Oil and gas extraction pipelines generally include joints between sections of pipe and between the main pipe and bypass pipes. The flow of oil or gas within such pipes can cause vibrations within the pipes and relative movement between pipes at joints. These vibrations and movement can ultimately lead to damage or failure of the joint. It is desirable to be able to monitor the physical conditions (such as strain) experienced at pipe joints. These measurements should ideally be available in real time in order that conditions causing high loads and potential failure can be identified. Current practice within the oil and gas industries, includes monitoring pipe joints by visual inspection using remotely operated vehicles (ROVs) or using intelligent pigs travelling within the pipes themselves. These pigs can measure structural parameters such as corrosion, cracks and pipe thickness. Both ROVs and pigs can only provide intermittent measurements, and inspection using these methods is costly. Pipe joints are also monitored using electrical strain gauges, inclinometers and accelerometers located on the pipes.