Several types of active fibers with a large effective mode area (LMA) have been developed for high power scaling including LMA fibers with a low-aperture core, micro-structured rod-type fiber helical core or chirally-coupled fibers, and tapered double-clad fibers (T-DCF). The mode field diameter (MFD) achieved with these low aperture technologies usually does not exceed 20–30 μm. The micro-structured rod-type fiber has much larger MFD (up to 65 μm ) and good performance. An impressive 2.2 mJ pulse energy was demonstrated by a femtosecond MOPA containing large-pitch fibers (LPF). However, the shortcoming of amplification systems with LPF is their relatively long (up to 1.2 m) unbendable rod-type fibers meaning a rather bulky and cumbersome optical scheme. LPF fabrication is highly complex requiring significant processing such as precision drilling of the fiber pre-forms.  The LPF fibers are highly sensitive to bending meaning robustness and portability is compromised.