A novel long-reach passive optical network (PON) architecture based on hybrid dense wavelength-division multiplexing (DWDM) and time-division multiplexing (TDM) is presented as a possible candidate for the next generation of optical access networks. The approach combines access and backhaul functions in a single optical network infrastructure that links end customers directly to core networks without the need for intermediate electronic conversions. A centralized optical carrier distribution and wavelength-independent remote modulation scheme is employed to avoid the potential inventory and deployment costs associated with the use of wavelength-specific lasers in the customer transmitter (TX). The customer TX is based on an electroabsorption modulator (EAM) monolithically integrated with two semiconductor optical amplifiers (SOAs), providing sufficient net gain and bandwidth to support large splitting factors and upstream bit rates up to 10 Gb/s. The experimental results reported show that the network, with a total reach of 100 km and an upstream bit rate of 10 Gb/s, can potentially support 17 TDM PONs operating at different wavelengths each with up to 256 customers, giving an aggregate number of 4352 customers in total.

Hybrid DWDM-TDM long-reach PON for next-generation optical access

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.

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

There has been an increasing interest in photonic generation of RF signals in the millimeter-wave (30 GHz ∼ 300 GHz) and/or terahertz-wave (0.1 THz ∼ 10 THz) regions, and photodiodes play a key role in it. This paper reviews re- cent progress in the high-power RF photodiodes such as Uni- Traveling-Carrier-Photodiodes (UTC-PDs), which operate at these frequencies. Several approaches to increasing both the bandwidth and output power of photodiodes are discussed, and promising applications to broadband wireless communications and spectroscopic sensing are described. Photodiode chip is bonded to the substrate with the antenna. This is a symbolic figure of RF photonics in this article. Antenna

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High-power RF photodiodes and their applications

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.

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

An efficient gain-flattened L-band optical amplifier is demonstrated using a hybrid configuration with a distributed Raman amplifier (DRA) and an erbium-doped fiber amplifier (EDFA) for 160 × 10-Gb/s dense wavelength division multiplexed system at 25-GHz interval. With an input signal power of 3 mW, a flat gain of >; 10 dB is obtained across the frequency range from 187 to 190.975 THz with a gain variation of ; 8.9 dBm) ever reported for a DRA-EDFA hybrid optical amplifier at reduced channel spacing.

Flat-Gain L-Band Raman-EDFA Hybrid Optical Amplifier for Dense Wavelength Division Multiplexed System

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.

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

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.

Access and metro networks based on WDM technologies

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.

Application of super-DWDM technologies to terrestrial terabit transmission systems

This paper reports the world's 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.

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

A novel photonic millimetre-wave (MMW) generator that uses an intensity modulator and a phase modulator is presented. A 125 GHz MMW signal is generated and its feasibility for 10 Gbit/s wireless links is confirmed.

Fujiwara Masamitsu

Papers

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

Access and metro networks based on WDM technologies

Application of super-DWDM technologies to terrestrial terabit transmission systems

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

Photonic millimetre-wave generator using intensity and phase modulators for 10 Gbit/s wireless link