TOPTICA’s difference frequency comb DFC operates with CERO technology (“zero-vCEO”) which obtains a phase-stable laser output with an inherently vanishing frequency offset. To achieve this, femtosecond laser pulses centered at 1560 nm are generated with a mode-locked Er3+ -doped fiber-oscillator. Subsequent amplification and coherent spectral broadening of the pulses in a nonlinear fiber creates a broad supercontinuum. Difference frequency generation (DFG) between the lower and upper spectral parts of the supercontinuum produces a frequency comb output centered at 1560 nm. Since the two spectral parts have identical carrier-envelope-frequencies, the resulting comb is offset-free due to common-mode suppression in the DFG process. In other words, the carrier-envelope frequency is fixed at zero automatically and no active stabilization of the phase is necessary. This passive approach results in improved phase-stability and higher reliability compared to conventional active stabilization techniques. The absence of an electronic feedback-loop for phase stabilization leads to a reduced complexity of the system and circumvents electronic noise limitations. The system comes with an integrated radio frequency reference and locking electronics to synchronize the repetition rate, or it can be locked to an optical reference. The main unit DFC-CORE provides four νCEO-stabilized outputs at 1560 nm. Various extensions are available to convert the outputs to any desired wavelength from 420 – 2200 nm. Thus, all cw-lasers in this wavelength range can be locked to the frequency comb, in particular TOPTICA’s research-grade diode lasers are designed to operate with the DFC.