Traditional optical fibers consist of a solid core and cladding, whereas photonic crystal fibers (PCF) are crafted with a microstructure featuring air holes, providing precise control over light guidance and characteristics. In standard optical fibers, light travels through a solid core surrounded by a cladding layer of lower refractive index, ensuring guided propagation. On the other hand, PCFs exhibit a periodic arrangement of air holes along the fiber's length, generating a photonic bandgap effect that guides light. Alternatively, if the core is solid and surrounded by air holes, light can propagate through a modified total internal reflection phenomenon.

Photonic crystal fibers function based on the same index-guiding concept as traditional optical fibers. However, they possess a significantly greater effective refractive index contrast between the core and cladding, enabling enhanced confinement and making them well-suited for utilization in nonlinear optical systems.