Flexible Filter Bank Multi-Carriers PON Based on Two-Dimensional Multiple Probabilistic Shaping Distribution

Gigabit-capable Passive Optical Network (PON) systems, such as GPON (standardized in ITU-T Rec. G.984 series) and 1G-EPON (IEEE 802.3ah, now part of IEEE 802.3-2008) have been standardized and are now being mass-deployed in various markets around the world. With the continuous increase in bandwidth demand generated by consumer and business applications, the need for a new, higher capacity access architecture is more than obvious. Therefore, one of the principal requirements for next-generation PON (ngPON) is to provide a substantial increase of the bandwidth available to end-subscribers, when compared with GPON and 1G-EPON. Additionally, considering the Capital Expenditure (CAPEX) investment made for deploying gigabit-capable PON systems, ngPON must be able to protect the investment of the legacy networks by ensuring a subscriber seamless migration from GPON/1G-EPON to ngPON. ngPON systems are currently under standardization in two Standard Development Organizations (SDOs), i.e. 10G-EPON in IEEE, as part of P802.3av, and NG-PON in FSAN/ITU-T. The IEEE P802.3av standard focuses only on extensions to the existing 1G-EPON specifications in order to support 10Gbit/s operation, including symmetric and asymmetric data-rates. On the other hand, NG-PON recommendations cover the complete system, starting from Physical Medium Dependent (PMD), followed by framing and medium access, and ending with security and service provisioning mechanisms. NG-PON systems are divided into two major groups, i.e. NG-PON1 and NG-PON2, based on their characteristics of co-existence with legacy GPON systems. Other SDOs focus on operational, architectural, and management aspects of the existing and future PON systems, e.g. BroadBand Forum (BBF, former DSL Forum).

Future passive optical network (PON) systems supporting more than 50 Gb/s/λ present a challenge for the use of intensity modulation direct detection (IM-DD). Since coherent technology improves the receiver sensitivity over that of IM-DD, it is a promising candidate for 100 Gb/s or higher PON systems. Introducing hardware-efficient signal processing technologies tailored to PON systems will help render coherent technology suitable for PON systems. We here review hardware-efficient signal processing technologies suitable for PON systems. We introduce two types of simplified adaptive equalization (AEQ), one which sacrifices differential group delay compensation (DGDC), and another which sacrifices some chromatic dispersion compensation but does provide DGDC. Transmission experiments on a 100 Gb/s/λ-based coherent wavelength division multiplexing (WDM) PON system showed that simplified AEQ without DGDC and with DGDC exhibited only 0.2 and 1.4 dB penalty, respectively, compared with conventional DSP. The additional penalty due to the maximum possible cumulative DGD was evaluated by numerical simulation. Conventional AEQ and the simplified AEQ with DGDC showed negligible penalty, but the simplified AEQ without DGDC showed a 1.4 dB penalty. We also introduce simplified carrier phase recovery (CPR) with interpolarization phase offset estimation, and this showed the same performance as the conventional DSP, in both experiment and simulation. Taking these results into account, 100 Gb/s/λ-based coherent WDM PON systems with the simplified AEQs in combination with the simplified CPR were shown to be able to support the loss budget required for eight ONU splits over an 80 km span of single mode fiber.

In order to realize receiver (Rx) photonic integrated circuits (PICs) applicable to 400 Gb/s-class coherent passive optical network (PON) systems, we integrated tunable wavelength f ilters (TWFs), PIN photodiodes (PIN-PDs), and optical 90 degree hybrids (90HBs) into Rx PICs fabricated on a commercial standard silicon photonics (SiPh) platform. As a result of device evaluation, we observed characteristics indicating the potential for application in 400 Gb/s-class coherent PON systems. Subse quently, we prototyped Rx assemblies in which the Rx PIC and a digital signal processing (DSP) chip are mounted. When the Rx assembly received a 60-Gbaud dual-polarization (DP) quadrature phase shift keying (QPSK) 200 Gb/s C-band optical signal after 2 km loopback transmission, we achieved an optical received power of −24 dBm at a bit error ratio (BER) of 2×10−2, which corresponds to the forward error correction (FEC) limit. Based on this result, the Rx assembly is suitable for a PON system with a maximum transmission distance of 20 km and up to 16 terminations. Similarly, when the Rx assembly received a DP 16 quadrature amplitude modulation (QAM) 400 Gb/s optical signal, we achieved an optical received power of −6 dBm at the FEC limit. Although some issues remain, these results suggest the Rx assembly can be applied to 400 Gb/s-class coherent PON systems. In the future, we will improve the Rx characteristics by reducing insertion loss of the Rx PICs and will prototype and evaluate transmitter (Tx) assemblies.

