  The Palomar Fiber Nuller (PFN) is a rotating-baseline nulling interferometer
that enables high-accuracy near-infrared (NIR) nulling observations with full
azimuth coverage. To achieve NIR null-depth accuracies of several x 10-4, the
PFN uses a common-mode optical system to provide a high degree of symmetry,
single-mode-fiber beam combination to reduce sensitivity to pointing and
wavefront errors, extreme adaptive optics to stabilize the fiber coupling and
the cross-aperture fringe phase, rapid signal calibration and camera readout to
minimize temporal effects, and a statistical null-depth fluctuation analysis to
relax the phase stabilization requirement. Here we describe the PFN final
design and performance, and provide a demonstration of faint-companion
detection by means of nulling-baseline rotation, as originally envisioned for
space-based nulling interferometry. Specifically, the Ks-band null-depth
rotation curve measured on the spectroscopic binary eta Peg reflects both a
secondary star 1.08 +/- 0.06 x 10-2 as bright as the primary, and a null-depth
contribution of 4.8 +/- 1.6 x 10-4 due to the size of the primary star. With a
30 mas separation at the time, eta Peg B was well inside both the telescope
diffraction-limited beam diameter (88 mas) and typical coronagraphic inner
working angles. Finally, we discuss potential improvements that can enable a
number of small-angle nulling observations on larger telescopes.
