This PDF file contains the front matter associated with SPIE Proceedings Volume 7234, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

This paper describes convergence of optical and wireless access networks for delivering high-bandwidth integrated services over optical fiber and air links. Several key system technologies are proposed and experimentally demonstrated. We report here, for the first ever, a campus-wide field trial demonstration of radio-over-fiber (RoF) system transmitting uncompressed standard-definition (SD) high-definition (HD) real-time video contents, carried by 2.4-GHz radio and 60- GHz millimeter-wave signals, respectively, over 2.5-km standard single mode fiber (SMF-28) through the campus fiber network at Georgia Institute of Technology (GT). In addition, subsystem technologies of Base Station and wireless tranceivers operated at 60 GHz for real-time video distribution have been developed and tested.

Achieving an all-optical connection between any wireless communication systems with optical fiber network is one of the ultimate goals of communication network design. An all-optical system providing seamless connection between freespace and optical fiber links by using free-space optical (FSO) communication technology suitable for next generation network has been developed. In order to realize this next-generation FSO communication system in which the transmitted light signal does not undergo any conversion thus achieving all-optical connection, it is necessary to develop a technology for tracking and focusing the free-space optical signal to a single mode fiber (SMF). The developed FSO system incorporates a fine pointing mirror (FPM) for high speed beam control and steering. This novel tracking method can suppress the beam intensity variations as a result of angle-of-arrival fluctuation (AOA) caused by atmospheric turbulence. This paper presents experimental results of a next-generation FSO system providing stable and reliable single channel transmission at 10 Gbps data rates as well as multiple channels using dense wavelength division multiplexing (DWDM). This kind of data rate is not possible to achieve using conventional FSO systems. The developed system can provide transmission capacity equivalent to optical fiber and from its design concept and configuration it is bit-rate and protocol transparent. Furthermore, we present research on Radio-on-FSO (RoFSO) system which is a combination of the developed nextgeneration FSO system and Radio over Fiber (RoF) technology. We demonstrate the possibility of utilizing this system for optical and radio frequency signals transmission. RoFSO technology is independent of the difference in the underlying physical layers for radio system or fiber system, but realizing fusion at the service level. The RoFSO technology is available to realize a universal platform for transparent forwarding various wireless services in a ubiquitous network environment.

In wireless mesh networks using unlicensed radio frequency band, how to adaptively and efficiently allocate spectrum among multiple wireless nodes according to the surrounding environment is an important issue. Cognitive radio that includes functionalities of radio environmental awareness and intelligent radio resource management in an opportunistic way is regarded as the great candidate to enable the efficient utilization of radio resource. In order to fully exploit radio resources and enhance spectrum efficiency based on cognitive radio to wireless mesh networks, this paper proposes dynamic subcarrier selection technique and CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) based MAC layer protocol for wireless mesh networks. In the proposed technique, based on the detection of available spot-wise subcarriers using the subcarrier-level carrier sense and the estimation of channel conditions, data packet is transmitted using unused discrete subcarriers having good channel conditions. Numerical results confirm that the proposed dynamic subcarrier selection technique is effective in utilizing radio resources and enhance spectrum efficiency. Moreover, because multiple nodes can get the transmission opportunity at the same time, the degradation in transmission performance due to the contention between multiple nodes can be solved.

Technologies for the transport of radio over optical fiber links have been developing rapidly in recent years and bandwidth demands have spurred researchers to look into higher frequencies and smaller cell sizes. Although many of the underlying techniques are developed, significant challenges still remain before these technologies can be integrated in fully functioning networks. This talk will review the recent developments in Radio-Over-Technologies, highlight the challenges that remain and outline the work being undertaken within the EU Network of Excellence BONE to meet these challenges.

We will introduce four related topics about fiber access network technologies for PONs. First, an upstream signal powerequalizer is proposed and designed using a FP-LD in optical line terminal applied to the TDM-PON, and a 20dB dynamic upstream power range from -5 to -25dBm having a 1.7dB maximal power variation is retrieved. The fiber-fault protection is also an important issue for PON. We investigate a simple and cost-effective TDM/WDM PON system with self-protected function. Next, using RSOA-based colorless WDM-PON is also demonstrated. We propose a costeffective CW light source into RSOA for 2.5Gb/s upstream in WDM-PON together with self-healing mechanism against fiber fault. Finally, we investigate a 4Gb/s OFDM-QAM for both upstream and downstream traffic in long-reach WDM/TDM PON system under 100km transmission without dispersion compensation. As a result, we believe that these key access technologies are emerging and useful for the next generation broadband FTTH networks.

