  In this letter we experimentally validate, for the first time, the Stokes
space algorithm (SSA) equalizer for space division multiplexing (SDM)
transmission systems. We introduce the frequency domain (FD)-SSA and FD
least-mean square (FD-LMS) algorithms, and evaluate their performance for
different frequency offsets by computer simulations. Our simulations show that
FD-SSA is insensitive to the frequency offsets, not requiring carrier frequency
estimation (CFE) before equalization (pre-CFE) or carrier phase estimation
(CPE) inside the loop (L-CPE). Our experimental results confirm that FD-SSA
presents the same performance as FD-LMS, where the required digital signal
processing (DSP) stack for FD-SSA is simpler compared to the FDLMS.
