In this article, an all-optical adder based incrementer/decrementer circuit is proposed and described with the help of Semiconductor Optical Amplifier (SOA)-assisted Sagnac switch. The proposed design is more efficient in terms of speed and hardware complexity. The article describes the incrementer/decrementers using a set of optical half adder and full adder. The principle and possibilities of all-optical incrementer/decrementers is explained. A theoretical model is presented and verified through numerical simulation. The new method promises both higher processing speed and accuracy. The model can be extended for studying more complex all-optical circuit of enhanced functionality in which incrementer/decrementers is the basic building block. © Taylor & Francis Group, LLC.