“…With the use of semiconductor optical amplifiers [18][19][20], Mach-Zehnder interferometers [21][22][23], ring waveguides and resonators [24,25], and nonlinearly birefringent fibers [26][27][28][29][30], different kinds of OOK-to-PSK and NRZ-to-RZ format convertors were proposed and comprehensively investigated in past decades. To upgrade the OTDM transmission up to 40 Gbit∕s or higher, the external encoding of a continuouswave (CW) laser with a nonlinearly biased modulator [31,32], or the NRZ-to-RZ in versatile photonic devices [33][34][35][36], were also proposed. The synthesizer-free pulsed RZ signal and clock with ultralow jitter at high repetition rate extracted [37,38] or generated [39,40] from versatile sources, especially those demonstrated with the assistance of self-starting optoelectronic oscillators (OEOs), have emerged as novel optical carriers for high-bit-rate OTDM communications.…”