SOA Amplified 100 Gb/s/λ PAM-4 TDM-PON Supporting PR-30 Power Budget with >18 dB Dynamic Range

Abstract

Semiconductor optical amplifier (SOA) is considered an excellent candidate for power amplification at O-band due to its low cost and small footprint. In passive optical networks (PONs), SOA is popular as a booster and pre-amplifier to improve the link power budget. However, whether as a booster or pre-amplifier, SOA will induce different degrees of nonlinearity when the output power is high, which degrades the transmission performance of the system and leads to a limited receiver dynamic range. In this paper, we experimentally demonstrate the feasibility of using SOA in both transmitter and receiver sides for power budget improvement in 100 Gb/s/λ four-level pulsed amplitude modulation (PAM-4) time division multiplexed PON (TDM-PON) system at O-band. For compensating the linear and nonlinear impairments induced by transceivers and SOA, a look-up-table (LUT) pre-compensation at the optical line terminal (OLT) side and a simple feed-forward equalizer (FFE) at the optical network unit (ONU) side are adopted for downstream transmission. For upstream transmission, a 2nd-order Volterra nonlinear equalizer (VNLE) is utilized at the OLT side, and no pre-compensation is used at the transmitter of the ONU, which releases the digital signal processing (DSP) pressure of ONUs in a multi-user scenario. For the soft-decision FEC (SD-FEC) threshold (1 × 10−2), the IEEE PR-30 power budget requirement is met, and >18 dB dynamic range is achieved in both 25 km downstream and upstream transmission.

High Dynamic Range 100G PON Enabled by SOA Preamplifier and Recurrent Neural Networks

“…To meet the HS-PON 29 dB optical loss budget using 100Gb/s PAM4, SOA preamplifiers combined with photodiodes have been proposed for the OLT [7]. However, the 19.5 dB PON dynamic range requirement will mean SOA preamplifiers potentially operating in the gain-saturated regime of the SOA for high-power, loud bursts, leading to non-linear patterndependent distortions of the modulated signal, known as patterning.…”

“…Neural Network Equalisers (NNEs) have been proposed as a solution to SOA non-linearities for future PON systems [9], [11], while Volterra equalisers are a competitive alternative, which are also non-linear [7], [16]. However, these mostly focus on achieving the optical loss budget set out in HS-PON, and DR considerations are not discussed.…”

“…Compared to non-return-to-zero (NRZ) modulation, PAM4 is an attractive solution due to its reduced electro-optic bandwidth requirements, albeit at the cost of reduced receiver sensitivity. In order to boost sensitivity and achieve the 29 dB optical loss budget, Semiconductor Optical Amplifiers (SOAs) can be used as receiver preamplifiers, and have gained widespread interest for IM/DD PON since they are readily integrable, can operate in the C-and O-bands, and are relatively low-cost [7], [8]. However, the impact of SOA nonlinearities such as the gain saturation-induced patterning effect is a concern, especially in PON upstream transmission due to the large loud-soft packet Dynamic Range (DR) inherent to PON burst-mode signalling.…”

“…Work has previously focused on achieving the 29 dB optical loss budget, such as in [12] where recurrent neural networks are used in conjunction with an SOA preamplifier to realise a 30 dB loss budget for 100 Gb/s PAM4. However, the implications of the challenging 19.5 DR requirement have also drawn the attention of researchers using non-ML techniques, as in [13] where the authors investigate a look-up table pre-compensation technique on the transmitter side, and [7] which implements a non-linear Volterra equaliser (VNLE) to overcome SOA non-linearities and achieve 18 dB DR for 100 Gb/s PAM4. In this work, we will use VNLE as a performance and complexity benchmark, since it is a popular alternative to ML-based equalisers in IM/DD systems and widely researched [14], [15], [16].…”

Key Technologies for a Beyond-100G Next-Generation Passive Optical Network

“…The current works have focused on achieving a 29 dB optical loss budget; for example, in [56,57], a recurrent neural network combined with an optical sensor uses an SOA preamplifier to achieve a 30 dB loss budget of 100 Gbp PAM4. However, the challenge of meeting the 19.5 DR requirement has also brought attention to non-ML technologies, such as in [58], where the authors investigate the transmitter's lookup table pre-compensation technique with a nonlinear Volterra equalizer (VNLE) to overcome the nonlinearity of SOA and achieve up to 18 dB DR for the 100 Gbp PAM4 format. Consequently, burst mode data transmission faces a major challenge in electronic design.…”