Low cross-talk multicore optical fiber for single mode operation

A multicore optical fiber comprising:

• a common cladding;
• and
• a plurality of core portions disposed in the common cladding, each of the plurality of core portions comprising:
• a central axis;
• a core region extending from the central axis to a radius r1, the core region comprising a relative refractive index Δ1 relative to pure silica;
• an inner cladding region encircling and directly contacting the core region and extending from the radius r1 to a radius r2, the inner cladding region comprising a relative refractive index Δ2 relative to pure silica;
• and
• a depressed cladding region encircling and directly contacting the inner cladding region and extending from the radius r2 to a radius r3, the depressed cladding region comprising a relative refractive index Δ3 relative to pure silica and a minimum relative refractive index Δ3 min relative to pure silica,
• wherein:
• Δ1>Δ2>Δ3 min;
• the relative refractive index Δ3 of the entire depressed cladding region in each of the plurality of core portions is less than or equal to Δ2 such that the depressed cladding region forms a depressed-index trench in a relative refractive index profile of each core portion;
• the depressed-index trench in the relative refractive index profile of each core portion has a trench volume of greater than or equal to 30% Δ μm2 and less than or equal to 75% Δ μm2;
• the mode field diameter of each core portion is greater than or equal to 8.2 μm and less than or equal to 9.5 μm at a 1310 nm wavelength;
• and
• the zero dispersion wavelength of each core portion is greater than or equal to 1300 nm and less than or equal to 1324 nm.