A PLC splitter uses a silica-based planar lightwave circuit chip with integrated waveguides to evenly divide a single optical input into multiple outputs.

Internal Structure

Inside a PLC splitter, the core component is a planar lightwave circuit (PLC) chip made of silica glass. This chip contains optical waveguides etched onto a flat substrate using photolithography and semiconductor-like fabrication techniques . The waveguides guide light from the input fiber through a network of branching paths, ensuring precise and uniform distribution to multiple output fibers . The chip is typically housed in a compact module that protects it from environmental factors and maximizes optical coupling efficiency .

Working Principle

1. Input Coupling: The optical signal enters the splitter through an input fiber and is coupled into the input waveguide on the PLC chip .
2. Propagation: Light travels through the waveguides via total internal reflection, maintaining signal integrity .
3. Splitting: The waveguides branch out in Y-shaped or cross-shaped patterns, dividing the optical power equally or according to a specified split ratio (e.g., 1×2, 1×4, 1×8, up to 1×64), . Each Y-branch splits the light into two paths, and this process is repeated in cascaded stages to achieve the desired number of outputs .
4. Output Coupling: The divided signals exit through output fibers, each carrying a portion of the original signal. The slight reduction in power, known as insertion loss, is consistent across outputs due to the precise waveguide design .

Fabrication Process

PLC splitters are manufactured using techniques adapted from semiconductor production :

• Silica Deposition: Layers of substrate and cladding are built using flame hydrolysis deposition.
• Photomask Printing: The circuit layout is transferred to a chromium glass mask.
• Photoresist Application and UV Exposure: A light-sensitive polymer is applied and patterned with ultraviolet light to define the waveguides.
• Etching and Assembly: The waveguides are etched, and the chip is integrated with input/output fiber arrays and protective housing.

Applications

PLC splitters are widely used in Passive Optical Networks (PON), FTTx deployments, and 5G front-haul networks. They allow a single fiber from a central office or distribution hub to serve multiple endpoints reliably without requiring power . Their compact size, high reliability, and uniform signal distribution make them ideal for both centralized and distributed network architectures . In summary, the PLC splitter's internal design combines precision waveguides, Y-branch splitting, and robust packaging to efficiently distribute optical signals across multiple outputs while maintaining consistent performance.