Recently, mode division multiplexing (MDM) has been introduced into optical transmission systems and networks for capacity enhancement. In this letter, we propose a bidirectional passive optical network (PON) architecture based on MDM. The bidirectional optical distribution network of the MDM-PON consists of few-mode fiber, passive mode multiplexer/demultiplexer, and few-mode circulators, all of which are characterized by low modal-crosstalk. Signals in different modes are able to be transmitted and received independently for both downstream and upstream transmission. We experimentally demonstrate the bidirectional MDM-PON transmission over 10-km two-mode optical fiber. The 10-Gb/s ON-OFF-keying signals can be independently transmitted and directly detected without coherent receiver and multiple-input multiple-output processing. Moreover, nonlinear transmission impairments are experimentally investigated.