  Optical phase measurement is critical for many applications and traditional
approaches often suffer from mechanical instability, temporal latency, and
computational complexity. In this paper, we describe compact phase sensor
arrays based on integrated photonics, which enable accurate and scalable
reference-free phase sensing in a few measurement steps. This is achieved by
connecting multiple two-port phase sensors into a graph to measure relative
phases between neighboring and distant spatial locations. We propose an
efficient post-processing algorithm, as well as circuit design rules to reduce
random and biased error accumulations. We demonstrate the effectiveness of our
system in both simulations and experiments with photonic integrated circuits.
The proposed system measures the optical phase directly without the need for
external references or spatial light modulators, thus providing significant
benefits for applications including microscope imaging and optical phased
arrays.
