  We demonstrate the implementation of a fiber-integrated spectrograph
utilizing chromatic group velocity dispersion (GVD) in a single mode fiber. By
means of GVD we stretch an ultrafast pulse in time in order to spectrally
resolve single photons in the time domain, detected by single photon counting
modules with very accurate temporal resolution. As a result, the spectrum of a
very weak pulse is recovered from a precise time measurement with high signal
to noise ratio. We demonstrate the potential of our technique by applying our
scheme to analyzing the joint spectral intensity distribution of a parametric
downconversion source at telecommunication wavelength.