This paper proposes a cyclic sleep control scheme on the basis of the queue length (QL) information for energy-efficient passive optical network (PON) systems to cope with diversified quality-of-service (QoS) requirements. Cyclic sleep control is an effective power-saving technique for optical network units (ONUs) in PON systems. In conventional controllers based on the frame inter-arrival time (FIAT) information, however, downstream queuing delay at an optical line terminal is greatly affected by the amount of downstream traffic. Our proposed QL-based controllers with feedback control techniques, i.e., QL-based proportional and proportional-derivative controllers, effectively reduce the power consumption of ONUs while maintaining the downstream queuing delay at a constant level. The simulation results confirm that the proposed controllers provide better performance than the conventional FIAT-based controller in terms of power consumption and average queuing delay.

This paper proposes a hybrid passive optical network (PON) system based on a dense wavelength division multiplexing-PON (DWDM-PON) and reach extender (RE) for increasing the optical link budget and link capacity in an existing gigabit PON (GPON) system. A DWDM-PON is applied to the feeder fiber and is interfaced with the RE. The RE provides a wavelength conversion between the DWDM-PON and GPON through frame regeneration, and controls upstream burst signals. The hybrid PON system enables a legacy GPON system to operate over a minimum 40 km distance with a 128-way split per WDM wavelength.

We propose and experimentally demonstrate a full-duplex integrated passive optical network (PON) and indoor optical wireless communication (OWC) system. For the PON part, an external cavity laser (ECL) and a directly modulated laser (DML) are used as optical sources for downlink and uplink, respectively. The OWC subsystem utilizes a visible light-emitting diode (LED) for downlink and an infrared LED (IR-LED) for uplink transmission. To enable high spectral efficiency (SE), high-speed transmission, and flexible multiple access with simplified optical network unit (ONU)-side digital signal processing (DSP), multilevel, multiband quadrature amplitude modulation (QAM) and hybrid 128/64/16 Nyquist single-carrier frequency domain equalization (N-SC-FDE) modulation are implemented in this paper. In terms of 62.5 MHz OWC N-SC-FDE signals, the system successfully delivered a further 140 cm indoor distance after transmitting over a span of 25 km standard single mode fiber (SSMF) together with three subbands of 250 MHz PON signals. As a proof of concept, an integrated system of symmetrical full-duplex 5 Gb/s PON and 250 Mb/s OWC at each direction for three wired users and one wireless user is successfully achieved. The measured bit error ratios (BERs) for each user are all smaller than the 7% pre-forward-error-correction (pre-FEC) limit of 3.8 × 10−3, which shows the promising potential and feasibility of this proposal to extend multiple services from metro areas to suburban areas.

This paper reviews the future directions of next generation passive optical networks. A discussion on standardized 10 Gb/s passive optical network (PON) systems is first presented. Next, new technologies that facilitate multiple access beyond 10 Gb/s time division multiple access (TDMA)-PONs will be reviewed, with particular focus on the motivation, key technologies, and deployment challenges. The wavelength division multiplexed (WDM) PON will be discussed and in combination with TDMA, the hybrid WDM/TDMA PON will be reviewed in the context of improving system reach, capacity, and user count. Next, discussions on complementary high-speed technologies that provide improved tolerance to system impairments, capacity, and spectral efficiency will be presented. These technologies include digital coherent detection, orthogonal frequency division multiple access (OFDMA), and optical code division multiple access (OCDMA).

