An apparatus including a receiver and an extractor is provided for determining a physiological parameter of a living being. The receiver is adapted to receive iterating optical signals, the optical signal including sequences, and a sequence including at least two bright periods during which a transmit light source adopts an on state and at least one dark period during which no transmit light source adopts an on state, and the at least two bright periods being irregularly arranged within a sequence. In addition, the apparatus includes an extractor. The extractor extracts information on the physiological parameter from a receive signal, the extractor being adapted to extract, on the basis of the information on the arrangement of the bright periods within the sequence, a value of a magnitude indicating a vital parameter.
