The Picosecond Laser Source module (PSLS) consists of a monolithically integrated mode-locked laser mounted on a submount for temperature stabilisation and packaged in a compact, surface-mountable module with a single-mode fibre pigtail and V® connector. It is based on a multi-section SIPBH (Semi-Insulating Planar Buried Heterostructure) MQW mode-locked laser on GaInAsP / InP and was fabricated in an in-line extended cavity configuration. The device integrates a gain and absorber section, as well as a DBR grating for on-chip fine tuning of the centre wavelength by carrier injection. The device offers two different modes of operation; passive and hybrid mode-locking. Under hybrid mode-locking, the pulse repetition rate is locked to an electrical clock signal with a required RF power of only 10-15 dBmel resulting in an extremely stable and robust operation with low amplitude noise as well as high pulse-to-pulse phase stability. The monolithically integrated mode-locked laser module was developed in cooperation with the Fraunhofer Institut für Nachrichtentechnik, Heinrich-Hertz-Institut in Berlin, and the cooperation with the mode-locked laser research team is gratefully acknowledged.