We propose and demonstrate the increased dispersion tolerance with an improvement in spectral efficiency for long reach passive optical networks, with the use of polarization division multiplexing (PDM) and optical duobinary (ODB) modulation format. We investigate the stimulated Brillouin scattering threshold for data in PDM–ODB format through experiments. Improvement in power budget with PDM ODB format is demonstrated experimentally. © 2016, Springer Science+Business Media New York.