The C-band 40 GHz picosecond fiber laser (PSL-40-1T) is an actively mode-locked fiber laser with a repetition rate from 20 to 40 GHz that provides a stable and reliable optical clock with turnkey operation. Along with a portable design, the PSL-40-1T series offers user-friendly front panel control knobs for flexible adjustment of wavelength, pulse width and output power. The wavelength can be tuned throughout the C-band. The pulse width can be tuned from 0.8 to 5 ps, with transform-limited spectral width and a better than -20 dB pedestal. The timing jitter is as low as 50 fs and the side mode suppression is better than -75 dB. An output power of greater than 20 mW obviates the need for an additional optical amplification stage. Options for other wavelength are also available.