All-Optical Subsea Sensing and Communications

Subsea control systems utilize electric and/or optical communication channels within subsea optical distribution systems for redundant, duplex telemetry between topside facilities and subsea control systems. Downhole fiber optic sensing (DFOS) systems utilize the same subsea optical distribution systems for establishing transmission paths between the same topside facilities and downhole sensing fibers. To date, subsea fiber optic control and sensing systems have been operated on independent subsea optical distribution systems. This redundancy introduces complexity and cost into the overall subsea optical distribution system required for subsea developments. We describe the systems that combine fiber optic communications for subsea control systems and downhole fiber optic sensing systems into the same subsea optical distribution system. This enables simultaneous operation of communications between the topsides and subsea control module, and the topside interrogation of multiple downhole fiber optic sensors while preserving dry-tree equivalent sensing performance.