Due to reduced operational and equipment costs, time division multiplexed (TDM)-based passive Optical Network (PON) access solutions including Gigabit PON (GPON) and Ethernet PON (EPON) have been widely accepted as a viable technology for the implementation of fiber-to-the-x (FTTx) solutions, and are being deployed globally. Users are increasingly requiring more bandwidth for high end applications and at the same time greater mobility. The convergence of fiber and wireless systems is seen as the optimum solution to offer the combination of the fiber capacity and the wireless mobility. PON has been proposed as a backhaul for wireless. Typical architectures are traditionally deployed as tree topologies. However, tree-based topologies have several inherent drawbacks such as inability to support a truly shared Local Area Network (LAN) capability among end users. In this paper, we propose scalable ring-based architectures that offer truly shared LAN capability as well as dynamic bandwidth allocation. These architectures are ring-based as well as hybrid, combination of tree-based and ring-based. These flexible architectures can be used as the back-haul to wireless by incorporating the base stations in the ONU locations. Our proposed hybrid PON ring architecture is scalable to 78 ONUs without the use of any amplifiers and in addition, the basic ring architecture and in turn the hybrid one is transparent to protocols and data rates and hence allows for greater BW flexibility as well as greater number of serviced end-users.

A new bidirectional wavelength division multiplexing - radio over fiber scheme is proposed with multi optical carrier suppression for simultaneous wired and wireless 1.25-Gbps signal transmission. For downstream signals, all modes of a Fabry Perot laser diode are simultaneously suppressed by a Mach-Zehnder modulator at V_π bias point to mitigate a chromatic dispersion. A reflective SOA is used both for reduction of mode partition noise induced from the Fabry Perot laser diode and for the downstream modulation of each channel. The effect of MPN reduction is verified by measuring RF spectra and phase noises. For an upstream signal, another reflective SOA in BS is used by re-modulation technique, which is verified by measuring both the RF spectra and a dynamic rage of an optical input power to the RSOA. A BER of 10^-11 for three downlink channels and one uplink channel at 1.25-Gbps are experimentally demonstrated after 23-km SMF transmission.

This paper reviews recent development in bend-insensitive fibers for fiber-to-the-home (FTTH) applications. First, requirements for bend-insensitive fibers are discussed. Then different design approaches for reducing fiber bending loss are described and compared. A new bend-insensitive fiber using the nano-engineered ring design is presented in detail.

Polymer Optical Fibres (POFs) show clear advantages compared to copper and glass fibres. In essence, POFs are inexpensive, space-saving and not susceptible to electromagnetic interference. Thus, the usage of POFs have become a reasonable alternative in short distance data communication. Today, POFs are applied in a wide number of applications due to these specific advantages. These applications include automotive communication systems and in-house-networks. State-of-the-art is to transmit data with only one channel over POF, this limits the bandwidth. To solve this problem, an integrated MUX/DEMUX-element for WDM over POF is designed and developed to use multiple channels. This integration leads to low costs, therefore this component is suitable for mass market applications. The fundamental idea is to separate the chromatic parts of the light in its monochromatic components by means of a grating based on an aspheric mirror. Due to the high NA of the POF the setup has to be designed in a 3D-approach. Therefore this setup cannot be compared with the planar solutions available on market, they would result high losses in the 3rd dimension. To achieve a fast and optimized design an optical simulation program is used. Particular attention has to be paid to the design of the POF as a light source in the simulation program and the optimisation of the grating. The following realization of the demultiplexer is planed to be done with injection molding. This technology offers easy and very economical processing. These advantages make this technology first choice for optical components in the low-cost array.

This paper describes recent progress of high-speed vector optical modulation technologies based on Mach- Zehnder interferometer devices. Multi-level quadrature amplitude modulation signal can be synthesized by using parallel Mach-Zehnder modulators. We can generate complicated multi-level optical signals from binary data streams, where binary modulated signals are vectorially summed in optical circuits. Modulation speed can be higher than 80 Gbaud by using a dual parallel Mach-Zehnder modulator with thin lithium niobate substrate.

Ultra-linear modulators are critical components for broadband access applications in analog fiber-optic communication links, such as Radio-over-Fiber (RoF), Radio-over-Free Space (RoFS) and ultra-dense (cable television) CATV. In our previous work, it was shown that an ultra-linear optical modulator - composed of a phase modulator and ring resonator in a Mach-Zehnder (MZ) configuration, exhibited SFDR values > 130 dB. In this paper, we introduce a new configuration based on a lumped electrode design, in which the phase modulator (PM) is on one arm of the MZ and the ring resonator (RR) is located on the other arm. We also carefully control and monitor the power split ratio of an RF input to both the PM and the RR, in addition to the RF phase bias between the RR and PM. We report its unique and superior features such as superior linearity (SFDR ~ 133 dB), modulation bandwidth extension (as much as 70%) over the ring resonator-assisted Mach Zehnder design and high link gain. Lastly, we discuss the merits of the design flexibility, practicality and ease of use of the new modulator.

