Orthogonal Time Division Multiplexing (OTDM) and advanced modulation formats represents the future in development of high speeds communications. In this text the feasibility of OTDM systems combining multilevel modulation is studied. The report is focused in Differential Quadrature Shift Keying (DQPSK) modulation. Computer simulations study the performance of an OTDM systems using DQPSK modulation at 1.28 Tb/s and a 640Gb/s OTDM system combined with DPSK modulation. Two solutions for channel demultiplexing are shown: Nonlinear Optical Mirror (NOLM) and Four Wave Mixing (FWM). These techniques need an optical control signal. Optimums values for set the signals and for the bandwidth of the filter are evaluated. Furthermore numerical simulations are performed to evaluate the transmission performances of a 1.28Tb/s OTDM-DQPSK system and a transmission through 561.6km is demonstrated.