My apologies for being unclear. I'm not trying to be difficult, just genuinely curious about the differences in sensitivities /capabilities between something like fiber optic DAS and the OTDR device you mentioned previously.

Like I discussed earlier, I am familiar with fiber optic DAS interrogators and how they can be used to detect minute changes in strain across a specific location along a fiber optic cable (using Rayleigh backscattering), but what remains a question is if other telecom related hardware (e.g., these OTDR devices that seem to be geared more towards finding line segments permanently damaged by high strain events) are sensitive enough to detect changes associated with much smaller levels of strain (that don't damage the cable)? That's the question. Like for one of these subsea cables, do they have to alter the way they send/receive signals through the fiber optic lines depending on if it is low vs. high tide? Could you hook up an OTDR device to one of these subsea fiber optic cables and (without looking at the water level) tell if it was high vs. low tide? I believe you can do this using fiber optic DAS, but I don't have experience with other telecom-specific hardware/diagnostics and if they are designed with that level of sensitivity.