Jun-ichi Kani

Next-generation PON-part I: Technology roadmap and general requirements

Gigabit-class passive optical networks have been standardized and are now being deployed. This article presents possible migration scenarios toward the next-generation PON and proposes a technology roadmap of evolutionary growth (termed NG-PON1) vs. revolutionary change (termed NG-PON2). This article then details the general requirements for NG-PON1 to support various popular applications many service providers expressed interests on as well as to enable smooth migration from Gigabit PON.

Enabling Technologies for Future Scalable and Flexible WDM-PON and WDM/TDM-PON Systems

Wavelength-division multiplexing (WDM) technologies are expected to play a key role in realizing the next generation scalable and flexible passive optical networks (PONs). One candidate is WDM-PON, in which each optical network unit (ONU) uses a different wavelength, i.e., a unique wavelength, in each direction to communicate with the optical line terminal. Another candidate is WDM/time-division multiplexing (TDM)-PON; it combines WDM with TDM technology. This paper reviews recent state-of-the-art research on the enabling technologies needed to realize future WDM-PON and WDM/TDM-PON systems, and discusses future directions toward practical PON systems.

Options for future optical access networks

Optical access technology is now standardized, commercially available, and being deployed in some countries. In general, technology continues to develop, and optical access is no exception. New optical access technologies are now being widely reported; the technical trends are WDM, 10 Gb/s, and longer reach/higher splits. It is also important to take account of the evolution from installed legacy in possible future optical access standards

Impact of backreflection on upstream transmission in WDM single-fiber loopback access networks

This paper investigates the impact of backreflection lights on upstream transmission in wavelength division multiplexing (WDM) single-fiber loopback access networks, where a WDM light source is located at the central office (CO) and each optical network unit (ONU) includes an optical modulator with optical amplifiers. This study considers backreflection lights from two sources, the continuous wave (CW) light at the CO (Reflection-I) and the modulated signal at the ONU (Reflection-II). It is confirmed, for the first time, that the impact of Reflection-II increases strongly with ONU gain. To estimate the impact of these backreflection lights, a simple intensity noise estimation scheme is presented. This scheme clarifies that the acceptable transmission line losses is 10 dB for 1.25 Gb/s under the optical return loss (ORL) of -32 dB.

Optical carrier supply module using flattened optical multicarrier generation based on sinusoidal amplitude and phase hybrid modulation

This paper presents an optical carrier supply module (OCSM) that functions as a common multicarrier light source, a wavelength bank, for superdense wavelength-division multiplexing (SD-WDM) networks that utilize a large number of wavelengths with narrow channel spacing. A novel sideband generator based on a sinusoidal amplitude-phase hybrid modulation scheme is the key technique. The sideband generator generates nine flattened optical sidebands within 3 dB from one seed light source, and the input from wavelength-division multiplexing (WDM) seed carriers expands the number of generated sidebands. Scalability against the number of wavelengths is achieved by increasing the number of seed carriers used. The SD-WDM system employing OCSM reduces the number of laser diodes (LDs) and attendant wavelength monitoring/stabilization circuits. Multiple distributions to SD-WDM networks by splitting the OCSM output can promote this effect. We designed OCSM and experimentally investigated its performance pertaining to the electrical signal-to-noise ratio (SNR) of the OCSM output. The experimental results show the wavelength scalability to 1000 channels. We also developed an OCSM prototype that generated 12.5-GHz-spaced 256-channel WDM carriers. All the generated carriers exhibit the electrical SNR of more than 31.5 dB at 2.5 Gb/s and the power flatness of within 3 dB. The distribution over 100 SD-WDM networks is experimentally confirmed.

Access and metro networks based on WDM technologies

This paper describes the technical issues of access and metro networks based on wavelength division multiplexing (WDM) technologies, some solutions, and an experimental demonstration. A WDM star access network with colorless optical network units (ONUs) is proposed. For realizing the colorless ONU, two approaches are introduced; optical carrier supply and spectrum slicing. In addition, a WDM metro ring network with scalable optical add/drop multiplexers (OADMs), namely the tapped-type OADM, is proposed to effectively accommodate the large amount of traffic issued from access networks. Prototypes are constructed and used to verify the feasibility of the proposed WDM technologies.

Standardization trends and prospective views on the next generation of broadband optical access systems

This paper reviews the major trends in the next generations of optical access systems. The motivations behind the development of advanced systems are presented, and then three major technical areas are explored. First, the field of 10 Gbit/s passive optical network (PON) systems is laid out. Second, the various solutions to long reach PON are reviewed. Third, the very wide and exciting field ofWDMand hybrid WDM-TDMA PONs are discussed. The paper closes with a review of the expected timeline for the standardization of these technologies.

Power Saving Techniques and Mechanisms for Optical Access Networks Systems

This tutorial paper provides an overview of studies and works to address the power saving issue in the optical access network (OAN), which typically comprises passive optical networks (PONs) and Ethernet aggregators (EAs). First, it describes techniques to reduce the power consumption of the optical network unit in each subscribers home. It outlines methods standardized in ITU-T such as “dozing” and “cyclic sleep,” as well as elucidating other techniques. Next, power saving at the optical line terminal (OLT)/EA side is focused. The energy-aware operation of link aggregation and its application to OAN are described to decrease power consumed by the EAs used with time-division multiaccess (TDMA) PONs. Finally, a selective OLT sleep technique is introduced for the next-generation wavelength division multiplexing (WDM)-TDMA PON with wavelength routing technologies.

1-Tb/s (100 x 10 Gb/s) super-dense WDM transmission with 25-GHz channel spacing in the zero-dispersion region employing distributed Raman amplification technology

We achieve 1 Tb/s (100/spl times/10 Gb/s) super-dense WDM (super DWDM) transmission with 25-GHz channel spacing (0.4 bit/s/Hz spectral efficiency) in the zero-dispersion region over a 4/spl times/80 km dispersion-shifted fiber by employing backward pumped distributed Raman amplification and forward error correction. By adopting bi-directional pumping, we present experimental results showing that the transmission distance is extended approximately threefold to 1040 km.

Dynamic TWDM-PON for Mobile Radio Access Networks

In recent years, the diffusion of mobile terminals has brought about an explosive increase in communication traffic of mobile RANs. The number of radio base stations and optical fiber lines between them is becoming larger. For this reason, we studied effective optical network technologies for mobile RANs and propose the use of TWDM-PON as a means of enabling RANs to be operated flexibly and have wideband communication capability. We confirmed the feasibility of TWDM-PON for this application by numerical simulation. The results show that TWDM-PON can accommodate the bandwidth more than TDM-PON and completely eliminate unused bandwidth in TDM-PON.