Design of ultra-flattened dispersion weakly coupled few-mode photonic crystal fiber with low confinement loss

Abstract

We present a unique design of weakly coupled few-mode photonic crystal fiber (FM-PCF), which can support six vector modes (HE11a,HE11b,TM01,HE21a,HE21b, and TE01) with ultra-flattened chromatic dispersion over the C wavelength band. We investigate the impact of fiber parameters on chromatic dispersion, minimum effective refractive index difference (minΔneff), confinement loss, bending loss, and differential mode delay using the finite element method. To achieve ultra-flattened chromatic dispersion and large minΔneff, an extra small elliptical defected hole is introduced in the fiber core. The circular holes in the first ring are replaced by elliptical holes to further obtain flattened-chromatic dispersion. The simulated results show that the designed weakly coupled FM-PCF can obtain an ultra-flattened average dispersion of 0.011 ns/nm/km with a small dispersion slope (<1.5 × 10 − 5 ns / km / nm2) in the wavelength range of 1520 to 1570 nm. And the proposed weakly coupled FM-PCF has large minΔneff (>1 × 10 − 3), low confinement loss (<10 − 4 dB / km), and good bending resistance. In summary, the proposed weakly coupled FM-PCF has potential applications for large-capacity MDM communication systems.