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