An optical distribution network (ODN) sharing scheme to integrate mobile backhaul networks with the existing passive optical network (PON) systems is proposed and demonstrated. With the ODN sharing scheme, the expense of building new fibers for the next-generation fifth-generation (5G) mobile backhaul networks can be reduced. As many wavelengths are allocated to the already deployed PON systems, there remain limited wavelengths for the mobile backhaul systems. Hence, to efficiently increase the serving cell sites of the 5G systems, spectral-efficient orthogonal frequency-division multiplexing (OFDM) is adopted in the mobile backhaul systems. In order to reduce the latency of the system, adaptive adjustment of the OFDM signals for different transmission distances is averted. The OFDM signals are transmitted only using specific available bandwidth. The available bandwidth for each wavelength is studied according to the power fading relationship between the transmission distances and the chirp induced from signal modulation. A proof-of-concept demonstration experiment has been performed. In our results, 20.17 Gb/s with a bit error rate (BER) lower than 3.8 × 10 -3 was realized with a split ratio of 256 and a 40-km transmission distance of the PON ODN. Hence, each wavelength can support about 20, six, and two nodes for the IMT-advanced, current Long-Term Evolution-Advanced (LTE-A) systems, and the expected 5G systems, respectively.