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Photonic Crystal Fibers - PCF

The concept of microstructured fibers (also called PCF: Photonic Crystal Fibers) opens up a wide ranged flexibility to introduce specific functionalities in light guiding properties.

The advantages of PCF relative to conventionally doped fibers are:

  • flexible structural parameters (e.g. air fraction, pitch L of air holes) allows to prepare fibers with unusual optical behavior (endlessly single mode propagation, extreme dispersion behavior)
  • the light propagation mechanisms can be either index guided or band gap guided
  • the change of glass materials beyond pure silica allows to tailor microstructured fibers with excellent properties for special applications (e.g. holey Bragg grating fibers, special sensor fibers, fibers for non-linear applications)
Principles of light guiding by optical fibers:
Principles of light guiding by optical fibers:
(a) SMF – standard single mode fiber
(germanium doped core)
(b) Index guiding PCF
(c) Photonic band gap fiber
Geometrical parameters: d – hole diameter, Λ – pitch, D – core diameter

Preparation of microstructured fibers

We prepare microstructured fibers by “stack-and–draw” technology from preforms of high silica and other special glasses. We manufacture them by elongation of glass rods and tubes at the fiber drawing device. The microstructured design is prepared from holey capillary packages and/or filament arrangements composed of different material modified rod assemblies.

A main challenge is the transfer of the excellent properties of silica-based photonic crystal fibers, like low spectral loss or good durability, to the modified or non-silica materials. The preparation of modified silica-based photonic crystal fibers was implemented by the MCVD doping process.

Microstructured optical fibers
Microstructured optical fibers

The technological basis for manufacturing is the difference pressure drawing process: Low pressure inside the overcladding tube implies a subsidence of pressure from 200 Pa to 2500 Pa relative to ambient pressure. The adjusted overpressure is based on the actual capillary dimensions and compensates the collapsing effect.

Schematical diagram of preparation of microstructured fibers by difference pressure processing
Schematical diagram of preparation of microstructured fibers by difference pressure processing
IPHT Jena

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