  We reveal a new class of \textit{non-degenerate} Akhmediev breather (AB)
solutions of Manakov equations that only exist in the focusing case. Based on
exact solutions, we present the existence diagram of such excitations on the
frequency-wavenumber plane. Conventional single-frequency modulation
instability leads to simultaneous excitation of three ABs with two of them
being non-degenerate.
