The fiber-optic sensor head (2) for an optical current or magnetic-field sensor (1) has an optical fiber which , includes a magnetooptically active sensor fiber (3) which is optically connected to at least one polarization-defining element (4; 5) , wherein the sensor fiber (3) can be arranged in a magnetic field to be measured or around a conductor (L) carrying the current to be measured and is in the form of a coil (8), with the coil (8) defining a coil plane (A) with a surface normal (Ns) , and with the at least one polarization-defining element (4; 5) having a marked axis (f) . The sensor head (2) is flexible in the area of the sensor fiber (3), and an adjustment means (10) is provided for adjustment of a predeterminable angle (5 between the marked axis (f) and the surface normal (Ns) or for adjustment of predeterminable angles β, β' between the marked axes (f) and the surface normal (Ns) . It has been found that the angle or the angles β, β! influence the calibration of the sensor. The adjustment means (10) advantageously contains a mount body (11) to which the at least one polarization-defining element (4; 5) is fixed. The angle or the angles β, β' is or are predetermined by the mount body (11) - The markings (9a, 9b) make it possible to ensure that the coil (8) has an integer number of turns. (figure 1)