Single-frequency fiber amplifiers are promising candidates to fulfill the challenging requirements regarding laser sources in the next generation of interferometric gravitational wave detectors (GWD) [1]. High optical output power levels up to 1 kW are required to increase the sensitivity of such GWDs. For the realization of such high output power, fiber amplifiers with large mode field areas (LMA) are required due to stimulated Brillouin scattering. However, larger core diameters also result in guided higher order modes. For this reason Chirally-Coupled-Core (3C) fibers have been developed, where additional sidecores decouple higher modes via phase matching and evanescent field coupling.