The invention relates to an apparatus for dynamically controlling the gain of an optically pumped optical amplifier, and the optical amplifier including such apparatus, which utilizes a multiplying digital to analog converter to implement a digitally adjustable analog feed forward control of a source of pump radiation of the optical amplifier. 5 and 30 nm and that has microporous and crystallized walls with a thickness of between 1 and 60 nm, whereby said elementary spherical particles have a maximum diameter of 200 microns. Malfunctions of the electric motors are detected during the operation.