A white Light interferometer, used e.g. in the context of low-coherence interferometry, is an interferometer, typically a Michelson interferometer, which works with a white light source, i.e., with a Light Source with broad optical bandwidth.
The light Source is not necessarily operating in the visible spectral range, really generating white light. Its temporalCoherence has to be rather small, while a high spatial coherence is normally needed. The high spatial coherence combined with a broad Bandwidth can most easily be obtained by launching light from a bulb into a single-mode fiber, but this leads to a very small launched power. The brightness can be increased by many orders of magnitude by using a superluminescent source such as e.g. a superluminescent diode. In some cases, wavelength-swept Tunable Lasers are used.