Simple and reconfigurable photonics-based half adder and half subtracter

A photonics-based digital signal processing structure that has the ability of realising half addition and half subtraction, is presented. It is based on applying the two digital inputs into a dual-polarisation modulator and designing the modulator bias voltages to realise the logical operations. After photodetection, a Sum output and a Carry output for half addition, or a Difference output and a Borrow output for half subtraction, can be generated. Switching between the half addition operation and the half subtraction operation can be achieved by simply changing a digital input amplitude and a modulator bias voltage. The proposed photonics-based digital signal processing structure is theoretically analysed. Using the system parameter setting obtained from the theoretical analysis, half addition and half subtraction operations are experimentally demonstrated.