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Matata, Tinopera (2024) Plastic optical fibre couplers with wavelength division multiplexing capability for short-range peer-to-peer communication in networking and industrial applications. Doctoral thesis, London Metropolitan University.
This thesis presents a study on the design and simulation of adjustable, multi-output plastic optical fibre (POF) array couplers for wavelength-division multiplexed (WDM) transmission in the visible spectrum. The research focuses on three configurations—1×2, 1×4, and 1×8—and introduces a novel architecture that allows precise control of optical power spliting ratios, offering greater flexibility than conventional couplers with fixed branching ratios.
The innovation lies in two integrated design mechanisms that enable both coarse and fine adjustment of optical power distribution. The first is the coupling POF immersion-depth adjustment, which provides coarse tuning by varying the insertion depth of the coupling fibre into the backbone fibre to control the power received at each output port. The second is the reflector-length adjustment, which allows fine control by modifying the reflector length between the polished surfaces of the backbone and coupling fibres. Together, these mechanisms permit accurate tailoring of the optical power split at the design stage, eliminating the need for post-fabrication calibration and enhancing design flexibility.
This controllability improves optical network performance by enabling power optimisation across all ports, thereby reducing the need for repeaters, simplifying system design, and lowering overall cost. The proposed designs were evaluated using theoretical ray-optics modelling and LightTools ray-tracing simulations, which confirmed that the couplers exhibit high coupling efficiency and low insertion loss.
Simulation results show that the 1×2 coupler delivers an average of 46.5% of the input power to each output port (93% efficiency, 3.3 dB insertion loss per port). The 1×4 coupler provides approximately 22% per port (86% efficiency, 6.7 dB insertion loss), while the 1×8 coupler distributes 8% per port (62% efficiency, 11 dB insertion loss). All designs comply with the GR-1209-CORE specification for insertion loss per port. Although primarily optimised for signal reception, modifications were simulated to evaluate their suitability as transmitting couplers, indicating promising potential for future development.
This work advances the field of short-reach optical communications by proposing design-time adjustable POF array coupler architecture that combines mechanical simplicity, presettable power ratios, and high optical efficiency. The study demonstrates a cost-effective, scalable path toward reliable connectivity for industrial and in-home networks, based entirely on simulations.
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