All-optical compact encoder assembled by polymer fibres

An all-optical encoder based on a 3x3 crossed structure was assembled by stacking three polymer fibres. The encoding functions were predicated theoretically and demonstrated experimentally with very good agreement. The total insertion loss of the device is about 1dB and the extinction ratio is larger than 10dB. The output state can be controlled by launching optical signals to different input port, and the input state can be identified according to the output state. We believe that the all-optical compact encoder would be used in high-density PICs.