Enhancing the efficiency of wavelength-shift fiber-based detectors for optical wireless communications

A wavelength-shift fiber-based optical detector promises to revolutionize the deployment of optical wireless communication (OWC) due to its inherent advantages over traditional receivers. These advantages include a flexible structure, a wide field of view (FOV), and a large active area. Despite progress in previous studies, there remains a gap in optimizing the re-utilization of unabsorbed light within wavelength-shift fiber (WSF) and maximizing the efficiency of light focusing onto photodetectors. To address these challenges, this study explores three novel, to the best of our knowledge, approaches to enhance the light conversion and detection efficiency of WSF-based optical detectors. First, a reflective mirror is employed behind the WSF array to increase the light absorption and re-emission probability. Second, a reflective mirror is placed at one end of the WSF array to direct the light toward the opposite end. Third, a tightly bundled WSF array configuration focuses the emitted light onto the photodetector’s active area. Experimental results demonstrate that each approach significantly improves the peak-to-peak voltage. This work presents an optical detector design featuring a large active area of 0.4cm×20cm, based on a blue-to-green color-converting WSF and achieving a high 3-dB bandwidth of up to 48 MHz. This design enables real-time data transmission at rates of 275 Mbps using non-return-to-zero on-off keying (NRZ-OOK) modulation over a distance of 1 m. Additionally, the transmission link operates at over 250 Mbps, with bit error rates (BERs) below the forward error correction (FEC) limit, under a wide FOV of 60°. This work opens exciting possibilities for revolutionizing photodetection schemes in non-line-of-sight free-space optical communications.