The industry has seen the gradual implementation of step-change optical sensing technology as one way to address the issue of reliable permanent downhole gauges. This paper will include case histories that indicate an ever-broadening acceptance of this technology with application scenarios ranging from simple single-gauge installations to multi-zone intelligent wells with integrated sensing and remotely activated in-well zonal flow control -true Smart or Intelligent Wells, with now over 600 installations worldwide.Present measurement capabilities include Pressure and Temperature, Distributed Temperature Sensing (DTS), Single-and Multiphase Flowmeters, Seismic Accelerometers and hydrophones, and the paper will also detail additional downhole and subsea optical sensing systems currently under development.As subsea continues to play a vital role in our industry, it has been recognized that there are a number of challenges to be addressed before optical sensing systems will be widely adopted subsea.These challenges are being addressed in part by a new thirty member company industry group, SEAFOM (Subsea Fiber-Optic Monitoring) -this group's activities will be described.In addition, a number of operating and service companies have on-going related initiatives. For example, StatoilHydro has an Integrated Operations (IO) initiative aimed at significantly increasing overall recovery rates of subsea production assets. As part of that initiative, StatoilHydro and Weatherford signed a three year Technical Development Cooperation Agreement in June 2006. This project will make real-time reservoir monitoring and downhole data available everywhere on a StatoilHydro network infrastructure. This paper includes the rationale for selecting fiber optics as the baseline technology and also describes the technical solution for an open, high speed communication infrastructure. The project is also developing interfaces towards existing subsea systems with only electrical, low bandwidth communication systems. Solutions are being developed for both Green and retrofit Brown field applications.