A suitable decoding technique for spectral amplitude coding optical code division multiple access (SAC-OCDMA)-based secured distributed vibration sensor is investigated. The study is carried out to identify the most appropriate techniques for receiving the transmitted vibration signal in SAC-OCDMA-based system. The techniques which are direct decoding, complementary and logical AND decoding are compared based on the level of crosstalk, number of components used and supported transmission distance in multiplexed vibration sensing using both simulation and experiment. The results show direct decoding capable of supporting 55 km unlike the other two which are 44 and 38 km, respectively. Aside that, direct decoding techniques could be implemented with less number of components and has optimal signal-to-noise ratio while still preventing the system again the ‘man in the middle’ attack.