A system for detecting signal components of light induced by multiple excitation sources, comprising: a flow channel configured for the flow of particles, the flow channel comprising optical interrogation zones; a non-modulating first excitation source configured to direct a first light beam of a first wavelength at a non-modulated intensity onto a first optical interrogation zone; an intensity modulating second excitation source configured to direct a second light beam of a second wavelength with an intensity modulated over time at a modulation frequency onto a second optical interrogation zone, wherein the second wavelength is different from the first wavelength; a detector subsystem comprising a set of detectors configured to detect light emitted from fluorescence-molecule containing particles flowing through the optical interrogation zones and to convert the detected light into an electrical signal; and a processor configured to receive the electrical signal from the detector subsystem, to de-modulate electrical signal that is modulated, and to determine signal components from the light detected from each of the optical interrogation zones, characterized in that the flow channel comprises a third optical interrogation zone and the optical interrogation zones are spatially separated along the flow channel, the system comprises an intensity modulating third excitation source configured to direct a third light beam of a third wavelength with an intensity modulated over time at the same modulation frequency as the second light beam onto the third optical interrogation zone, wherein the wavelength of the third light beam is different from the wavelength of the first and the second light beam and the second and the third optical interrogation zones are on different sides of the first optical interrogation zone to which the non-modulated first light beam is directed, and the electrical signal is a total electrical signal from the detected light from each of the optical interrogation zones. a flow channel configured for the flow of particles, the flow channel comprising optical interrogation zones; a non-modulating first excitation source configured to direct a first light beam of a first wavelength at a non-modulated intensity onto a first optical interrogation zone; an intensity modulating second excitation source configured to direct a second light beam of a second wavelength with an intensity modulated over time at a modulation frequency onto a second optical interrogation zone, wherein the second wavelength is different from the first wavelength; a detector subsystem comprising a set of detectors configured to detect light emitted from fluorescence-molecule containing particles flowing through the optical interrogation zones and to convert the detected light into an electrical signal; and a processor configured to receive the electrical signal from the detector subsystem, to de-modulate electrical signal that is modulated, and to determine signal components from the light detected from each of the optical interrogation zones, characterized in that the flow channel comprises a third optical interrogation zone and the optical interrogation zones are spatially separated along the flow channel, the system comprises an intensity modulating third excitation source configured to direct a third light beam of a third wavelength with an intensity modulated over time at the same modulation frequency as the second light beam onto the third optical interrogation zone, wherein the wavelength of the third light beam is different from the wavelength of the first and the second light beam and the second and the third optical interrogation zones are on different sides of the first optical interrogation zone to which the non-modulated first light beam is directed, and the electrical signal is a total electrical signal from the detected light from each of the optical interrogation zones.