An optoelectronic device. The optoelectronic device operable to provide a PAM-N modulated output, the device comprising: M optical modulators, M being an integer greater than 1, the M optical modulators being arranged in a cascade, the device being configured to operate in N distinct transmittance states, as a PAM-N modulator, wherein, in each transmittance state of the N distinct transmittance states, each of the M optical modulators has applied to it a respective control voltage equal to one of: a first voltage or a second voltage.