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Abstract-Energy consumption of customer premises equipment (CPE) in the new generation of time-division multiplexing (TDM) passive optical networks (PON) operating at 10 Gb/s, has become a serious problem both in terms of the global network energy consumption and the CPE battery life. The proposed low energy passive optical network (PON), based on a novel bitinterleaving downstream protocol, reduces the protocol processing energy by a factor of 30 and enables a significant reduction in the total CPE energy consumption over the standard 10 Gb/s PON CPE. The network architecture, protocol and the key enabling techniques for its implementation, including dynamic traffic interleaving, rate-adaptive descrambling of decimated traffic and downsampling clock and data recovery (CDR) circuit, are described. Detailed analysis of the CPE energy consumption and comparison with the standard PON CPE is also included in the paper.

Abstract:A functional demonstration of bit-interleaving TDM downstream protocol for passive optical networks (Bi-PON) is reported. The proposed protocol presents a significant reduction in dynamic power consumption in the customer premise equipment over the conventional TDM protocol. It allows to select the relevant bits of all aggregated incoming data immediately after clock and data recovery (CDR) and, hence, allows subsequent hardware to run at much lower user rate. Comparison of experimental results of FPGA-based implementations of Bi-PON and XG-PON shows that more than 30x energy-savings in protocol processing is achievable.

A novel, low power, downstream clock and data recovery (CDR)-decimator architecture is proposed for next generation, energy efficient 10 Gb/s optical network units (ONUs). The architecture employs a new time division multiplexing (TDM) bit-interleaving downstream concept for passive optical networks (Bi-PON) allowing early decimation of the incoming data and lowering of the processing speed to the user rate of the ONU, thus reducing the power consumption is significantly.Introduction: As the demand for broadband services keeps rising, data-rates in access networks keep increasing. Despite technological improvements, energy consumption in high speed access networks is expected to rise inevitably. Considering the vast amount of subscribers, the total power consumption in the ONUs is of major concern. Presentday ecological awareness, increasing energy costs and thermal concerns require drastic measures to be taken.Because of the very low losses in optical fibers, PON in itself is a very energy-efficient technology. Standard downstream time division multiplexing PON (TDM-PON) protocols, however, are inherently energyinefficient as they operate on frame-level. This requires an ONU to process every frame header at the aggregated line-rate, even though the majority of the packets are intended for other users. Data within frames has to be processed at full line-rate speed until the ONU determines its designated receiver. In conventional TDM-PON, a burst-mode transmission operation is used in the upstream direction. Its operation is relatively more energyefficient than the downstream direction because of its inherent load dependency.Both ITU-T and IEEE have recently opened the discussion on the energy-saving potential of PONs [1][2][3][4], which led to intensive research to address this problem [2][3][4][5]. Thus far, the attention is mostly focussed on the possibility of introducing sleep mode techniques into the standard PON systems. Ideally an ONU with sleep mode support would only be awake during reception of its own payload. Practically, however, non-negligible sleep/wake transition times [2] and quality of service (QoS) requirements [3] limit the efficacy of these techniques.Theoretically, the lower limit for the power-consumption in ONUs is dictated by the actual user-rate, which typically is a fraction of the aggregated line-rate. While conventional TDM-PON protocols are inherently operating at line-rate, the proposed bit-interleaving CDR (Bi-CDR) takes advantage of the line-rate -user-rate discrepancy. In every frame period, the Bi-CDR decimates and offsets the downstream payload reception based on Bi-PON frame header information. Because the interleaving takes place on bit-level, the bits intended for a specific user are uniformly spread in time. This allows ONUs to sample data at their own respective user rate. In this way, downstream bandwidth is dynamically allocated through header information, preceding the encapsulated bitinterleaved payload.