Fiber optic monitoring system ready for 4-20mA industrial control standard

The proposed work has the aim to design a full analog electrical circuitry to convert the wavelength-encoded signal coming from a generic Optical Fiber Sensor (OFS) into a monotonic electrical current. The electrical circuitry, related to the single OFS, is composed by one or more Sensing Circuit in function of the dynamic range or if a compensate measurement is needed. The mentioned circuit has the key strength to be robust and reliable: it avoids any kind of digital processing unit; it is completely protected from internal leakage currents due to an optical isolator which has also the aim to reduce noise; then the electrical module has also the capability to restore the output if a source fluctuation occurs or if a loss increment happens; if a loop interruption occurs for a connection or a device breaks down, the output current automatically raise to a threshold value. The proposed concept has been validated with experimental measurement, sensing a temperature deviation of more than 20°C with two different Fiber Bragg Grating (FBG) sensors, as a possible scenario in which it can be employed.