Googled this - "optical fiber as sensors for measurement strain" yesterday and happened upon this: **broken link removed**.
Sort of a standing wave concept. Sort of. Reflectometry more accurately.
Anyway, it's the use of fibre optics in a very clever fashion and over remarkable distances if need be (>100km) to measure strain, temp, etc..
Knowing no more than I do, it strikes me that it is a system that makes use of very inexpensive sensors (the fibre optics, often those already in place for data transmission) but to detect the signals generated takes some very expensive hardware and software arrangements (often proprietary) to make sense of them.
And if desired, dedicated optics utilizing Fiber Bragg Grating increase the sensitivity and reduce the effect of electrical noise to zero.