Optically Powered Fiber Optic Sensors

Optically Powered Fiber Optic Sensors (OPFOS) combine the advantages of fiber optic and microelectronic technologies [1-12]. Fiber optic and partially Fiber Optic Sensors (FOS) offer advantages that are significant in the field of variety of industrial, military and medical applications. FOS are immune to electromagnetic interference (EMI), they have low thermal and mechanical inertia, and they are often more sensitive that other sensors [8,9,11,12]. FOS are advantageous in electrically noisy, corrosive, explosive, high-voltage, highcurrent, or high-temperature environments. In addition the use of fiber optic telemetry systems exhibit some advantages of fiber optic communication systems, providing telemetry over long distances and the possibility of control, interrogate or multiplexing many sensors or sensors for different measured into a single system [1,2,3,13]. Microelectronics and partially microelectronic sensors have many advantages too [1,2,3]. The most important advantages are the simplicity of implementation (well understood techniques), simple construction, easy and low powering, low cost, high accuracy (with possible embedded data processing, intelligence), the possibility of miniaturization and integration. The output signal is easy to evaluate (frequency, digital outputs). The output information can be simply evaluated by microcomputer or signal processor. On the other hand the main disadvantage of pure microelectronic sensory systems is caused by electrical transmission of information and powering, i.e. they are not tolerant to EMI and the transmission rate is very low, too. They also cannot be used in explosive, corrosive, high-voltage or high-current environment. That is the reason why such a systems cannot be used for sensing in gasoline, mining or electrical power industry. OPFOS can solve these disadvantages [1-12], by hybridization of fiber optic and microelectronic technologies. The basic principle of this sensory systems is using optical fibers for transmission of control and measurement information, as well as for optically powering of remote microelectronic sensory system [3,5,8,9,10,12]. OPFOS join the advantages of fiber optics and microelectronics sensors (i.e. high sensitivity, flexibility and low cost of electronic sensors with galvanic insulation between two ends (sensory and control), lack of EMI, no need of batteries or main socket for powering, saving the weight, etc.). These properties make it possible to use OPFOS in applications such as measurement of high-voltage, high-current, temperature, pressure, humidity, gas monitoring, etc. in various industrial, medical and military applications in high-voltage, hazardous, explosive, noisy, etc. environment [1-45]. In this paper a review of OPFOS is presented. First the basic properties and the key elements of OPFOS are taking into account. Then OPFOS generalized architectures are discussed. Next the various industrial applications are presented. The paper is closed with short outlook on future trends.