A Weakly-Coupled Few-Mode Hybrid Clad Photonic Crystal Fiber With Ultra-Flattened Dispersion and Low Confinement Loss

We propose a weakly-coupled ultra-flattened chromatic dispersion few-mode photonic crystal fiber (FM-PCF) supporting 10 vector modes (HE
_11a
, HE
_11b
, TM
₀₁
, HE
_21a
, HE
_21b
, TE
₀₁
, HE
_31a
, HE
_31b
, EH
_11a
, EH
_11b
) which works over a large range of wavelength across the C+L band. We investigate the chromatic dispersion, minimum effective refractive index difference (minΔn
_eff
), confinement loss, bending loss and differential mode delay (DMD) of the proposed fiber under the influences of design parameters by using the finite element method (FEM). The circular holes in the first ring are replaced by elliptical holes to obtain flattened-chromatic dispersion. And an extra small rectangular defected hole is introduced in the fiber core order to achieve ultra-flattened chromatic dispersion and large minΔn
_eff
. The simulated results show that the designed weakly-coupled FM-PCF can obtain ultra-flattened (dispersion slope < 1.8 × 10
⁻⁴
ns/km/nm
²
) and large minΔn
_eff
(> 1.6 × 10
⁻⁴
) in the wavelength range of 1520 nm to 1640 nm. And the proposed weakly-coupled FM-PCF also has ultra-low confinement loss (<10
⁻⁹
dB/km) and good bending resistance. In summary, the proposed weakly-coupled FM-PCF has the potential applications for large-capacity MDM communication systems.