Passive Optical Network Configuration Research Articles

400-Gbps/80-km Rate-Flexible PCS-64-QAM WDM-CPON With Pseudo-m-QAM Chaotic Physical Layer Encryption

For next-generation high-capacity, rate-flexible, and secure 400-G passive optical network (PON), a scheme joint wavelength division-multiplexed (WDM), entropy-regulated probabilistic constellation shaping-64-quadrature amplitude modulation (PCS-64-QAM) and chaotic encryption mapping, is proposed and demonstrated. For the first time, chaotic encryption is realized over the PCS-based PON with the architecture from one optical line terminal (OLT) to multiple optical network units (ONUs). Chaotic encryption with an initial-value-sensitive feature can generate a large amount of parallel encrypted sequences which provide a key pair corresponding with every possible entropy/rate. A novel mapping from PCS-64-QAM with various entropies to pseudo- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> -QAM is designed, which erases the entropy information of the link and encrypted the original information of the sequence. The encryption transmission is demonstrated over a real-time dual-polarized coherent optical platform with an 80-km link and typically one-to-many PON configuration, and a net 211.80∼348.12-Gb/s rate result within the hard-decision forward error correction (FEC) threshold is achieved for 6λ × 2 ONUs group. The rate of each polarization state can be tuned in a minimum 3.408-Gbps step in the demonstration. Expanding from the basis of the original WDM-CPON, this work prepares an adapted chaotic encryption scheme for large-scale access. Overall, our proposed scheme can provide an abundant system loss budget, a large rate tunable range, and basic physical layer security for next-generation rate-flexible coherent PON (FLCS-CPON).

Optical Power Budget of 25+ Gbps IM/DD PON with Digital Signal Post-Equalization

While infrastructure providers are expanding their portfolio to offer sustainable solutions for beyond 10 Gbps in the access segment of optical networks, we experimentally compare several modulation format alternatives for future passive optical networks (PONs) aiming to deliver 25+ Gbps net-rates. As promising candidates, we consider the intensity modulation direct detection (IM/DD) schemes such as electrical duobinary (EDB) and 4-level and 8-level pulse amplitude modulations (PAM-4/8). They are more spectrally efficient than the conventional non-return-to-zero on-off-keying (NRZ-OOK) used in current 10G PONs. As we move to higher rates, digital equalization enhances the performance by smoothening the systems imperfection. However, the impact that such equalization has on the optical power budget remains unclear. Therefore, in this article, we fairly compare the optical power budget values of a time division multiplexed PON (TDM-PON) exploiting a linear digital signal equalization at the receiver side. We consider the conventional PON configuration (20 km of single-mode fiber (SMF), 1:N optical power splitting) with IM/DD and net-rates above 25 Gbps. Furthermore, we focus on a downstream transmission imposing the bandwidth limitations of 10G components using a digital filter before the detection. The obtained results show that the use of a digital post-equalization with 43 feed-forward (FF) and 21 feedback (FB) taps can significantly improve the signal quality enabling new alternatives and enhancing the optical power budget.

Performance analysis of OCDMA PON configuration supporting multi-rate bursty traffic with retrials and QoS differentiation

An Optical Code Division Multiple Access (OCDMA) Passive Optical Network (PON) is a highly promising PON configuration, thanks to the potential of OCDMA technology in eliminating channel contention and efficiently supporting multi-rate traffic with different QoS requirements. In this paper, we provide a mathematical framework for a call-level performance analysis of an OCDMA PON that accommodates multiple service-classes of bursty traffic with retries. Blocked calls of random arrivals may immediately retry several times, by requesting less resources (number of codewords) each time, in order to be admitted for service. The bursty nature of traffic is denoted by the fact that in-service calls may alternate between transmission and no-transmission periods. Our analysis takes into account user activity and the various components of additive noise. An approximate recursive formula is derived for the efficient calculation of call-level performance measures. The proposed analytical model is further extended to assess the performance of an OCDMA PON that provides QoS differentiation, through the utilization of multiple-weight optical codes. Both proposed models are verified through simulation and found to be absolutely satisfactory. Moreover, comparison of the new models with a model without retries shows the necessity and effectiveness of the new models.

Reliability implications of using LIGA components in communication networks

This paper examines the potential reliability implications of using LIGA components in communication networks. In particular, it focuses on fibre optic-based systems and the reliability issues that need to be addressed if LIGA technology is to become an integral part in the development of Passive Optical Networks (PONs). The paper briefly describes a typical PON configuration, gives a basic overview of the concepts used to assess system reliability and discusses the importance of accelerated testing and computer modelling to predict system performance.

An evaluation of architectures incorporating wavelength division multiplexing for broad-band fiber access

Wavelength division multiplexing (WDM) offers the potential to transport very high bit rates in access systems serving residential and small business customers. We describe the options for WDM access systems, and evaluate them on the basis of an international standard that is emerging for passive optical networks (PONs) that use wavelength-independent power splitting. The greatest impediment to meeting the high-bandwidth potential of WDM for downstream (i.e., from the central office to the home) transmission is the need for a moderately priced multiple-wavelength light source, implementing WDM in the upstream (home to central office) direction presents greater hurdles than in the downstream. The technical aspects of overcoming these hurdles can all be met. The real challenge will be in finding technical solutions that can meet the very stringent cost requirements of access systems. Systems that use WDM in the downstream direction only, while using wavelength-independent power-combining in a PON configuration for upstream, may prove economical before full WDM systems. WDM may also prove valuable if upgrades are needed in the future for power-splitting PON's.

Design and fabrication of monolithically integrated DFB laser-wavelength duplexer transceivers for TPON/BPON access links

The fabrication and characterisation of monolithically integrated OEIC transceivers for use in optical subscriber access links are reported. A design incorporating DFB lasers, wavelength duplexers and a monitor photodiode, specific to the TPON/BPON passive optical network configuration is presented.