, bridges)

3. Test and Measurement

Building a Multi-Channel Optical Power Monitoring System

Parallel Optical Path Construction for Optical Experiments

4. Special Application Scenarios

Quantum Communication: Photon Distribution Systems

Medical Lasers: Multi-Path Laser Transmission