  We briefly report our recent progress on the study of the polarized
fragmentation functions of $\Lambda$ hyperon in unpolarized semi-inclusive
deep-inelastic scatterings and electron-positron annihilations at low energies.
In particular, we present a simple but practical method on how to measure the
azimuthal-angle-dependent longitudinal polarization and the transverse
polarization inside the production plane and bridge these observables to the
corresponding structure functions and fragmentation functions at the leading
twist. Our work diversifies the high energy reactions that can probe the
polarized fragmentation functions.
