Nguyen-Cac Tran

10-Gb/s transmission over 20-km single fiber link using 1-GHz RSOA by discrete multitone with multiple access.

We demonstrate a novel 10Gb/s 20km single fiber transmission link based on a remotely fed 1GHz-bandwidth-limited RSOA. Adaptive loading with discrete multitone was applied. We also report flexible-bandwidth-allocated multiple access based on the proposed idea.

The merits of reconfigurability in WDM-TDM optical in-building networks

Blocking performance of an optical WDM-TDM in-building network is significantly improved by dynamic wavelength routing. We analyse optimum clustering of users which reduces system complexity while largely preserving network performance improvement.

61.3-Gbps Hybrid Fiber-Wireless In-Home Network Enabled by Optical Heterodyne and Polarization Multiplexing

A hybrid fiber-wireless in-home network is proposed to support high-speed multiple input and multiple output (MIMO) orthogonal frequency division multiplexing systems operating at millimeter wave (mm-wave) band by employing optical heterodyne (OH) and polarization multiplexing (PolMux). OH enables the optical generation of mm-wave signals without the intrinsic frequency limitation of electrical local oscillators. Moreover, the frequency agility can be provided by tuning the optical wavelength in an OH system. PolMux explores two orthogonal polarizations at the same optical wavelength to satisfy the wireless MIMO service with low additional cost. Enabled by these techniques, the fiber transmission (1 km) and wireless delivery (1 m) of 61.3-Gbps data at 40-GHz mm-wave are successfully demonstrated. To the best of our knowledge, a record spectral efficiency of 6.82 bit/s/Hz is achieved in such kind of systems.

Cyclic-linked flexibility: An architectural approach for reconfigurable optical WDM-TDM access networks

Next-generation optical access networks should not only increase capacity but also be able to redistribute capacity on the fly in order to manage larger variations in traffic patterns. Wavelength reconfigurability is an instrument that can enable such capability of network-wide bandwidth redistribution since it allows dynamic sharing of both wavelengths and timeslots in WDM-TDM optical access networks. However, reconfigurability typically requires tunable lasers and tunable filters at the user side, resulting in cost-prohibitive optical network units (ONUs). In this paper, we propose a novel concept, named cyclic-linked flexibility, to address the cost-prohibitive problem. By using cyclic-linked flexibility, the ONU needs to switch only within a subset of two preplanned wavelengths, but the cyclic-linked structure of wavelengths allows free bandwidth to be shifted to any wavelength by a rearrangement process. A basic rearrangement algorithm is developed to demonstrate that cyclic-linked flexibility performs close to a fully flexible network in terms of blocking probability, packet delay, and packet loss. Furthermore, we show that the rearrangement process has minimum impact on in-service ONUs. To realize cyclic-linked flexibility, a physical implementation is proposed with a feasible cost and wavelength-agnostic ONU design.

Flexibility Level Adjustment in Reconfigurable WDM-TDM Optical Access Networks

Optical access networks have been widely adopted to support the exponential growth in bandwidth demand. To further fulfill the growth efficiently, reconfigurable wavelength division multiplexing–time division multiplexing optical access networks have been proposed in which optical network units can be reallocated to another wavelength on demand. Thus, the reconfigurability allows dynamic sharing of both wavelengths and timeslots. However, it requires a substantial addition to capital expenditure per user, which is prohibitive in access networks. This paper investigates an approach to preserve the merits of reconfigurability while significantly reducing the network complexity, thus cost by adjusting the level of flexibility. We define a parameter designated as the degree of flexibility to indicate the level of flexibility of a network. Then, we evaluate the performance of various degrees of flexibility based on the traffic capacity and the power consumption. The results suggest that introducing limited wavelength flexibility to the network significantly improves the performance in comparison to the static network while a highly or fully flexible network can further improve the performance but with smaller additional margins. Finally, we apply this result to a well-known reconfigurable architecture, the broadcast-and-select, to illustrate how the limited flexibility can help to reduce the network cost in terms of the optical power budget.

Dynamically Delivering Radio Signals by the Active Routing Optical Access Network

In this letter, we present a dynamic distributed antenna system based on a reconfigurable optical access network. Radio signals from the central office are delivered to the remote antenna units by means of optical channels where dynamic radio sub-carrier assignment to the antenna units is performed by reconfiguring optical channels. The bidirectional transmission experiment demonstrates that a switching time of 450 ns can be used to allocate an additional radio channel to antenna units. The impact to existing radio signals is negligible. The error vector magnitude penalty is only 0.5% and 1% for the downlink and uplink radio signals, respectively.

Demonstration of Long-Reach PON Using 10 Gb/s 3R Burst-Mode Wavelength Converter

Long-reach optical access networks promise significant cost savings. To merge existing metro and access networks to a single long-reach network, the long-reach technology has to address not only the power loss and fiber dispersion problems but also mismatch between two merged entities in terms of wavelengths and operational modes, especially during the transition period when support of legacy services is still required. In this letter, we demonstrate a long reach network employing a 10 Gb/s burst-mode O/E/O wavelength converter. The converter can simultaneously address the power loss, dispersion, and mismatch problems by a compact assembly. Two upstream wavelengths located in the 1310 nm and 1550 nm windows in the access section are converted to a DWDM wavelength of 1554.13 nm in the metro section. Error-free performance is achieved with a loud/soft ratio of 10 dB at a sensitivity of -27 dBm and the overhead for the burst-mode operation is as low as 0.512%.

Recent research advancements in in-building optical networks

For in-building communication, a powerful backbone network can be created by means of optical fibre, which in a single infrastructure can offer a wealth of both fixed and wireless service connections to the users. Next to the technological challenges, important aspects to be taken into account are the economics of network installation and operation, and sustainability. An overview is given of recent research results regarding the optimization of network architectures, and regarding advanced signal processing for economical and sustainable delivery of high-capacity wired and wireless services over various types of multimode (plastic) optical fibre.

Utilizing unused power budget to increase network capacity in practical PON deployments by introducing flexible modulation

The actual use of power budgets in a PON typically varies widely. Utilizing 4-PAM modulation for ONUs that have high power margins can increase network capacity utilization without investing in expensive optics. We demonstrate that the capacity can increase 79%.