A planar waveguide Nd:YAG laser is pumped with 430 W of power from 10 laser diode bars to produce a multimode output power of 150 W at an optical efficiency of 35%. Use of a hybrid resonator of the positive-branch confocal unstable type for the lateral axis and of one of the near–case I waveguide type for the transverse axis increased the laser brightness by a factor of $\sim 26$ with only 12% less power than in the multimode case.

In this paper we describe a unique and innovative pipeline and flowline monitoring system which has been developed by Schlumberger in collaboration with BP. Applications of the system include pipeline/flowline integrity monitoring and overall optimization of the operation of the pipeline/flowline. Details of the pipeline condition monitoring system (PCMS) components are provided along with the results from comprehensive field trials. The system uses novel optical fibre distributed sensors to provide simultaneous distributed measurements of temperature, strain and vibration for the detection, monitoring, and location of events including: • Third Party Interference (TPI), including multiple simultaneous disturbances; • Geo-hazards and landslides; • Gas and oil leaks; • Permafrost protection. The system performs analysis of the combination of measurands to provide the operator with an event recognition and location capability allowing the most appropriate early response to be initiated. Through the use of newly developed remote, optically powered amplification, an unprecedented detection range of 100km is achieved without the need for any electronics and therefore remote power in the field. A system can thus monitor 200km when configured to monitor 100km in two directions from a single location. As well as detecting the external conditions leading to leaks, this fully integrated system provides a means of detecting and locating small leaks in gas pipelines below the threshold of present online leak detection systems based on monitoring flow parameters. Other benefits include the enhancement of the operator’s existing integrity management program and the potential for reductions in surveillance costs and HSE risks. In addition to onshore pipeline systems this combination of functionality and range is available for practicable monitoring in a wide range of other applications such as: • Long subsea flowlines; • Umbilicals; • Power cables; • Offshore riser systems; • Settlement in tank farms; • Facilities perimeter security. An important deliverable from this work includes the design and field testing of a bespoke optical sensor cable, designed to be sensitive to ground movement to allow distributed strain measurement whilst withstanding the rigors of the pipeline environment. In this paper, we describe the new optical sensing methods developed, and the results of the extensive field trials performed during 2007 and 2008 to fully evaluate and prove the system for use on long hydrocarbon transmission pipelines. Specifically, we demonstrate the detection of small gas releases, simulated earth movement and a number of different types of third party interventions at the full 100km target range.

Distributed acoustic sensing (DAS) is a highly effective method of monitoring all kinds of intrusions on railway tracks. These intrusions represent a real problem in the railway sector, as they can lead to human deaths or damage to railway tracks, and these intrusions may be human or animal. A fiber was deployed along 12 km of track in a railway test center, enabling us to acquire data day and night. A data acquisition campaign was carried out in April 2023 to capture the signatures of several scenarios (walking, digging, falling rocks, etc.) in order to train machine learning models and prevent any intrusion by detecting and classify these intrusion. The study shows the diversity of signals that fiber can acquire in the rail sector and the machine learning model performance. Signals associated with the presence of animals are also presented.

We report the enhanced performance of distributed Brillouin fiber optic sensor using two stages of remotely pumped erbium-doped fiber combined with Raman amplification. Intensity and frequency resolutions of 0.60% and 0.30MHz were achieved at 100km.