  Distributed Acoustic Sensing (DAS) has become a popular method of observing
seismic wavefields: backscattered pulses of light reveal strains or
strain-rates at any location along a fiber-optic cable. In contrast, a few
newer systems transmit light through a cable and collect integrated phase
delays over the entire cable, such as the Microwave Frequency Fiber
Interferometer (MFFI). These integrated systems can be deployed over
significantly longer distances, may be used in conjunction with live
telecommunications, and can be significantly cheaper. However, they provide
only a single time series representing strain over the entire length of fiber.
This work discusses theoretically how a distributed and integrated system can
be quantitatively compared, and we note that the sensitivity depends strongly
on points of curvature. Importantly, this work presents the first results of a
quantitative, head-to-head comparison of a DAS and the integrated MFFI system
using pre-existing telecommunications fibers in Athens, Greece.
