Search

The passive optical network (PON) is widely deployed in access networks, and various specifications have become standards designed to meet demands of each market. To accelerate new PON-based service creation, software-defined network enabled broadband access (SEBA) is being studied; it uses a common API to abstract various optical line terminal (OLT)/optical network units (ONUs) and manages the devices via a controller. However, the current abstraction unit in SEBA supports only ITU-T PON. In order to support IEEE PON, multiple package types and switching management functions must be considered. This paper proposes a technology profile including package types for IEEE specification and an adapter that abstracts IEEE PON and switches functions according to the specified package type. The logical link configuration settings for ITU-T PON and IEEE PON are implemented in common, and the adapter abstracts IEEE PON OLT/ONU by switching between extended operation, administration, maintenance (eOAM) functions for package B and other eOAMs. We demonstrate the proposed software on a system implemented using commercially available OLT/ONU and OSS in SEBA. The results show that OLT/ONUs can be managed via a common API, differences in package types can be abstracted by technology profiles and our adapter, and that a common SEBA platform can manage, in a unified manner, both ITU-T PON and IEEE PON.

This article proposes a novel architecture of a time division multiplexing passive optical network (TDM-PON) system with general-purpose hardware. The system operates with the point-to-point (P2P) Ethernet protocol and software processing. The architecture is redesigned from the ground up, differing from conventional PON system architectures. In recent years, researchers have attempted to softwarize a number of PON functions such as media access control (MAC) and physical functions, which run on a general-purpose central processing unit (CPU). On the other hand, these existing systems still required PON-dedicated or programmable hardware for processing the PON specific protocol. This paper proposes a TDM-PON system that requires only general-purpose hardware; a network interface card with the use of the P2P Ethernet protocol and a general-purpose server with the use of software processing. To operate the proposed system, we newly developed burst-mode operation and multipoint MAC control schemes, while taking Link Fault Signaling and CPU processing jitter into account. We quantitatively evaluated the burst-mode transmission with P2P generic Ethernet TRx as a preliminary experiment, which showed that Ton and Toff were 75 μs and less than 1 μs, respectively. Then, we measured our developed prototype system's performance for verifying the feasibility of our proposal. In specific, it achieved a 5.2 Gbps PON system consisting of an optical line terminal (OLT) server and two optical network unit (ONU) servers under the condition of a 500-ms grant cycle including a 100-ms discovery window.

This paper summarizes our studies on the flexible access system architecture (FASA), which will support a wide range of services and stimulate the creation of new services in the next generation. After reviewing related concepts and technical trends, FASA's concept and use cases are introduced. FASA aims to cover residential, enterprise, and mobile backhaul/fronthaul services. The technical directions associated with implementing FASA and the challenges raised are described. They include hardware design to maximize the use of common hardware, clarification of architectures that suit time-critical applications, and deeper softwarization.

This paper shows the concept of the elastic lambda aggregation network (EλAN) that will achieve an elastic common access infrastructure for the metro-access network. It proposes a service restoration technique that uses optical path switching and intercentral office handover for EλAN to recover from disasters. The feasibility of the proposed service restoration technique is successfully demonstrated for the first time by using a prototype testbed of a metro-access network. By applying both orthogonal frequency division multiplexing and adaptive modulation, the system automatically changes the transmission parameters (modulation level, the number of subcarriers, and symbol rate) according to the service requirements and conditions of the optical distribution network, such as the link's end-to-end optical loss, in order to achieve accommodate multiple services. In the experiment, an optical network unit in a faulted system automatically reconnected within 10 s to another office 20-km away with the same throughput.

Passive optical networks (PONs) are widely deployed worldwide as access networks, and various standards have been created to serve the demands of different markets. In recent years, software-defined-network-enabled broadband access (SEBA) has been studied for the realization of flexible and cost-effective PONs, while the zero touch provisioning (ZTP) function of optical line terminals (OLTs) and optical network units (ONUs) is being studied for automatic management. However, although ZTP for ITU-T standards has already been implemented, ZTP for IEEE standards has not been achieved, since the workflow is significantly different for each access standard due to differences in the authentication method. The subdivided package specifications and medium access control (MAC) dress authentication are barriers that hinder achieving ZTP for the IEEE standards. This paper proposes a workflow driver based on a model that implements authentication compliant with IEEE PON packages A and B according to events produced by SEBA components and specification information obtained from OLT profiles. The feature of our proposal is to fabricate an IEEE-compliant driver package that automatically switches the authentication method by acquiring the technology profile of the orchestrator, and as soon as IEEE802.1X authentication or MAC address authentication is completed, the subscriber setting is registered to the SDN controller in order to enable data plane service. We demonstrate the proposed workflow driver on a system consisting of SEBA-focused commercially available OLT/ONU hardware and open source software. The results show that the orchestrator can automatically provision ONUs and that managing various access devices on a common access platform is feasible.

