  Multimode fibers are widely explored for optical communication, imaging and
sensing applications. The interference of fiber guided modes generates a
speckle pattern, which has been used for high-precision spectroscopy,
temperature, and strain sensing. Here we demonstrate a single-shot full-field
temporal measurement technique based on a multimode fiber. The complex
spatiotemporal speckle field is created by a reference pulse propagating
through the fiber, and it interferes with a signal pulse. From the
time-integrated interference pattern, both the amplitude and the phase of the
signal are retrieved in spectral and temporal domains. The simplicity and high
sensitivity of our scheme illustrate the potential of multimode fibers as
versatile and multi-functional sensors.
