Apparatus for signal modulation in a point-to-multipoint optical network, said apparatus being configured to modulate a single-wavelength carrier wave before distribution towards optical receivers installed at endpoints, said apparatus comprising: - a first module configured to modulate said carrier wave according to a first modulation scheme, o by varying the intensity of said carrier wave, thereby representing data intended for an endpoint with a first type of receiver, and o by controlling the phase and/or polarization of said carrier wave during selected periods; - a second module configured to modulate said carrier wave according to a second modulation scheme, o by varying the phase and/or polarization of said carrier wave, thereby representing data intended for an endpoint with a second type of receiver, and o by varying the intensity of said carrier wave during selected periods, wherein said apparatus is configured to select either said first or said second module for modulating said carrier wave during a timeslot, based on type information, said type information indicating which type of optical receivers (101, 102) are installed at said endpoints, said type being said first type for a receiver adapted for intensity detection, or said second type for a receiver adapted for optical field detection. - a first module configured to modulate said carrier wave according to a first modulation scheme, o by varying the intensity of said carrier wave, thereby representing data intended for an endpoint with a first type of receiver, and o by controlling the phase and/or polarization of said carrier wave during selected periods; o by varying the intensity of said carrier wave, thereby representing data intended for an endpoint with a first type of receiver, and o by controlling the phase and/or polarization of said carrier wave during selected periods; - a second module configured to modulate said carrier wave according to a second modulation scheme, o by varying the phase and/or polarization of said carrier wave, thereby representing data intended for an endpoint with a second type of receiver, and o by varying the intensity of said carrier wave during selected periods, wherein said apparatus is configured to select either said first or said second module for modulating said carrier wave during a timeslot, based on type information, said type information indicating which type of optical receivers (101, 102) are installed at said endpoints, said type being said first type for a receiver adapted for intensity detection, or said second type for a receiver adapted for optical field detection. o by varying the phase and/or polarization of said carrier wave, thereby representing data intended for an endpoint with a second type of receiver, and o by varying the intensity of said carrier wave during selected periods, wherein said apparatus is configured to select either said first or said second module for modulating said carrier wave during a timeslot, based on type information, said type information indicating which type of optical receivers (101, 102) are installed at said endpoints, said type being said first type for a receiver adapted for intensity detection, or said second type for a receiver adapted for optical field detection.