The invention relates to a folded Mach-Zehnder modulator. The modulator may comprise a beam splitter configured to split an input light beam into a plurality of light beams. The modulator may comprise a plurality of Mach-Zehnder devices configured to receive one or more of the plurality of light beams. The modulator may comprise a U-turn section configured to receive light beams from the Mach-Zehnder devices and to change the direction of the light beams by substantially 180 degrees. The modulator may comprise a polarisation management section configured to combine light beams received from the U-turn section and to output a polarisation multiplexed phase modulated light beam.