This paper presents the world's first field trial of a 40-km reach and over 512-split symmetric-rate 40-Gbit/s λ-tunable time and wavelength division multiplexing passive optical network (TWDM-PON) that utilizes our newly developed high-speed λ-tunable optical network unit transceivers and automatic gain controlled semiconductor optical amplifier-based PON extender for repeater and central office use. The upstream signals for C-band and downstream signals for L+-band in our developed λ-tunable TWDM-PON comply with the wavelength plan of ITU-T G.989 series. In a field trial, we successfully demonstrate error free λ-tunable transmission for the 40-km reach and 1024-split (maximum number) symmetric-rate 40-Gbit/s λ-tunable TWDM-PON over installed standard single-mode fiber links, and advanced network functions such as dynamic load balancing, incremental system upgrade, optical subscriber unit protection, and OLT equipment power saving are also confirmed.

The dis-aggregated passive optical network (PON) optical line terminal (OLT) architecture is attracting attention in academia and industry. This paper first reviews the evolution in dynamic bandwidth allocation (DBA) dis-aggregation. We further enhance the scalability of the dis-aggregated PON-OLT by reducing the bandwidth overhead of REPORT/GATE, the time division multiplexing (TDM) control information transferred between dis-aggregated DBA and the hardware platform. Our experiment verifies that the data compression based on basic integer coding can improve the scalability by 27% with acceptable processing time.

This paper discusses the future direction of optical access networks and proposes a new optical access architecture that will support the evolution of optical access systems from a fiber-to-the-home infrastructure to a common optical access platform that connects various devices and systems to anywhere they want to reach. We describe two technologies for its implementation. One is “modularization,” which is expected to be realized before 2030, and the other is “full softwarization,” which is the longer-term goal of drastically increasing network flexibility. For each technology, we summarize related technical trends and discuss a reasonable system configuration focusing on the access nodes.

We propose a new automation concept for access network equipment called “Plug & Provision.” This concept aims at reducing the workload in provisioning passive optical network (PON) service by utilizing a modular optical line terminal (OLT) and automating the setup sequence. To realize this concept, the automation platform must automatically detect the modular OLT plugged into a switch port and execute the configuration sequence that it triggered. We utilize open-source software in the control/management layer, especially focusing on OpenFlow as a control protocol. We present the overall architecture including a newly proposed PON abstraction and in-band control method for deeply disaggregated modular OLTs, and we demonstrate the feasibility of the architecture.

We propose a new optical access network concept named “Mini-PON.” This concept features the separation of passive optical network (PON)-optical line terminal (OLT) functions into micro module-type hardware that offers switch port pluggability and minimal modular software running on a server to literally minimize the space needed for PON deployment, giving more flexibility to operators who want to deploy PONs in various fields quickly and cost effectively. We explore the optimal function split between hardware and software to balance performance and flexibility. A prototype demonstrates that the proposed implementation architecture can perform as well as a conventional PON in terms of throughput and upstream latency, while also realizing (i) dynamic bandwidth allocation softwarization and modularization via standards-based application programming interfaces and (ii) remote placement of the hardware module from the central office on which the OLT software runs: both are key advances.

This paper summarizes our studies on the Flexible Access System Architecture (FASA) which will support a wide range of services and stimulate new services in the next generation; its overview and technical challenges are described.

The first demonstration of the service restoration technique for metro-access networks successfully shows that ONU accommodated by the disaster-stricken central office is automatically reconnected within 10 sec to another office 20-km away with the same throughput as before disaster.

To quickly meet the diverse requirements imposed by emerging new services on optical access networks, we recently proposed the new concept of "flexible access system architecture" (FASA), which features the disaggregation of time-critical applications. This paper introduces our activities on FASA along with related technical trends. As our key ongoing challenge, the modularization of the dynamic bandwidth assignment function in a passive optical network is reviewed, and information on its use cases, approach, and sequences is given. Furthermore, a reference hardware implementation of FASA for mobile service is described.

