Aiming at the capacity limit of single-mode fiber, a 4×100 Gbit/s dual polarization quadrature phase-shift keying (DP-QPSK) interleaved long-distance quasi-single-mode bi-directional transmission is achieved when we use a few-mode fiber, and the transmission distance is over 1700 km. We also study the effects of multi-path interference (MPI) and double-Rayleigh scattering (DRS) on the system. The loss caused by MPI can be effectively compensated by the constant modulus algorithm (CMA) with 301 taps, and the performance of the system increases about 1 dB. Meanwhile, a waveform shaper is used to suppress signal degradation resulting from DRS. The results show that the transmission distance can be extended from 1400 km to 1700 km by these methods.