We propose and demonstrate a pre-distortion method for reducing the third-order intermodulation distortion (IMD3) of the distributed-feedback laser diode. The pre-distortion scheme consists of two loops and uses two laser diodes (LD), a photodetector (PD), RF attenuators, RF combiners/dividers, and an RF amplifier. In our scheme, the error signal is generated by the slave LD through controlling the phase and attenuation adjustment in the inner loop and then drives the master LD to reduce nonlinear property in the outer loop. The experimental results show that the significant reduction of about 30 dB in the third-order intermodulation distortion (IMD3) is achieved at 2.4 GHz in the implemented system. For the broad frequency range from 1.97 GHz to 2.48 GHz (510 MHz), IMD3 is enhanced by more than 10 dB.

An injection-seeding bandwidth of 4 THz (1042-1057 nm) was successfully obtained for a quantum-dot (QD) Fabry- Perot laser diode operating in a 1-μm optical waveband. The operation of a fabricated laser was investigated for transmission through a 1-km hole-assisted fiber (HAF), and clear eye-openings and almost power-penalty-free transmission were successfully demonstrated with respect to 2.5 Gbps for various wavelengths in the 1-μm band.

A scheme for high speed clock and data recovery using an electroabsorption modulated laser and a semiconductor optical amplifiers arranged in an optical-electrical-optical (OEO) loop has been demonstrated. By injecting the 80Gb/s optical data into the OEO ring, the 10GHz clock tone is traced and amplified in the loop. A 10GHz electrical clock and, a 10 GHz optical clock are recovered simultaneously.

Development of fiber optic communications networks has continued in virtually all geographies of the world. Some calculate that expansion in the USA alone will continue to 2025. After that time there will maintenance, upgrade, and replacement. While some nations are more advanced than others and some enterprises more sophisticated than others, the undeniable reality is that previous networks will, in some fashion or another, include fiber optics. The future need is for speed and reliable bandwidth: lots of it. Decisions will be made based on new concepts that will enable far more data at far faster rates than once considered feasible or necessary. As the consumer enters the market with newly engineered home entertainment systems, additional burdens will be placed on both OEM and OSP. These are not negative challenges, but rather indicators of a new generation of consumers with awareness and demand far more advanced any may have imagined just a few years ago.

A new architecture for bidirectional millimeter-wave band radio-over-fiber system is proposed; both optical carrier suppression and injection locking effect are used to simultaneously generate a 1.25-Gb/s wired signal and a 63-GHz wireless one. Error free transmissions (bit error rate of 10^-11) of downlink and uplink data are achieved to verify the proposed scheme. No impact of a downlink data transmission on an uplink one due to the wavelength reuse is observed. It is checked that there is only the 2-dB power penalty of uplink due to the Rayleigh backscattering noise.

This paper firstly derives a new model of RoFSO (Radio on Free Space Optics) channel considering fluctuation speed of the scintillation and the probability density function (p.d.f) of the random and time-correlated optical intensity disturbed by scintillation. The relationships among frequency characteristic of RoFSO channel, variance of received optical intensity and atmospheric conditions (temperature and insolation) are statistically analyzed by the proposed model. By using the proposed model and the relationships, the throughput performance of WLAN (802.11a) over RoFSO link is evaluated with computer simulations. For two cases of without-shadowing and with-shadowing in the radio propagation channel, evaluations of degradation due to scintillation are conducted. As a result, it is found that the degradation due to scintillation is much smaller than that due to shadowing in the throughput performance for WLAN.

A visible-light communication utilizing LED has many advantagies such as visibility of information, high SNR (Signal to Noise Ratio), low installation cost, usage of existing illuminators, and high security. Furthermore, exponentially increasing needs and quality of LED have helped the development of visible-light communication. The visibility is the most attractive property in visible-light communication system, but it is difficult to ensure visibility and transmission efficiency simultaneously during initial access because of the small amount of initial access process signals. In this paper, we propose an efficient resource allocation scheme at initial access for ensuring visibility with high resource utilization rate and low data transmission failure rate. The performance has been evaluated through the numerical analysis and simulation results.