Abstract: This study implemented carry-free addition of two vectors in parallel on the ternary optical computer. Its key part is made up of a piece of monochromatic LCD, whose volume is 38.0 X 65.5 X 2. 2mm3 and power is 0. 3mw, and a layer of polaroid on either side. The parallel and carry-free addition was realized in three steps by defining four transformations on Modified Signed-Digit(MSD) number system. And the required time of the addition is independent of the digits of operands. An experiment certified the feasibility and correctness of the parallel and carry-free addition on the ternary optical computer. The system can finish the addition of two numbers with 680 bits in MSD code in three steps and in fully parallel.

Key words: Ternary optical computer, Modified signed-digit, In parallel, Carry-free