Trench assisted multi-core optical fiber with reduced crosstalk

A multi-core optical fiber, comprising:

• a plurality of cores extending parallelly along a central axis of the multicore optical fiber, wherein each core of the plurality of cores is up-doped with an up-dopant, wherein each core of the plurality of cores has an associated core relative refractive index RRI, wherein the core RRI of the plurality of cores is equal;
• a plurality of buffer layers, wherein each buffer layer of the plurality of buffer layers envelops a corresponding core of the plurality of cores;
• and
• a plurality of trench layers, wherein each trench layer of the plurality of trench layers envelops a corresponding buffer layer of the plurality of buffer layers,
• wherein each trench layer of the plurality of trench layers is down-doped with a down-dopant
• wherein each trench layer of the plurality of trench layers has a trench relative refractive index (RRI) in a range of −0.1% to −0.25%, wherein the multicore optical fiber has a cable cut-off of less than or equal to 1260 nm.