Solutions for Modal Squeeze in Dual-Concentric Core Photonic Crystal Fibers

Dual-concentric core photonic crystal fibers (DCC-PCF) were a kind of dispersion compensating fiber with ultrahigh negative dispersion. However, they usually have an undesirable characteristic, called “modal squeeze” in this letter, which causes difficulty in achieving a single-mode operation. This letter discusses a phenomenon of modal squeeze, and proposes a solution to avoid it. Finally, we give designing examples of DCC-PCFs for avoiding the modal squeeze and operating in single mode.