Demonstration of 1 Tb/s transmission over 6.3-km 1 × 4 linear array multicore fiber with standard 125-μm cladding

•This paper explores the design of a 1 × 4 linear array multicore fiber with 125-μm cladding for O-band transmission.•Fiber design for a balanced performance between inter-core crosstalk and the tunneling loss of outer cores near the cladding edge was identified.•We demonstrated error-free 400G LR4 and 100G LWDM transmission over 6.3 km of an MCF with a total data rate of 1 Tb/s.