A reflective coherent orthogonal frequency-division multiple-access (OFDMA) passive optical network (PON) based on differential amplitude and phase-shift keying (DAPSK) OFDM is proposed herein. In the conventional OFDMA-PON uplink transmission, each optical network unit (ONU) signal has different channel and phase-noise characteristics. In addition, each ONU has an independent laser source; therefore, the carrier frequency offset (CFO) differs among the ONUs. These multiple noises worsen as the number of ONUs increases and adversely affect the spectral bandwidth and system complexity. The proposed system using reflective-type ONUs avoids multiple CFOs because every ONU shares the same laser source, which is transmitted from an optical line terminator. Moreover, by applying a differential modulation scheme to OFDM, we resolve the multiple channel and phase noises without spectral efficiency loss and system complexity increase. The spectral efficiency is maximized using an adaptive modulation technique. The proposed system is experimentally demonstrated in a 20-km OFDMA-PON uplink transmission link with two reflective ONUs. The results confirm the possibility of uplink multiple access without multiple-noise compensation processes. The optimal spectral efficiency in terms of bandwidth size and number of subcarriers is analyzed.
Bibliographical noteFunding Information:
Manuscript received May 8, 2018; revised July 27, 2018; accepted October 2, 2018. Date of publication October 8, 2018; date of current version November 2, 2018. This work was supported by the ICT R&D program of MSIP/IITP, Republic of Korea (2014-3-00538, Next-generation coherent optical access physical network). (Corresponding author: Sang-Kook Han.) The authors are with the Department of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea (e-mail:,firstname.lastname@example.org; email@example.com; firstname.lastname@example.org).
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics