Ocean bottom fibre optic seismic sensing system

An array of seismic sensor stations 100A comprises a plurality of array cables each comprising a series of array cable modules 140 and a multi-fibre lead cable 141, each array cable module 140 comprises a series of seismic sensor stations 142 connected by the lead cable, each sensor station houses a plurality of optical sensors, and all stations within the same array cable module share a common sensor fibre 146. For each array cable module a module connection node 144 couples a different one of the fibres of the multi-fibre lead cable 141 to the common sensor fibre 146 used to interrogate a series of seismic sensor stations. The plurality of optical sensors in each sensor station 142 share a common wavelength which is different for each station in a module. Time division multiplexing and wavelength division multiplexing are used to interrogate the sensors in each station.