This book is about the material which we can use for Advance Process Control and Instrumentation. Sensors, Lasers are essential components in any device that uses a digital signal processor. Digital systems, however complex and intelligent they might be, must receive information from the outside world. Sensors are the interface devices between various physical values and electronic circuits that “understand” only a language of moving electrical charges. Many of them are well known, but describing them is still useful for students and those who look for a convenient reference. It is the author’s intention to present a comprehensive and up-to-date account of the theory (physical principles), design, and practical implementations of various fiber, sensors applications. In most cases, the authors have tried to strike a balance between a detailed description and simplicity of coverage. It is clear that one book cannot embrace the whole variety of fiber, sensors and PID controllers and their Applications.