A current sensor comprising: a light source, a first linear polarizer receiving light from the light source and generating polarized light, and a sensor head with - a retarder receiving light from the first linear polarizer, - wherein the retarder detuning |Δρ| is in a range of 1° to 30° and serves for reducing a temperature-dependence in the measurement signal, - a sensing fiber arranged to receive light from the retarder, wherein the sensing fiber is adapted to be looped at least once around a conductor carrying a current to be measured, - a mirror arranged to receive light from the sensing fiber, and - a Faraday rotator arranged between the retarder and the mirror, wherein the Faraday rotator rotates the light by (22.5° + M•45°) ± 10°, with M being an integer number ≥ 0, - the current sensor further comprising at least one detector adapted to measure at least one signal of light returning from the sensor head through the first linear polarizer, characterized in that - the retarder has a retardation of 90° + Δρ + N•180° or 180° + Δρ + N•180° with retarder detuning Δρ ≠ 0 and N being an integer number ≥ 0, and that - a retardation of the retarder is such that it compensates at least partially for a temperature dependence of a Verdet constant of the sensing fiber and for a temperature dependence of a rotation angle generated by the Faraday rotator. a light source, a first linear polarizer receiving light from the light source and generating polarized light, and a sensor head with - a retarder receiving light from the first linear polarizer, - wherein the retarder detuning |Δρ| is in a range of 1° to 30° and serves for reducing a temperature-dependence in the measurement signal, - a sensing fiber arranged to receive light from the retarder, wherein the sensing fiber is adapted to be looped at least once around a conductor carrying a current to be measured, - a mirror arranged to receive light from the sensing fiber, and - a Faraday rotator arranged between the retarder and the mirror, wherein the Faraday rotator rotates the light by (22.5° + M•45°) ± 10°, with M being an integer number ≥ 0, - the current sensor further comprising at least one detector adapted to measure at least one signal of light returning from the sensor head through the first linear polarizer, characterized in that - the retarder has a retardation of 90° + Δρ + N•180° or 180° + Δρ + N•180° with retarder detuning Δρ ≠ 0 and N being an integer number ≥ 0, and that - a retardation of the retarder is such that it compensates at least partially for a temperature dependence of a Verdet constant of the sensing fiber and for a temperature dependence of a rotation angle generated by the Faraday rotator. - a retarder receiving light from the first linear polarizer, - wherein the retarder detuning |Δρ| is in a range of 1° to 30° and serves for reducing a temperature-dependence in the measurement signal, - a sensing fiber arranged to receive light from the retarder, wherein the sensing fiber is adapted to be looped at least once around a conductor carrying a current to be measured, - a mirror arranged to receive light from the sensing fiber, and - a Faraday rotator arranged between the retarder and the mirror, wherein the Faraday rotator rotates the light by (22.5° + M•45°) ± 10°, with M being an integer number ≥ 0, - the current sensor further comprising at least one detector adapted to measure at least one signal of light returning from the sensor head through the first linear polarizer, characterized in that - the retarder has a retardation of 90° + Δρ + N•180° or 180° + Δρ + N•180° with retarder detuning Δρ ≠ 0 and N being an integer number ≥ 0, and that - a retardation of the retarder is such that it compensates at least partially for a temperature dependence of a Verdet constant of the sensing fiber and for a temperature dependence of a rotation angle generated by the Faraday rotator.