All-fibre-optic logic 'AND' gate

Operation of an all-fibre-optic-logic AND gate is demonstrated. The logic gate consists of a birefringent fibre, a coiled fibre used as a quarter-wave plate, and a highly birefringent fibre as a polariser. The 9 dB extinction ratio of ‘on’ and ‘off’ states is achieved for the all-fibre-type AND gate.