This paper provides theoretical analysis of existing optical distribution network (ODN) that integrates mobile backhaul network with already existing passive optical network (PON). The need to reduce the cost of laying down new fibres for mobile backhaul networks drives the need for such an integrated architecture that allows sharing of ODN. In this paper, analysis has been done for the two arms of architecture, i.e. the mobile backhaul system and passive optical network arm. A wavelength division multiplexing (WDM) combiner is used to stream data from the two arms of the architecture. The PON ODN is considered to have 10 Gbps data rate downstream and 2.5 Gbps rate upstream and a bit error rate (BER) less than 10T9. The power budget analysis is used in both arms to determine the maximum reach possible. Rise time analysis in PON arm makes sure that the rise time stays within limits for DS and US. Delay analysis for mobile backhaul is done to make sure that the end to end delay in mobile backhaul is not more than 1 ins so as to meet 5G specifications. The analysis shows that a distance of 20 km is possible for carrying 5G mobile backhaul traffic in the existing ODN.