Illustration of the sensing principle. (a) The light inside the core of the optical fiber is reflected by the iron thin film; (b) The light escape of optical fiber after the iron thin film is depleted.The proposed sensor possesses a number of advantages compared to other corrosion sensors. The till interpretation of the results is easy and direct because of the very simple sensing principle. It can measure any corrosive agents in the surrounding environment, including chloride ion and carbon dioxide. Mass Inhibitors,Modulators,Libraries production of the sensors at low cost is feasible because single mode telecommunication optical fiber can be employed and a large number of optical fibers can be sputtered at a time. Moreover, thanks to the small size of the sensor, it can be retrofitted to existing structures.
Several sensors can be multiplexed with the use of an optical splitter (Figure 2) and the reflectivity at the end Inhibitors,Modulators,Libraries of each sensor can be measured with optical time domain reflectometer (OTDR). The principle of the OTDR is that it sends a short laser pulse to the optical fiber and measures the intensity of the reflected light and the corresponding arrival time. When the pulse reaches the fiber end, light is reflected back. By using the optical splitter, the laser pulse from the OTDR travels to different sensors. If the differential distances between each sensor and the optical splitter are all significantly longer than the spatial resolution of the OTDR, the reflectivity Inhibitors,Modulators,Libraries of all sensors can be obtained from a single OTDR reading.
To eliminate the fluctuation of light source and the insertion losses, a cleaved optical fiber without coating is connected to the optical splitter as a reference. A typical OTDR reading of the multiplexed sensors is shown in Inhibitors,Modulators,Libraries Figure 3. The variations of the light source, insertion losses at the OTDR and the optical splitter can be eliminated by adjusting the whole curve up or down so that the peak for the reference signal reaches the same value in all subsequence OTDR readings. As shown in Figure 3, there are two additional peaks arising from the optical splitter. One is at the connection between the OTDR and the optical splitter, and the other is at the outlet of the optical splitter. Also, the two small peaks located between sensors 1 and 2, 4 and 5 are due to the connection between the extension optical fiber cord and the packaged sensor.Figure 2.
Schematic diagram of using OTDR and optical splitter to measure the reflectivity of several sensors in single OTDR reading.Figure 3.Typical OTDR reading of multiplexed sensors.3.?Field Brefeldin_A Trial of the SensorA field trial was arranged to test the performance of the sensor in aggressive environments. Ten sensors were installed in two piers of a footbridge located at the seafront of the southern part of Hong Kong www.selleckchem.com/products/Axitinib.html Island. Under normal high tide conditions, the piers of the footbridge are partially submerged in seawater. Also, wind carries chloride ions and moisture to the surface facing the sea.