Charge transients induced by optical pulses in CdTe detectors are used to investigate carrier dynamics and collection properties. Various features have been observed in the signals induced by optical excitation in the wavelength range 500nm - 1650nm, depending on the absorption, and the transport mechanism involved. A systematic comparison between charge transients recorded for irradiations through cathode and anode contacts, allows to point out the role of defects near the surface, instability effects, deep level transitions into the bulk, and finally internal photoelectric effects at the contacts.