WDM PONs based on colorless technology

This chapter focuses on general passive optical network (PON) topics and technologies that are largely independent of the specific PON protocol. These topics include an introduction to PONs, technology challenges, system powering issues, and protection for survivability. A PON system consists of a passive fiber tree/bus network that connects multiple optical network terminals (ONTs) to a single optical line terminal (OLT) optical transceiver. PON systems typically transmit both upstream and downstream data over the same fiber. The first generation of PONs was based on time domain multiple (TDM) signals such as DS1/E1 signals. The second generation of PONs was based on Asynchronous Transfer Mode (ATM). PON is increasingly used for connections to enterprise customers and wireless base stations. There are several different parts of the PON system to consider for protection. The chapter discusses these aspects of PON protection.

We address the development of mobile fronthaul (MFH) radio-over-fibre (RoF) transceivers with the capability to transport Digital RoF (D-RoF) signals for C-RAN applications. The coexistence of transport of D-RoF with legacy and the future Passive Optical Network (PON) systems, such as Next Generation PON 2 (NG-PON2) will be analysed. The preliminary experimental results of transmitting several D-RoF signals with high spectral efficiency and based on Sub-Carrier Multiplexing (SCM) techniques will be presented.

Optical fibers are a key inventive discovery that contributed to the digital revolution, although cost becomes a major factor for long-distance communication. Whereas passive optical networks (PONs) offer reduced costs and cater to multiple users; hence, they are becoming more common in LANs, densely inhabited areas, and backbone networks. Numerous experiments on PON systems have been authored in the last couple of years, with results expressed in terms of BER, eye openings, quality of received bits factor, signal-to-noise ratio (SNR), and burst blocking, which demands a vast review of PONs based on these parameters. So, a comprehensive review of PONs is extensively researched to identify the methods’ limitations. Along with long-reach(LR)-PON systems, power conservation in PONs and burst contention are also addressed. To demonstrate the performance of PON architectures, the findings are provided in terms of delay, energy efficiency, and operations intensity.

We propose and experimentally demonstrate a novel integrated passive optical network (PON) and indoor visible light communication (VLC) system based on Nyquist single carrier frequency domain equalization (N-SC-FDE) modulation with direct detection. In this system, a directly modulated laser and a commercially available red light emitting diode are served as the transmitters of the PON and VLC, respectively. To enable high spectral efficiency, high-speed transmission, and flexible multiple access with simplified optical network unit-side digital signal processing, multilevel, multiband quadrature amplitude modulations 128/64/16 are implemented here. VLC N-SC-FDE signals are successfully delivered a further 30 cm indoor distance after transmitting over a span of 40 km single mode fiber (SMF) together with 3 sub-band PON signals. As a proof of concept, a 10 Gb/s PON and 500 Mb/s VLC integrated system for three wired users and one wireless user is successfully achieved, which shows the promising potential and feasibility of this proposal to extend multiple services from metropolitan to suburban areas.

A light source centralized bidirectional passive optical network (PON) system based on multiband direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) downstream and quadrature phase-shift keying (QPSK) upstream is experimentally demonstrated. By introducing a simple optical single-side band (SSB) filter at the optical network unit (ONU), all the desired signal bands will be immune from the deleterious signal-signal beating interference (SSBI) noise with only single-end direct-detection scheme. An adaptive modulation configuration is employed to enhance the entire downstream throughput which results in a 150-Gbps downstream data rate with a single optical carrier. In the upstream direction, by recycling the clean downstream optical carrier, a 12.5 Gb/s QPSK format with coherent receiving mechanism in central office is adopted for better receiving sensitivity and dispersion tolerance. With the power enhancement by the long-reach PON architecture, the downstream splitting ratio can achieve as high as 1:1024.

A passive optical network (PON) architecture based on a hybrid wavelength-division multiplexing (WDM) and time-division multiplexing (TDM) PON system with a remotely pumped erbium-doped fiber amplifier (EDFA) is presented as an excellent candidate for use in a next-generation optical access network. The remotely pumped EDFA operates as a bidirectional amplifier and provides a 15-dB gain to both upstream signals and seed light sources, so the sensitivity of upstream transmission is greatly improved. An upstream transmission of 1.25 Gb/s with a low seed channel power of -14 dBm is made feasible over a total reach of 25 km for 32-WDM channels and 16-TDM splits by the use of the remotely pumped EDFA. This scheme has advantages that it uses a single transmission fiber for both down-and up-stream signals and that it reduces the Rayleigh scattering contribution.

Efficient bandwidth allocation scheme for PON system enabling LAN emulation