A fiber-optic current sensor comprising a light source generating light with a coherence length Lc, a first beam splitter splitting the light from said light source into a first and a second branch (21a, 21b), a second beam splitter combining the light from said first and second branches (21a, 21b), a polarization-maintaining connecting fiber adapted to carry light in first and second, mutually orthogonal polarization modes and receiving light from said second beam splitter for a first passage through said connecting fiber, a sensor head, wherein said sensor head is adapted and structured to receive light waves from said first and said second polarization mode of said connecting fiber, to generate a current-dependent phase shift between said light waves, and to reflect said light waves back into said connecting fiber with switched polarizations for a second passage through said connecting fiber, a detector located to detect a light intensity resulting from the interference of said waves after their second passage through said connecting fiber, characterized in that the fiber-optic current sensor further comprises: a first releasable connector in said first branch, and a second releasable connector in said second branch, wherein said first branch is adapted to carry light in a first and a second polarization mode between said first connector and a select one of said first or said second beam splitters (20, 22), and wherein said second branch is adapted to carry light in a first and a second polarization mode between said second connector and said select beam splitter, wherein without angular misalignment of said connectors (6a, 6b), light traveling towards the sensor head is in the first polarization modes of the first and second branches (21a, 21b), and wherein abs L 11 + L 21 − L 12 − L 22 > Lc with L11 being an optical path length of the first polarization mode in the first branch between the first connector and the select beam splitter, L12 being an optical path length of the second polarization mode in the first branch between the first connector and the select beam splitter, L21 being an optical path length of the first polarization mode in the second branch between the second connector and the select beam splitter, and L22 being an optical path length of the second polarization mode in the second branch between the second connector and the select beam splitter. a first releasable connector in said first branch, and a second releasable connector in said second branch, wherein said first branch is adapted to carry light in a first and a second polarization mode between said first connector and a select one of said first or said second beam splitters (20, 22), and wherein said second branch is adapted to carry light in a first and a second polarization mode between said second connector and said select beam splitter, wherein without angular misalignment of said connectors (6a, 6b), light traveling towards the sensor head is in the first polarization modes of the first and second branches (21a, 21b), and wherein abs L 11 + L 21 − L 12 − L 22 > Lc with L11 being an optical path length of the first polarization mode in the first branch between the first connector and the select beam splitter, L12 being an optical path length of the second polarization mode in the first branch between the first connector and the select beam splitter, L21 being an optical path length of the first polarization mode in the second branch between the second connector and the select beam splitter, and L22 being an optical path length of the second polarization mode in the second branch between the second connector and the select beam splitter. L11 being an optical path length of the first polarization mode in the first branch between the first connector and the select beam splitter, L12 being an optical path length of the second polarization mode in the first branch between the first connector and the select beam splitter, L21 being an optical path length of the first polarization mode in the second branch between the second connector and the select beam splitter, and L22 being an optical path length of the second polarization mode in the second branch between the second connector and the select beam splitter.