Active and Passive Mode-Locked Fiber Lasers for High-Speed High-Resolution Photonic Analog-to-Digital Conversion

We present a complete set of mode-locked fiber lasers designed for photonic analog-to-digital conversion. Design, simulation, fabrication, and characterization of Er-doped fiber lasers are carried out through optimizing their performance to suit the requirements of high-speed and high-resolution photonic-assisted analog-to-digital converters. The required properties are achieved by active mode-locking on the basis of amplitude modulation of the cavity losses through a Mach–Zehnder modulator, and passive mode-locking on the basis of fast semiconductor saturable absorbers and intracavity polarizing fibers. The use of an intracavity polarizing fiber in combination with a fast saturable absorber allows dynamic control of the operation regimes through polarization control. Besides these oscillators designed with ring cavity structure, a short linear cavity with fundamental repetition frequency at the order of 1 GHz is studied, and an effective continuous tunability of the repetition frequency is obtained by an electromechanical transducer. Pulsed repetition rates up to 20 GHz, pulsewidths down to 500 fs, and time jitters below 180 fs are obtained. Fiber lasers based on standard and commercially available telecom devices are demonstrated to be a low-cost, compact, and versatile optical source for photonic-assisted analog-to-digital conversion.