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

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 mu m(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.