We propose a reconfigurable 8PSK/8QAM modulator implementation by employing two cascaded QPSK modulators with an interferometer in between. With simple control of bias voltage of the interferometer, a flexible switching between 8PSK/8QAM can be achieved. The transmission performance of the generated 8PSK/8QAM signals over different link scenarios is compared via numerical simulations. The results reveal that the proposed implementation has the capability of maximizing transmission distance in the case of ynamic optical network.