Multiplication of Repetition frequency of Erbium doped pulsed fiber Laser

We designed a set-up with external Fabry-Perot cavity including the mode-matching lenses, silver mirrors and locking scheme to multiplicate erbium-doped fiber laser comb. The cavity is coupled to fiber output via fiber collimator in the set-up. Initial repetition rate frequency of 250 MHz was multiplicated to 1 GHz on the Fabry-Perot cavity with 1 GHz free spectral range and a pair of 40 nm silver mirrors in plan-concave configuration