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Optical fiber microducts are joined together by mechanical joints. These mechanical joints are bulky, require more space per joint, and are prone to air pressure leakage and water seepage during service. A battery powered electrofusion welding system with a resistive-type joint has been recently developed to replace mechanical joints. These resistive-type electrofusion joints require physical connectors for power input. Due to a different installation environment, the power input connectors of resistive optical fiber microduct joints may corrode over time. This corrosion of connectors will eventually cause water seepage or air pressure leakage in the long run. Moreover, due to connector corrosion, resistive-type optical fiber microduct joints cannot be re-heated in future if the need arises. In this study, an inductively coupled electrofusion-type joint was proposed and investigated. This inductive-type electrofusion joint is not prone to long-term corrosion risk, due to the absence of power connectors. Inductive-type electrofusion joints can be re-heated again for resealing or removal in the long run, as no metal part is exposed to the environment. The battery powered inductive welding system can be easily powered with a 38 volts 160 watt-hour battery. The inductive-type electrofusion joint was welded within one second, and passed a 300-newton pull strength test and a 10-bar air pressure leakage test. It was demonstrated that the power input requirement for inductive electrofusion joints is 64% higher than that of resistive electrofusion joints. However, these inductive joints are relatively easy to manufacture, inexpensive, have no air leakage, and no water seepage risk in highly corrosive environments. Full article

At present, optical fiber microducts are joined together by mechanical type joints. Mechanical joints are bulky, require more space in multiple duct installations, and have poor water sealing capability. Optical fiber microducts are made of high-density polyethylene which is considered best for welding by remelting. Mechanical joints can be replaced with welded joints if the outer surface layer of the optical fiber microduct is remelted within one second and without thermal damage to the inner surface of the optical fiber duct. To fulfill these requirements, an electro-thermal model of Joule heat generation using a copper coil and heat propagation inside different layers of optical fiber microducts was developed and validated. The electro-thermal model is based on electro-thermal analogy that uses the electrical equivalent to thermal parameters. Depending upon the geometric shape and material properties of the high-density polyethylene, low-density polyethylene, and copper coil, the thermal resistance and thermal capacitance values were calculated and connected to the Cauer RC-ladder configuration. The power input to Joule heating coil and thermal convection resistance to surrounding air were also calculated and modelled. The calculated thermal model was then simulated in LTspice, and real measurements with 50 µm K-type thermocouples were conducted to check the validity of the model. Due to the non-linear transient thermal behavior of polyethylene and variations in the convection resistance values, the calculated thermal model was then optimized for best curve fitting. Optimizations were conducted for convection resistance and the power input model only. The calculated thermal parameters of the polyethylene layers were kept intact to preserve the thermal model to physical structure relationship. Simulation of the optimized electro-thermal model and actual measurements showed to be in good agreement. Full article