Phase modulation occurs when an external physical parameter—such as strain, temperature, pressure, or acoustic waves —interacts with the optical fiber. This interaction alters the effective optical path length that the light travels. Optical phase-modulation technique is a very powerful tool used in a wide variety of high performance photonic systems. Fiber-optic sensors and gyroscopes, integrated-optics sensors, or high-performance photonic integrated circuits are some examples of photonic systems where the optical. In the field of interferometric fiber-optic sensing, the phase-shifting technique is well known as a highly efficient method for retrieving the phase signal from the interference light intensity. Crucially, even changes on the scale of nanometers—a fraction of.
