Achieving 1024 Subscribers in XG-PON via a Bidirectional Optical Amplifier

1024 subscribers in the 10-gigabit-capable passive optical network (XG-PON) are achieved using a bidirectional optical amplifier. It consists of an erbium doped fiber amplifier (EDFA) and a semiconductor optical amplifier (SOA) for 9.9532 Gbps downstream data at 1577 nm and 2.4883 Gbps upstream data at 1270 nm, respectively. The power budget is estimated for our XG-PON link using commercial optical line terminal (OLT) and optical network unit (ONU), 20-km standard single mode fiber (SSMF), 1:1024 optical splitters, a polarization controller (PC) and our bidirectional amplifier, including all important parameters and specifications. The gains of EDFA and SOA are measured versus input power by an optical spectrum analyzer (OSA), as well as the amplified spontaneous emission (ASE) noise powers to approximate the amplifier’s noise figure (NF). Different setups of downstream and upstream transmissions are experimented to study the effects of chromatic dispersion (CD) from 20-km SSMF and the added ASE noises from EDFA and SOA. Their corresponding curves of bit error rate (BER) and data eye diagrams are analyzed. Comparing the power penalties at same 10^-6 BER, a total 0.69-dB penalty in downstream data is mainly caused by the CD impairment from 20-km SSMF, whereas a total 4.39-dB penalty in upstream data is dominated by the severe ASE noise from SOA. Also, the eye diagram shows that this noise is radically reduced by the limiting amplifier (LA) inside OLT and ONU optical transceivers. The 1-hour nonstop bidirectional data transmissions over our XG-PON link prove an error-free transmission in downstream and BER = 3.64×10^-5 in upstream, less than the maximum 1.8×10^-4 BER in XG-PON standard. Thus, the error-free bidirectional data transmission can be accomplished.