A passive fiber-optic depolarizer

A passive fiber-optic depolarizer for avoiding noise due to input polarization fluctuations in polarization-sensitive optical sensors is described. It consists of a 2*2 polarization-maintaining coupler (with a coupling ratio of >2/3) having two fiber leads spliced together with their respective fast axes crossed, forming a recursive loop structure. Essentially complete depolarization was experimentally demonstrated. This approach requires no active elements and is applicable even to extremely narrow bandwidth laser sources.<
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