Core alignment for large mode area (LMA) fibers

Abstract

Large mode area (LMA) fiber types are widely used in many different fiber laser systems. Since the core diameter of an LMA fiber is generally larger than the mode field diameter (MFD), LMA fibers can carry a few higher order modes (HOM). When LMA fibers are spliced together (such as a splice of a passive LMA fiber to an active LMA fiber) if the cores are not well aligned it may result in beam shape deterioration and downstream fiber over-heating. An appropriate core alignment method for fusion splicing of LMA fiber is thus essential for the fiber laser manufacturing process, especially for multi-kW systems. A recent study on LMA fiber core alignment is reported in this paper and has been implemented in new firmware available for FSM-100 series fusion splicers.