El-Nahal, Fady. “Bidirectional OFDM-WDM-PON System Employing 16-QAM Intensity Modulated OFDM Downstream and OOK Modulated Upstream”. Photonics Letters of Poland 8, no. 2 (June 30, 2016): pp. 60–62. Accessed November 23, 2024. http://photonics.pl/PLP/index.php/letters/article/view/8-22.