“…This phase modulation is converted into amplitude modulation in the DI, which results in an RZ output signal with a controllable pulse-width (duty-cycle) determined mainly by the offset delay ( t) of the DI. Yang et al [66] used a piece of polarization maintaining fibre with a differential delay ( t), along with two polarization controllers and a polarizer to form a DI, while Zhao et al [67] used a reconfigurable Differential Group Delay (DGD) generator. Other researchers have used the same conversion scheme for multiple wavelength operations, where more than one NRZ input data sequences are converted to RZ format [68,69], as presented in Figure 2.16.…”