Abstract In this work, a novel and compact mode selective coupler based on an asymmetric dual core photonic crystal fiber with a thermo-responsive core is proposed and numerically studied. Simulation results show that high conversion efficiencies are achieved between LP 01 and LP 11 modes in the O-band with a wide bandwidth of 24.55 nm and a mode conversion efficiency over 60% when it has a total length of 3.15 mm and the operating wavelength is 1310 nm. In addition, the thermally tuneability was evaluated when this device was submitted to thermal changes from 15°C to 35°C. The results evidence that thermal effect allows to control the operating wavelength and the mode coupling efficiency of the mode converter when it is used to couple energy from the LP 01 mode to the LP 11 mode. Therefore, the proposed device could be useful in high-bandwidth mode division multiplexed communication systems.