Overview of the GRAVITY chain of single-mode waveguides. The light coming from the telescopes is injected in the Fiber Coupler fibers inside the cryostat of GRAVTY (first section). Each fiber is then connected to a FDDL (Sect. 2) and to a Fibered Polarization Rotator (Sect. 3). The light is then fed to the V-groove fibers connected to the integrated optics beam combiner (Sect. 4 inside the dash-dotted line box). All work at cold temperatures (240 K for the first three sections and 200 K for the integrated optics beam combiner part). This figure was first presented in Perraut et al. (2018).