Pandelis Kourtessis

Toward terabit-per-second capacities over multimode fiber links using SCM/WDM techniques

This paper outlines the progress made on the use of subcarrier multiplexing (SCM) for high-speed datacommunications links over multimode fiber. Results include the demonstration of penalty-free transmission of 2.5 Gb/s data over worst case multimode fiber (MMF). A complete link demonstration of an SCM transmission system is reported, based on a quadrature phase-shift keying modulator and demodulator capable of a record 5.1 Gb/s per subcarrier data transmission. Superior performance compared with conventional baseband modulation techniques is shown. It is also demonstrated that when SCM is combined with dense wavelength-division multiplexing (WDM), aggregate data capacity of 200 Gb/s is feasible. Preliminary results demonstrate the possibility of 20-GHz WDM channel spacings, which if scaled show the potential for 1-Tb/s aggregate rates with a bandwidth-length product of 3 Tb/s/spl middot/km.

An OFDMA-based optical access network architecture exhibiting ultra-high capacity and wireline-wireless convergence

This article presents ACCORDANCE, a novel optical access network architecture based on OFDMA technology and applied on a PON topology. In compliance with next generation optical access requirements, this architecture aims to outperform existing PON solutions in terms of total capacity, bandwidth allocation flexibility, number of users, and network reach. Moreover, it provides the opportunity for convergence with wireless technologies and a smooth migration path from legacy access solutions like TDMA-PONs and DSL.

Full-Service MAC Protocol for Metro-Reach GPONs

An advanced medium access control protocol is presented demonstrating dynamic bandwidth allocation for long-reach gigabit-capable passive optical networks (GPONs). The protocol enables the optical line terminal to overlap the idle time slots in each packet transmission cycle with a virtual polling cycle to increase the effective transmission bandwidth. Contrasting the new scheme with developed algorithms, network modeling has exhibited significant improvement in channel throughput, mean packet delay, and packet loss rate in the presence of class-of-service and service-level differentiation. In particular, the displayed 34% increase in the overall channel throughput and 30 times reduction in mean packet delay for service-level 1 and service-level 2 optical network units (ONUs) at accustomed 50% ONU load constitutes the highest extended-reach GPON performance reported up to date.

ACCORDANCE: A novel OFDMA-PON paradigm for ultra-high capacity converged wireline-wireless access networks

This paper presents ACCORDANCE, a novel ultra-high capacity extended reach optical access network architecture based on OFDMA technology/protocols, implemented through the proper mix of state-of-the-art photonics and electronics. Such architecture is not only intended to offer improved performance compared to evolving TDMA-PON solutions but also provide the opportunity for convergence between optical, radio and copper-based access. Although OFDM has been used in radio and copper-based communications, it is only recently that is making its way into optics and is expected to increase the system reach and transmission rates without increasing the required cost/complexity of optoelectronic components. ACCORDANCE hence aims to realize the concept of introducing OFDMA-based technology and protocols (Physical and MAC layer) to provide a variety of desirable characteristics, such as increased aggregate bandwidth and scalability, enhanced resource allocation flexibility, longer reach, lower equipment cost/complexity and lower power consumption, while also supporting multi-wavelength operation. In addition, it enables the convergence of the optical infrastructure with standard wireless solutions, thus offering a way to integrate dominant wired and wireless technologies in a hybrid access network supporting seamless ubiquitous broadband services.

Demonstration of Wireless Backhauling Over Long-Reach PONs

An IEEE 802.16e-2005 (WiMAX) compliant, long- reach passive optical network is demonstrated, focusing on the development of next generation optical access with transparent wireless backhauling. In addition to the extended feeder reach, a wavelength band overlay is used to enhance network scalability by maintaining passive splitting in the field and with some design modification at the optical line terminal and remote base station. Radio-over-fiber is used to minimize network installation and maintenance costs through the use of simple remote radio heads complemented by frequency division multiplexing to address individual base stations. The implementation of overlapping radio cells/sectors is also proposed to provide joint signal processing at wireless user terminals. Experimental measurements confirmed EVMs below -30 and -23 dB downstream and upstream, respectively, over fiber link lengths of up to 84.6 km. In addition, adjacent channel leakage ratio measurements demonstrated that a figure of -45 dB with 40 MHz subcarrier spacing, as specified by the standard, can be readily achieved.

