FTIR spectra of bismuth family of superconductors are studied. Polycrystalline samples of bismuth superconductors are prepared choosing an off-stoichiometric composition for phase stabilisation and reproducibility. Vibrational modes are strongly affected by the holes introduced into the CuO planes. Mid IR spectra of the Bismuth system was recorded using Bruker IFS 66v and the high frequency oxygen vibrations of the system is discussed based on the factor group analysis for both symmorphic and non-symmorphic space groups 14/mmm, F-mmm and A(maa) of different structures based on the modulated superstructure.