Quantum ghost imaging (QGI) [1] has attracted much attention in last two decades due to its abundance in physics and potential on quantum communication and quantum sensing. Traditional QGI cannot be realized over optical fibers since photons are confined in a specific fiber mode, which cannot support the momentum-momentum correlation required in QGI. We propose and demonstrate a scheme realizing long distance QGI over optical fibers, based on the frequency entangled two-photon state  nonlinear waveguide, where s and i denote the signal and idler photons,  is the spectra density of the two-photon state. The signal and idler photons are sent to Alice and Bob, respectively. At Alice side, the signal photons are transmitted to different directions in free space by a spatial dispersion component according to their frequencies, getting to different positions at the object. The reflected photons are collected and detected with a single photon detector (SPD), containing the reflectivity information of the object. At Bob side, the idler photons are delivered to another SPD after a temporal dispersion component, reaching the SPD at different times according to the frequencies. By this way, the signal photons illuminating the different position of the object are correlated with the arrival time of idler photons at the SPD due to the frequency entanglement. The times of single photon events at Alice side are sent to Bob through a public channel to realize coincidence measurements, from which the information of the object can be obtained. The experiment setup is shown in Fig 1. The frequency entangled photon pairs are generated by the spontaneous four wave mixing (SFWM) process in a piece of silicon waveguide pumped by a mode-locked fiber laser together with power amplifying and spectral filtering modules as shown in Fig. 1(a). The generated signal and idler photons are separated by a filter system, with spectral widths of about 16 nm for both. Through a circulator (CIR), the signal photons are spatial dispersed by a diffraction grating before illuminating the object [2] which is shown in Fig 1(b). The object is illuminated by the signal photons in a line, with a span of ~200 um and the reflected photons are collected and sent to a SPD (SPD1). The idler photons are detected after traveling through 50 km-long single mode fiber (SMF), to another SPD (SPD2). The SMF introduces a group veocity dispersion (GVD) of ~900 ps/nm, which extends the arrival time of idler photons to about 15 ns. Coincidence measurements are realized using a time correlated single photon counting module (TCSPC). The object's reflectivity pattern along the illumination line is imaged in the coincidence measurement results. By step moving the object perpendicularly to the illumination line, the two-dimensional image of the object can be obtained. The experiment results of the two dimensional QGI are shown in Fig. 1 (d). The inset figure is the pattern of the object, which has high reflectivity in the red region and low reflectivity elsewhere. The main figure is the coincidence measurement results with a moving step of 10 micrometers. The coincidence counts in each time bin are indicated by different colors. A clear image of the object is obtained in the time domain. As a summary, we have proposed and experimentally demonstrated a scheme to realize long distance QGI over 50 km-long optical fibers. It will extend the application of QGI at large geographical scale and has the potential to realize long distance secure " quantum fax machine " for its less photon property. Figure 1. The experiment setup for QGI over optical fibers. (a), Frequency-entangled photon pair source based on a silicon waveguide. (b), Optical system at Alice side. (c), Optical systems at Bob side. (d), The result of two-dimensional QGI by step moving the object.