Pulse compression is a method of temporarily shortening optical light pulses in order to reduce their pulse duration, as these are broadened by dispersion during optical transmission. It involves ultrashort pulses in the range of picoseconds (`10^-12`) and femtoseconds (`10^-15`).
Linear pulse compression can be applied to pulses that oscillate in and out (chirp). This chirping is shown by the time dependence of the instantaneous frequencies of the optical pulses, which can have rising and falling frequencies. Pulse compression can be used to reduce or completely remove the chirp. This can be done by dispersion compensation; by a pair of prisms, by Bragg gratings, special dispersion compensated optical fibers like the DSF fiber, DCF fiber or the NZDSF fiber. In linear pulse compression, the narrowest pulse width is determined by the optical bandwidth.
In nonlinear pulse compression, on the other hand, the optical bandwidth is first increased using nonlinear interactions such as phase modulation. In most cases, this results in a broadened chirp pulse, which is then compressed in time using linear pulse compression.