With mode-locked fiber lasers typically constructed from several meters of fiber, operational repetition rates are generally in the range of a few tens of megahertz. For some pump–probe applications, where long decay times may be investigated, the pulse repetition rates may need to be increased so that after excitation, the following pump pulse does not arrive during the investigated decay dynamics. With fiber mode locked fiber lasers, this can be readily achieved simply by adding more passive fiber and mode locked operation with cavities several kilometers long has been demonstrated.91 For operation in the normally dispersive regime, for example, with a Yb-based gain medium, the overall pulse generation process leads to a monotonic and positive frequency sweep (an up-chirp) being generated across the pulses and with dispersion dominating the process, the generated pulses exhibit durations many times the transform-limited duration. This can be advantageous in that the pulse energy, which is unlimited as would not be the case for soliton operation, can be scaled to the microjoule level, while avoiding the problems of nonlinearity because of the extended pulse durations. Consequently, such pulses can also be used as the seed sources for fiber-based chirped pulse amplifier schemes, where external pulse compression schemes such as grating pairs can be used to recompress the pulses to the picosecond regime. Many giant chirp mode-locked fiber oscillators, however, exhibit bandwidths that are less than a nanometer. Consequently, with durations in the nanosecond regime, typical conventional grating pair separations in excess of 50 m may be required for pulse compression, which is quite impractical. In such circumstances, chirped fiber grating technology can be used for pulse compression, but this then limits the operational pulse energies. In a cavity similar to that of Fig. 10, Woodward et al.92 incorporated 840 m of single-mode fiber, generating pulses of 1.02 ns at a fundamental repetition rate of 244 kHz at 1058 nm with a pulse energy of , which exhibited the characteristic square sided spectra associated with giant chirped pulses, with a bandwidth of 0.8 nm. On coupling from the cavity, the pulses traversed a fiber-coupled circulator incorporating a 40-cm long chirped fiber Bragg grating, which compressed the pulses by almost two orders of magnitude to 11 ps. The compressed or uncompressed pulses can be amplified and allow supercontinuum generation with picosecond and nanosecond pumping, respectively, at low (100 s kHz) repetition rate and low average powers, of the order of a few 10 s mW, for application in time-resolved spectroscopy.