This paper presents a λ-tunable optical network unit (ONU) burst-mode transmitter (B-Tx) with high output power and low burst-off-level power for high-splitnumber time and wavelength division multiplexing passive optical networks (TWDM-PONs). The proposed ONU B-Tx utilizes a burst-mode booster semiconductor optical amplifier (SOA) with a control technique for reverse bias voltage that creates an optical power absorption effect in the burstoff- level state. This paper introduces the design of the biasvoltage- state control circuit, simulations of control-circuit operation, evaluations of the static optical power-absorption effect, and burst-mode operation performance in the booster SOA operated by reverse bias voltage. High output power of over +7.4 dBm and low burst-off-level power of under −73.4 dBm∕15 GHz are successfully achieved in all upstream channels. Crosstalk penalty measurements confirm a very low penalty of under 0.1 dB, which leads to a 256 splitnumber TWDM-PON.

In-service wavelength tuning at ONUs provides advanced-network functions of dynamic wavelength allocation (DWA) in WDM/TDM-PONs. Based on DWA usage cases, we present a hitless l-tuning sequence and backup wavelength pre-assignment as keys in next-generation multi-service convergence access networks.

We propose and demonstrate an optical path protection that offers FEC switching function for WDM/TDM-PON with ring topology. A system demonstration confirms proposed automatic wavelength and FEC switching enables a 30km difference of redundant optical path in ring access networks.

More than +6 dBm output power OLT/ONU transceivers which comply with the wavelength allocation plan of the next-generation passive optical network stange2 (NG-PON2) standard (ITU-T G.989.2) are successfully demonstrated thanks to a newly developed semiconductor optical amplifier (SOA) — integrated transmitter.

We propose a burst-off-level power reduction technique for a burst-mode booster SOA implemented λ-tunable transmitter. A large power reduction of 8.2 dB and a low crosstalk penalty of

We introduce the world's first field trial of a symmetric-rate 40-Gbit/s λ-tunable WDM/TDM-PON that uses a high-speed λ-selective ONU TRx and optical extender. 40-km reach and 1024-split λ-switching transmission, and system demonstrations are successfully performed.

In this paper, fairness-aware dynamic subcarrier allocation (DSA) in a distance-adaptive modulation orthogonal frequency division multiple access passive optical network (OFDMA-PON) is proposed and experimentally demonstrated for elastic lambda aggregation networks (EXANs). By applying the distance-adaptive modulation function to OFDMA-PONs, the system can change the transmission parameters (modulation level and symbol rate) for each user according to the user's end-to-end optical loss, which will yield additional bits. Meanwhile, by applying our proposed DSA algorithm, which allocates sub-carriers to users based on transmission parameters and traffic demands, the additional bits can be shared by all users in a fair manner regardless of a user's end-to-end optical loss. This paper conducts a real-time demonstration using an optical coherent OFDMA transceiver and a medium-access control board. The experiments confirm that our algorithm can greatly improve fairness in terms of frame loss rate among users compared to fixed sub-carrier allocation.

We propose a high-output power λ-selective transmitter utilizing a simple configuration burst-mode booster SOA with gain peak detuning that achieve pattern effect mitigation. We successfully demonstrate over 40-dB loss budget and 40-km reach WDM/TDM-PON.

We demonstrate an approach to enhance the optical frequency domain reflectometry (OFDR)-optical coherence tomography (OCT) sensitivity using a semiconductor optical amplifier (SOA) and a superstructure grating-distributed Bragg reflector (SSG-DBR) laser. We find that the sensitivity of the OCT images of an extracted canine tooth increases as a function of SOA injection current due to amplification through stimulated emission. At the injection current of 150 mA, the sensitivity of the OCT image is increased to a factor of 22.8 dB when compared to the unamplified OCT. Furthermore, an 18 µm axial resolution of the OCT in dental tissue is achieved using the discrete wavelength-swept SSG-DBR laser with an axial scan rate of 0.25 kHz. The observed results suggest that the optical amplification by SOA can significantly enhance the sensitivity of the OFDR-OCT system with a high-resolution.

We propose a λ-selective burst-mode transceiver with 100-ns wavelength switching for the use in C and L-bands for upstream and downstream signals, respectively. The bidirectional 40-km transmission of symmetric 40-Gbit/s λ-tunable WDM/TDM-PON is demonstrated without a PON repeater.