Uncoupled multicore optical fiber with alkali doped, off-set trench cores

An uncoupled core multicore optical fiber, comprising:

• 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 comprises:
• a central axis,
• a core region extending from the central axis to an outer radius r1, the core region comprising a relative refractive index Δ1 relative to pure silica, wherein each of the at least two core portions is doped with a dopant from a group comprising 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, the inner cladding region comprising a relative refractive index Δ2 relative to pure silica,
• 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 comprising a relative refractive index Δ3 relative to pure silica and having a trench volume greater than or equal to 20% Δ micron2 and less than or equal to 60% Δ micron2,
• the common cladding region encircling and directly contacting the trench region and extending from the outer radius r3 to the outer radius RCC and
• wherein the cable cutoff of each core portion is less than 1530 nm, wherein an effective area of each core portion is greater than or equal to 105 μm2 and less than or equal to 135 μm2 at a wavelength of 1550 nm and wherein the central axes of the at least two core portions are separated from one another by a minimum separation distance that is greater than or equal to 45 microns and less than or equal to 60 microns.