Multi-axial integrated optics solution for POPS, a 2nd-generation VLTI fringe tracker

POPS (Planar Optical Phase Sensor) is a second-generation fringe tracker for the Very Large Telescope Inter-ferometer (VLTI), intended to simultaneously measure the cophasing and coherencing errors of up to six Unit Telescopes (UT) or Auxiliary Telescopes (AT) in real time. The most promising concepts are probably based on the utilization of Integrated Optics (IO) components, and were the scope of a Phase A study led by Observatoire de Grenoble (LAOG). Herein is described a tentative design built around a multi-axial IO chip whose fringes are dispersed downstream on a detector array, and a Chromatic Phase Diversity algorithm presented in another paper of this conference1. We depict the foreseen opto-mechanical, detection and software implementations, and provide numerical results from a realistic simulation model in terms of group and phase delay measurement accuracy and limiting magnitudes in the K band. The ultimate performance of the method is discussed and compared with the original 2nd generation VLTI fringe tracker requirements