An investigation of the use of a fibre optic sensor configured as a stress sensing device is presented. A highly birefringent fiber (Hi-Bi) incorporating a laser diode as a light source is employed and demonstrated for the measurement of the relationship between the coupled light power and applied force or stress. The force-induced coupling of power between the two eigenmodes of the light propagating in the fibre allows the magnitude of the applied force to be measured and controlled. Results obtained have shown that this device may have potential in industrial or robotic sensor applications. Theoretical aspects of the sensor system in this arrangement are discussed.