Research Of Metal Coating On Fiber Bragg Grating And The Sensing Charateristics After Metallization

In view of the advantages over conventional sensors, fiber Bragg grating（FBG） andoptical fiber intelligent metal structures（OFIMS） which based on an embedded FBGhave the potential to be widely employed as sensing techniques in even all kinds ofdefense and civil fields, such as spacecraft, shipbuilding industry, bridge engineering,and so on. The key component of OFIMS is the compound structure of FBG and metalcomponent. With the traditional methods, OFIMS was integrated by bonding the FBGand metal organ with an epoxy adhesive technology. However, this will bring variousdisadvantages, such as unstable, easily distorted, easily spoiled by high temperature orhumidity, which make people distracting their attention on a new integrated processwhich was called adhesive-free bond technology.The most important of adhesive-free bond technology is metal coating the FBG.However, with the existing process such as sputtering, CVD, sol-gel method,electroplating, and so on, either special equipment or complex process control isrequired. Even the structure of FBG could be destroyed in these kinds of technology.Therefore it is important and meaningful to make the metallization of FBG controllable,low-cost and applicable in large-scale.In this dissertation, a simple and convenient technique for FBG metalizing and anadhesive-free bond technology for OFIMS integrating were reported, which was basedon the electroless plating and metal wedding, respectivly. Metal coated FBG andFBG-metal compound organ were fabricated successfully. OM, SEM, EDS, XPS, XRD,thermal variations, temperature and strain sensing experiment were used for the coatingand FBG charactering, and the main results are as follow:1. A method to metalize the optical fiber and FBG without fiber coarsensing ispresented, the results of SEM, XPS and XRD indicate that the alloy clad was verysmooth, flat and compact, and in amorphous state with a composition of Ni71.73at%and P28.27at%.2. With the results of orthogonal experiment, it was confirmed that:①Theparameters which can get the best bonding force between the coating clad and FBG are:NiSO₄·6H₂O28g/L, NaH₂PO₂·H₂O24g/L, H₃BO₃10g/L, C₃H₆O₂20mL/L, pH3.0,temperature80℃,40min.②The parameters which can get the fastest deposition rateare: NiSO₄·6H₂O23g/L, NaH₂PO₂·H₂O29g/L, H₃BO₃20g/L, C₃H₆O₂15mL/L, pH 3.5, temperature80℃,40min.③The parameters which can combine the best bondingforce and the fastest coating deposition rate are: NiSO₄·6H₂O21g/L, NaH₂PO2·H₂O23g/L, H_BO₃20g/L, C₃H₂0mL/L, pH3.5, temperature85℃,40min.3. The influence of coarsening on the bonding force and sensing performance ofFBG was analysied, the effect of metallization was also studied, respectively. Theresults show that: fiber coarsening would weaken the intensity of center Braggwavelength with a larger extent, also make the temperature sensing accuracy droppedsignificantly. However, there was nearly no negative impact which caused bymetallization, in addition, the negative impact which brought by the fiber coarseningcan repair with metal coating on the surface of FBG.4. FBG-metal compound structure was integrated with adhesive-free bondtechnology which based on metal bedding, successfully. The strain sensingcharacterization indicated that: the precision, stability, and linearity and reproducibilityof FBG are retented by adhesive-free bond technology, while the FBG-metal compositestructure which integrated by the adhesive method shows a poor performance on thestrain loading experiment. It was considered that FBG can not be completely fixed onthe metal organ by adhesive method, then, when the strain was added to a sufficientlyheavy, a relative displacement between FBG and the metal component was occurred,thus affecting the accuracy of measuremental results.