Wide-band dual-mode operation of multi-core fibers with air-hole structure

• Unique characteristic of strict dual-mode operation (HE11 mode and HE21 mode only).
• The number of LP11 modes is decreased to half so as to reduce the mode coupling.
• It is a breakthrough in enlarging the effective area.
• It exceeds the trade-off between bending loss and effective area.

A novel multi-core dual-mode fiber consisting of 11 cores with eight air holes for wide-band dual-mode operation is proposed in this paper. Modal properties, operation range and effective area affected by core-to-core distance, core-to-pitch ratio, relative index difference and center core diameter are investigated systematically. For 11-core dual-mode fiber with air-hole structure, simulation shows that it can support both a strict dual-mode operation (propagation in HE11 mode and HE21 mode only) and low bending losses (less than 0.8 dB/m at R>0.20 m), meanwhile maintaining a large effective area up to 1120.33 μm2. With a proper design of structural parameters the effective area of the 11-core dual-mode could be even higher. It has great advantages over conventional few-mode fibers, multi-core fibers and step-index single-mode fibers in terms of less mode coupling, larger effective area and lower bending loss.