We observe polarization-locked vector solitons in a mode-locked fiber laser
. Temporal vector solitons have components along both birefringent axes. De
spite different phase velocities due to linear birefringence, the relative
phase of the components is locked at +/-pi/2. The value of +/-pi/2 and comp
onent magnitudes agree with a simple analysis of the Kerr nonlinearity. The
se fragile phase-locked vector solitons have been the subject of much theor
etical conjecture, but have previously eluded experimental observation.