Bend-resistant low bending loss and large mode area single-mode fiber with low NA

Abstract

• We have designed a novel low bending loss and large mode area single-mode fiber with low NA. The proposed fiber can provide high leakage loss ratio (776) between the high-order modes (HOMs) and fundamental mode (FM). • The bending loss of FM and HOMs as function of number of trenches is researched in the paper. The bending loss and effective mode area will decrease as number of trench increase. Without ring and trench in core and cladding, the bending loss of FM and HOM are small and that cannot realize the single-mode operation. Loss ratio is smallest in all of fibers. • The HOMs suppression is better than the traditional step-index fibers (SIF). Furthermore, bending loss can be reduced to about 0.0074 dB/m which is lower than previous study. Effective mode area can achieve 744.49 μm 2 at 15 cm bending radius. This fiber design shows great potential in developing compact high-power fiber lasers and amplifiers. A novel design of trench in cladding with resonant ring is proposed in this paper. Performances of proposed fiber have been numerically investigated by the finite element method with a perfectly matched layer boundary. Simulation shows that the proposed fiber can provide high leakage loss ratio (776) between the high-order modes (HOMs) and fundamental mode (FM) which is beneficial to realize robust single-mode operation to enhance the transverse mode instabilities at a wavelength of 1080 nm. The HOMs suppression is better than the traditional step-index fibers (SIF). Furthermore, the bending loss can be reduced to about 0.0074 dB/m due to the trench in the cladding, and the effective mode area can achieve 744.49 μm 2 at 15 cm bend radius, which is also beneficial to improve transmission efficiency. The advantage of an all-solid structure along with a much simpler fabrication process makes our approach very suitable for realizing very large mode area fibers for high power fiber laser application.