  A thermal ghost imaging scheme between two distant parties is proposed and
experimentally demonstrated over long-distance optical fibers. In the scheme,
the weak thermal light is split into two paths. Photons in one path are
spatially diffused according to their frequencies by a spatial dispersion
component, then illuminate the object and record its spatial transmission
information. Photons in the other path are temporally diffused by a temporal
dispersion component. By the coincidence measurement between photons of two
paths, the object can be imaged in a way of ghost imaging, based on the
frequency correlation between photons in the two paths. In the experiment, the
weak thermal light source is prepared by the spontaneous four-wave mixing in a
silicon waveguide. The temporal dispersion is introduced by single mode fibers
of 50 km, which also could be looked as a fiber link. Experimental results show
that this scheme can be realized over long-distance optical fibers.
