Masamichi Fujiwara

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.

12.5 GHz spaced 1.28 Tb/s (512-channel x 2.5 Gb/s) super-dense WDM transmission over 320 km SMF using multiwavelength generation technique

We achieve a 512-channel super-dense wavelength-division-multiplexing (WDM) transmission with a 12.5 GHz channel spacing over 320 km (80 km/spl times/4) of standard single-mode fiber in the C+L-bands. Optical carrier supply modules, which are based on a flattened sideband generation scheme, are applied to generate the 512 wavelengths from only 64 distributed-feedback laser diodes with a frequency spacing of 100 GHz. Arrayed-waveguide gratings with a 12.5 GHz spacing are used in this super-dense WDM experiment.

Application of super-DWDM technologies to terrestrial terabit transmission systems

This paper describes application areas, elemental technologies, and the feasibility of terrestrial terabit wavelength division multiplexing (WDM) transmission systems based on super-dense wavelength division multiplexing (DWDM) technologies with a channel spacing of 12.5 GHz. Numerical simulation results quantitatively show that the merit of super-DWDM transmission is the elimination of the need for dispersion compensation over the several hundreds of kilometers of standard single-mode fiber (SMF). To support super-DWDM transmission, the prototype of a multiwavelength generator, which consists of just an intensity modulator and a phase modulator, is developed as a small-size WDM light source with high-wavelength stability. We use this prototype to conduct a 1.28-Tb/s (512 channels /spl times/ 2.5 Gb/s) transmission experiment with a channel spacing of 12.5 GHz over 320 km (80 km /spl times/ 4 span) of standard SMF without dispersion compensation. The potential and the feasibility of super-DWDM transmission with a channel spacing of 12.5 GHz for terrestrial systems is confirmed by the numerical simulation and the transmission experiment.

Field Trial of 100-km Reach Symmetric-Rate 10G-EPON System Using Automatic Level Controlled Burst-Mode SOAs

This paper reports the worlds first field trial of a 100-km reach symmetric-rate ten gigabit Ethernet passive optical network (10G-EPON) system that uses optical-amplifier-based PON repeaters. Semiconductor optical amplifiers (SOAs) are utilized to handle the 10G-EPON wavelength allocation defined in IEEE802.3av; a fast automatic level control technique is applied to cascaded SOAs for upstream amplification to achieve high gain and wide input dynamic range. An electronic dispersion compensation technique is also applied for downstream detection. These techniques support a 79.5-dB loss budget and 100-km reach transmission with 40 km span lengths. In a field trial, we successfully demonstrate bidirectional real-time uncompressed high-definition television signal transmission over installed standard single-mode fiber links.

Burst-mode compound optical amplifier with automatic level control circuit that offers enhanced setting flexibility in a 10 Gb/s-class PON

Proposed amplifier provides 10 G/s-class PONs with the two-dimensionally expanded dynamic range of 22.5 dB with very wide repeater-OLT link loss margin, both of which allow much greater flexibility in locating the repeater.

Colorless and plug-and-play technologies for WDM access over existing power-splitter-based infrastructure

Feature Issue on Passive Optical Network Architectures and TechnologiesWe present two key technologies, colorless and plug-and-play technologies, for WDM access that utilize the existing power-splitter-based infrastructure without change. For such power-splitter-based WDM access, optimum colorless approaches are discussed in comparison to the wavelength-splitter-based WDM access reported previously. We propose a remote wavelength setting procedure to achieve the plug-and-play function, which remotely and automatically sets up the initial wavelengths for each optical network unit. Issues facing power-splitter-based WDM access are clarified, and the feasibility of the plug-and-play function is shown over the power-splitter-based infrastructure.

A remote wavelength setting procedure based on wavelength sense random access (λ-RA) for power-splitter-based WDM-PON

We propose a remote wavelength setting procedure to achieve a colorless ONU for a WDM-PON that uses the existing power-splitter-based infrastructure. Issues for this power-splitter-based WDM-PON are clarified and the feasibility is demonstrated.

Field Trial of Long-Reach and High-Splitting λ-Tunable TWDM-PON

This paper presents the worlds 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.