HTF Dispersion Compensation Module is used to compensate the accumulated dispersion in the single-mode fiber, and the dispersion coefficient is used to characterize the dispersion value. Regular SMF is around +16~17 ps/(nm*km) at 1550nm. 

To properly manage this, the DCM is built using a special type of dispersion compensating fiber inside the module that has a negative dispersion coefficient ranging from -30 to -300 ps/(nm*km).