  We study the coherence properties of a trapped two-component gas of fermionic
atoms below the BCS critical temperature. We propose an optical method to
investigate the Cooper-pair coherence across different regions of the
superfluid. Near-resonant laser light is used to induce transitions between the
two coupled hyperfine states. The beam is split so that it probes two spatially
separate regions of the gas. Absorption of the light in this interferometric
scheme depends on the Cooper-pair coherence between the two regions.
