This paper describes the compact design of a torque sensor using optical technique and its fabrication for wearable and quadruped robots. The torque generated can only be measured by placing torque sensor on each joint, which makes the joint bulky and heavy, adding extra load to be carried by robot. In this paper we proposed a compact and light weight design for the torque sensor. This sensor can measure torque of robots links by detecting torsion. The optical technique is used to detect angular displacement in the joints. The torque can be calculated by using torque and twist-angle relation. The proposed design is simulated by FEM software (ANSYS) and it shows successful measurements of the torque with a load capacity of 50 Nm, which is sufficient for the torque generated in wearable and quadruped robots joints. The designed optical torque sensor is manufactured by EDM (Electrical Discharge Machining). The optical torque sensor was calibrated and several experiments were conducted to ratify its feasibility with the wearable and quadruped robots.