Sensor system with time division multiplexing telemetry

Abstract

A seismic array containing a large number of seismic sensors, which may be optical hydrophones, has successive sections, each of which contains a subarray of sensor channels, interconnected by a fiber optic signal transmission line via telemetry modules. Synchronizing signals for initiating successive scans of the sensors in the array and timing the multiplexing of the channels are transmitted along the signal transmission line from the tail end of the line through telemetry modules to the head end. Equipment for receiving, demultiplexing and processing the seismic data is provided at the head end. The array may be towed as a seismic streamer and the head end equipment located topside on the towing vessel. The telemetry modules provide hybrid optical/electrical operation such that array sections including the optical hydrophones and fiber optic links are coupled to each other exclusively by electrical connectors. Submultiplexing of each subarray of sensors (hydrophones) is carried out by the telemetry module under control of scan synchronizing and timing signals so as to avoid the need for anti-aliasing filters and sample and hold circuits associated with the hydrophones in the array, while improving the signal to noise ratio of the seismic data signals derived from the array, in spite of shot or photon noise and also minimizing timing skew errors.