An assembly line in-situ calibration arrangement, optical sensor arrangement and a method for calibration of an optical sensor arrangement are presented. A calibration arrangement comprises a calibration head comprising at least one calibrated light source located behind an aperture in a housing and being electrically connected to a power terminal. A power source is connected to the power terminal, the power source comprising a switching unit electrically connected to the at least one light source. An interface unit is connected to the switching unit by means of an interface connection, wherein the interface unit is arranged to control the switching unit. A control unit is connected to the interface unit, wherein the control unit is arranged to drive the interface unit such that the at least one light source is switched to emit a calibration pulse sequence to be received by the optical sensor arrangement to be placed with respect of the aperture. The calibration pulse sequence is arranged to initiate a calibration mode of operation of the optical sensor arrangement.