  Using 1.0 fb^{-1} of pp collision data collected at a centre-of-mass energy
of sqrt{s}=7 TeV with the LHCb detector, measurements of the polarization
amplitudes, strong phase difference and triple product asymmetries in the B_s^0
-> phi phi decay mode are presented. The measured values are |A_0|^2 = 0.365 +-
0.022 (stat) +- 0.012 (syst), |A_perp|^2 = 0.291 +- 0.024 (stat) +- 0.010
(syst), cos(delta_parallel) = -0.844 +- 0.068 (stat) +- 0.029 (syst), A_U =
-0.055 +- 0.036 (stat) +- 0.018 (syst), A_V = 0.010 +- 0.036 (stat) +- 0.018
(syst) .
