[en] Electromagnetic and nuclear breakup of the neutron-rich oxygen isotopes ranging from A=17 to A=22 is studied experimentally in reactions at energies around 600 MeV/u. The beams were produced in fragmentation reactions and separated by the GSI fragment separator FRS. By measuring the four-momenta of all decay products after inelastic scattering and neutron decay of the projectile, the excitation energy is determined. From the differential cross sections dσ/dE^* for electromagnetic excitation, the E1-strength distributions can be deduced. For ^18,20,22O, low-lying dipole strength is observed, exhausting about 5% of the Thomas Reiche Kuhn sum rule for energies up to 5 MeV above the continuum threshold. (orig.)