Fiber link stabilization with a multicore fiber amplifier

We study the use of separate cores of a multicore erbium-doped fiber amplifier (MC-EDFA) in a noise-canceled link for ultrastable optical frequency transfer. We demonstrate fractional frequency instability of 5×10 −19 at 1000 s averaging time for the stabilized MC-EDFA alone and 1.4×10 −18 at 1000 s averaging time when integrated with a 40-km-long 7-core spooled fiber. This study further establishes multicore fiber (MCF) networks as a promising platform for ultrastable frequency transfer, serving as an important step toward incorporating precision time and frequency distribution into future MCF communication infrastructures.