Photonic Crystal Fiber

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What Does Photonic Crystal Fiber Mean?

Photonic crystal fiber (PCF) is a kind of optical fiber that uses photonic crystals to form the cladding around the core of the cable. Photonic crystal is a low-loss periodic dielectric medium constructed using a periodic array of microscopic air holes that run along the entire fiber length.


In PCFs, photonic crystals with photonic band gaps are constructed to prevent light propagation in certain directions with a certain range of wavelengths. Contrary to normal fiber optics, PCFs use total internal reflection or light confinement in hollow core methods to propagate light. Light propagation in PCFs is far superior to standard fiber, which uses constant lower refractive index cladding.

Applications for photonic crystal fibers include spectroscopy, metrology, biomedicine, imaging, telecommunication, industrial machining and military technology.

Photonic crystal fiber is also known as microstructured, or holey, fiber.

Techopedia Explains Photonic Crystal Fiber

Fiber-optic cables are constructed with a core and a cladding of constant refractive index difference. Light travels through the core as a result of the refraction property of light, which occurs as a result of the difference between the refractive indexes of the core and cladding. This refracted light bears much higher loss during propagation over extended distances, and thus requires repeaters and amplifiers for extended distance communications.

In PCF, on the other hand, light is trapped in the core, providing a much better wave guide to photons than standard fiber optics. The polymers used instead of glass in PCF provide the advantage of a more flexible fiber, which allows for easier and less expensive installation. Various photonic crystals conforming to various photonic lattices are manufactured depending on the required properties of the propagated light.

Photonic crystal fibers are generally divided into two main categories:

  • Index-Guiding Fibers: Have a solid core like conventional fibers. Light is confined in this core by exploiting the modified total internal reflection mechanism.
  • Photonic Bandgap (Air Guiding) Fibers: Have periodic microstructured elements and a core of low-index material (hollow core). The core region has a lower refractive index than the surrounding photonic crystal cladding. The light is guided by a mechanism that differs from total internal reflection in that it exploits the presence of the photonic bandgap (PBG).

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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.