The first polarisation-maintaining actively modelocked erbium fibre ring la
ser (ML-EFRL) operating at a base rate of 40GHz is presented. The laser gen
erates highly stable and virtually transform-limited 1.2-1.9ps pulses tunab
le over 40nm with a timing jitter of < 0.1 ps. These represent the shortest
pulses and lowest timing jitter generated by a 40GHz ML-EFRL.