Embodiments of current disclosure include a multicore optical fiber including a common-cladding region having a refractive index Δcc and an outer radius RCC; and at least two core portions disposed within the common-cladding region, wherein each core portion includes a central axis, a core region extending from the central axis to an outer radius ri, wherein each of the at least two core portions is doped with a dopant from a group including sodium, potassium, rubidium or combination thereof, an inner-cladding region encircling and directly contacting the core region and extending from the outer radius r1 to an outer radius r2, a trench region encircling and directly contacting the inner cladding region and extending from the outer radius r2 to an outer radius r3, the trench region having a trench volume greater than or equal to 20% Δ micron2 and less than or equal to 60% Δ micron2.