Generation of a 64-GHz, 33-ps transform-limited pulse train from a fiber laser employing higher-order frequency-modulated mode locking

We demonstrate the generation of optical pulses at a repetition rate of 64 GHz directly from a frequency-modulated (FM) mode-locked fiber laser. This is achieved by phase modulation at 16 GHz and by initiating of higher-order FM mode locking by use of an intracavity Fabry-Perot filter with a free spectral range of 64 GHz. This process yielded transform-limited pulses with a width of 3.3 ps. We investigated the operating characteristics of the laser and compared them with the characteristics that were predicted theoretically.