We propose a novel technique to regenerate the optical signal in a relay-based free space optical link. Our proposed regenerator is based on an Electro-absorption modulator whose optical input is the signal to be regenerated, while the electrical input is extracted by processing a part of the optical input signal. The signal at the output of the proposed regenerator based relay has lower intensity fluctuations compared to a conventional optical amplifier based relay. We have tested our proposed regenerator-based relay under medium and strong turbulence conditions by choosing the refractive index structure parameters as 5×10-15 m-2=3 and 5×10-10 m-2=3, respectively. Our simulation results show that the proposed regenerator-based relay reduces the received power penalty by 3.5 dB compared to the conventional amplifier-based relay, under strong turbulence conditions.

Ultrawideband (UWB) signals have low allowable transmission powers. To enhance the coverage and capacity of UWB signals, a cost-efficient solution for the access network has been proposed and simulated. The access network is based on gamma–gamma free-space optical channel model, which is employed between the central unit and the four different carrier-free radio access units (RAUs). All-optical generation and transmission of UWB signals at a rate of 1.5 Gbps to each RAU are demonstrated. Bit error rate results are obtained to observe the performance of the UWB signals received at the mobile stations. The proposed architecture requires minimum deployment cost and gives acceptable bit error rate results.

Recent advancements in power electronic switches provide effective control and operational stability of power grid systems. Junction temperature is a crucial parameter of power-switching semiconductor devices, which needs monitoring to facilitate reliable operation and thermal control of power electronics circuits and ensure reliable performance. Over the years, various junction temperature measurement techniques have been developed, engaging both non-optical and optical-based methods, highlighting their advancements and challenges. This review focuses on several optical sensing-based junction temperature measuring techniques used for power-switching devices such as metal-oxide-semiconductor field-effect transistors (MOSFETs) and insulated-gate bipolar transistors (IGBTs). A comprehensive summary of recent developments in infrared camera (IRC), thermal sensitive optical parameter (TSOP), and fiber Bragg grating (FBG) temperature sensing techniques is provided, shedding light on their merits and challenges while providing a few possible future solutions. In addition, calibration methods and remedies for obtaining accurate measurements are discussed, thus providing better insight and directions for future research.