Unidirectional integrated optical elements for secure communication systems in multimode optical fibers

In bidirectional transmission, existing optical communication systems suffer from propagation loss, crosstalk, delay in transmission, back-reflection, signal leakage, noise accumulation, and physical-layer security vulnerability. To address these limitations, this paper proposes a secure unidirectional optical communication system over multimode optical fiber. A proposed system includes optical isolators, one-way transmission, and mode-selective filtering to minimize intermodal interference. Unidirectional transmission: suppresses crosstalk and enhances signal integrity by controlling the propagation of the signal based on the dominant transmission mode. The system was tested using simulations with realistic channel conditions, such as attenuation, dispersion, and noise. The performance was evaluated in terms of signal to noise ratio (SNR), bit error rate (BER), and suppression of crosstalk. The proposed model gave a BER of 2 × 10 −4 at SNR of 10 dB compared to 5 × 10 −4 without optical isolator and 8 × 10 −4 without mode-selective filter. The proposed model reduced the BER by 80 % and intermodal crosstalk by 40–60 % compared to the baseline. The BER decrease from 5 × 10 −4 to 2 × 10 −4 was observed as an SNR gain of 1.2–1.8 dB. The results show performance enhanced propagation efficiency, channel reliability, and physical-layer security, which is suitable for the system to be used in secure optical communication network.