Dynamic Subcarrier Allocation for 100 Gbps, 40 km OFDMA-PONs With SLA and CoS

The quality of service of 100 Gbps orthogonal frequency division multiple access passive optical networks (OFDMA-PONs) performing dynamic bandwidth allocation is evaluated. New medium access control protocols and frame formats have been developed, exhibiting hybrid OFDMA/time division multiple access scheduling, for capacity enhancement and granular bandwidth allocation. The sequential dynamic subcarrier allocation algorithms allow the network optical line terminal to grant the optical network units (ONUs) bandwidth using both status and non-status based algorithm. Simulations of a 100 Gbps network with 256 ONUs, 256 subcarriers and 40 km extended-reach demonstrate best network throughputs of 87.5 Gbps and 3 ms packet delays for high priority service classes, even at maximum ONU load. In addition, high service level agreement (SLA) ONUs exhibit 1.56 Gbps maximum capacity and 48.82 kbps granularity.

Colorless FDMA-PON with flexible bandwidth allocation and colorless, low-speed ONUs [invited]

We demonstrate a remotely seeded flexible passive optical network (PON) with multiple low-speed subscribers but only a single optical line terminal transceiver operating at a data rate of 31.25 Gbits/s. The scheme is based on a colorless frequency division multiplexing (FDM)-PON with centralized wavelength control. Multiplexing and demultiplexing in the optical network unit (ONU) is performed in the electronic domain and relies either on FDM with Nyquist sinc-pulse shaping or on orthogonal frequency division multiplexing (OFDM). This way the ONU can perform processing at low speed in the baseband. Further, the ONU is colorless by means of a remote seed for upstream transmission and a remote local oscillator for heterodyne reception, all of which helps in keeping maintenance and costs for an ONU potentially low and will simplify wavelength allocation in a future software defined network architecture. To extend the reach, semiconductor optical amplifiers are used for optical amplification in the downstream and upstream.

Multi-PON access network using a coarse AWG for smooth migration from TDM to WDM PON

An interoperable access network architecture based on a coarse array waveguide grating (AWG) is described, displaying dynamic wavelength assignment to manage the network load across multiple PONs. The multi-PON architecture utilizes coarse Gaussian channels of an AWG to facilitate scalability and smooth migration path between TDM and WDM PONs. Network simulations of a cross-operational protocol platform confirmed successful routing of individual PON clusters through 7 nm-wide passband windows of the AWG. Furthermore, polarization-dependent wavelength shift and phase errors of the device proved not to impose restrain on the routing performance. Optical transmission tests at 2.5 Gbit/s for distances up to 20 km are demonstrated.

Advanced PON topologies with wireless connectivity

The interoperability of wireless and PON networking solutions is investigated to reduce deployment expenditure by means of centralised network management while providing ubiquitous access connections and mobility. Network modelling in the physical layer of WiMAX channel transmission based on FDM over legacy PONs has demonstrated EVMs below −30 dB and error-free multipath transmission. In addition, the development of a dynamic MAC protocol suite has been presented to assign bandwidth between the OLT and ONU BaseStations over a multi-wavelength, splitter-PON topology to demonstrate converged network scalability. This has been achieved by managing data-centric traffic with quality of service in view of diverse multi-user access technologies.

Interoperability of GPON and WiMAX for network capacity enhancement and resilience

The interoperability of standard WiMAX and gigabit passive optical networks (GPONs) is shown to overcome the wireless spectrum congestion and provide resilience for GPON through the use of overlapping radio cells. The application of centralized control in the optical line terminal and time division multiplexing for upstream transmission enables efficient dynamic bandwidth allocation for wireless users on a single wavelength as well as minimized optical beat interference at the optical receiver. The viability of bidirectional transmission of multiple uncoded IEEE 802.16d channels by means of a single radio-frequency subcarrier at transmission rates of 50 and 15 Mbits/s downstream and upstream, respectively, for distances of up to 21 km of integrated GPON and WiMAX microcell links is demonstrated.