A method of producing a-switched thulium doped fibre lasers, TDFLs, by preparing multiwalled carbon nanotubes, MWCNTs, is provided characterized in that, the method includes the steps of mixing MWCNTs homogenous solution into dilute polyvinyl alcohol, PVA polymer solution, drying at room temperature to produce film, sandwiching film between 2 FC/PC fibre connectors, integrating into laser cavity and configuring pulse repetition rate of TDFL wherein the method produces a stable pulse train.