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Final Report Summary - QUATERNIAN (Quantum Dot Technologies for Extended Reach Nodes In Access Networks)

Executive Summary:
The QUATERNIAN project brought the technology of quantum-dot active materials to three SME companies searching for new products and processes to safeguard their future commercial activities.
Quantum-dot technology is semiconductor wafer based process such as is currently the standard for semiconductor laser production. The advance provided by these materials is that their nanostructuring is able to tune the properties of the laser. These quantum-dots do not pose a health hazard beyond those of any other semiconductor light source, as the quantum dots are grown into a crystal matrix.
The project was highly successful in providing and controlling high power Raman pump modules for extending the reach of optical access networks, to provide large cost savings; the project delivered advanced packaging solutions to its SMEPs, allowing them to access high speed laser markets; the project uncovered new approaches to the interface of radio-frequency ID technology with an optical layer.
The SME partners are currently exploring both the near-term and long-term commercial opportunities opened by the project.

Project Context and Objectives:
The goal of the QUATERNIAN project is to move the technology of quantum-dot semiconductor lasers from its research setting, and into the product ranges of a set of high-technology SMEs, concerned with expanding the reach of high-speed internet.
Quantum-dot growth is a recent technological development made possible by conceptual and engineering advances in the theory and growth of semiconductor materials. In this growth mode, the typical planar growth of semiconductor layers is deliberately disrupted so the critical active region forms nanometre scale droplets within the crystal matrix. This nanostructure acts to control the momentum, and thus the energy of charge carriers in the semiconductor. This additional control mechanism has been recognised as having excellent potential to improve laser performance, such as improved temperature performance, better resistance of optical reflections, and high power from low cost substrates. This promise has seen strong funding agency support for research in this area, from both European and national sources, that has led to large advances in capability. In this project, we will transfer such know-how to a group of innovative European companies seeking technological advantage in the marketplace.
The three SMEs at the focus of QUATERNIAN are working to expand their markets in the space of optically supported access networks. Their segments of these markets differ, and the SME partners interests are thus complementary. Eblana Photonics wishes to expand its line of transmitter lasers for passive optical networks (PON), in particular to obtain high speed packaging and laser driving technology. BDI operates in the market of advanced building services, including communications architecture. To this end they desire to bring to market a set of highly developed distributed Raman amplifiers. This has required not only the development of high efficiency, high power quantum-dot lasers, but also the amplifier controls capable of coping with burst mode data transfer, and the associated transients. Finally, PervasID innovates in the space of radio-frequency short-range communication. The advanced antenna technology of QUATERNIAN will allow them to deliver pervasive radio coverage even in buildings of high density.
The technological objectives of QUATERNIAN can be summarised as

1.Greater than 15 dB of Raman gain in standard fibre at the upstream wavelength of 1270 nm.
2.QD-laser relative intensity noise (RIN) of <-150 dB/Hz, with high linearity

3.Extended reach (ER) PON at 10 Gb/s supported by distributed Raman amplification
5.LTE and WiMAX standards implemented on multiple-input multiple-output (MIMO) network. By achieving these goals, the project will equip the SME partners with valuable technical expertise and help them achieve their growth objectives.

Project Results:
The work of the project can be divided into four sections: quantum dot laser development for with high speed signal and high power use; the development of microwave packaging and modulation solutions; optical systems testing and development; and distributed antenna systems.
In Distributed Antenna Systems, it has been shown that the proposed MIMO-enabled ROF system using phase quadrature DSB frequency translation technique is a low-cost solution for wide-band (LTE/Wi-Fi), multiple- service DAS system. Both the EVM and condition number of the system is shown to be low (within the standard requirement), and the calculated system capacity can be >90 bis/s/Hz. In addition, it has been experimentally shown that in the 3×3 case, the MIMO DAS system can provide better condition number and capacity performance, compared with a CAS system, no matter when replication number is 1 or 3, in LOS or NLOS circumstance.
In microwave packaging and modulation solutions, a 10 Gb/s laser package has been designed, fabricated and tested, and the package has shown high performance at 10 Gb/s digital laser modulation. A burst mode laser driver chip set design has been demonstrated, and supplied to Eblana Photonics showing clean 10 Gb/s eye, in both continuous modulation and burst mode modulation mode.
In quantum dot laser development, the outcomes have been partially successful. The high power Raman pump lasers have performed excellently, exhibiting peak Raman gains of 18 dB for a single pump pair, despite operating below the fibre cutoff wavelength. A design based on these experimental results has also been developed that can provide flat gain across the entire X-GPON band with only two pump wavelengths. The high speed signal lasers have achieved high power output and high spectral purity, but have not achieved sufficient modulation bandwidth or temperature performance. It has been shown that the optical loss introduced by the slot process cannot be overcome by the limited gain of the quantum dot material. This leads to high relaxation oscillation damping (reducing the bandwidth) and a tendency to lase in the Excited State, rather than the Ground State when either high bias is applied or the temperature is high.
In optical systems, the initial plan to use traditional on-off keying of the transmission laser was limited to 2.5 Gb/s due to the limited modulation bandwidth. To achieve 10 Gb/s, a novel Optical-OFDM technique has been developed and demonstrated over a Raman amplified 40 km link.

Potential Impact:
The potential impact of the QUATERNIAN project is based on the needs of its SME partners to improve their technological capabilities. This will be reflected in additions to their product lines, and increased visibility of the SME partners in the space of high technology. These advance in their position has the potential to impact upon society in a number of ways:
* New products will lead directly to new employment in the European high technology design area, an area crucial to be retained with the EU
* Publicity as technology innovators will draw customers to work with the SME partners both to create new products, and to use their existing portfolio of products. This will increase the impact of previous funding support, and lead to new solution creation
* Several of the new technologies developed project have the potential to reduce costs to levels where they may be deployed. This economic advantage will lead to the roll-out of technologies that would otherwise have been trapped at the design stage and therefore an improvement in the quality of services offered to citizens
* A number of the foreground results delivered will be primarily commercial in utility, but the proposed optical extension to radio-frequency ID technology could be directly experienced by the public in improved security for their goods and persons.

The QUATERNIAN project is advanced technologically, and thus the major dissemination channels have been addressed towards technical audiences from industry and academia. The consortium have reached out to this audience through numerous presentations at technical events such as: Viktorov et al., “Optothermal excitabilities and instabilities in quantum dot lasers”, Photonics West, San Jose 2015; Tykalewicz et al., “Ultrafast dynamic switching between two lasing states in quantum dot lasers”, Photonics West, San Jose 2015; Tykalewicz et al., “All-optical switching with a dual state quantum dot laser”, SPIE Photonics Europe, Brussels 2014; Kelleher et al., “Feedback generated periodic pulse trains in quantum dot lasers“ SPIE Photonics Europe, Brussels 2014; Antony et al., "XG-PON Raman Reach Extender Based on Quantum Dot Lasers", European Conference and Exhibition on Optical Communication (ECOC), Cannes 2014. These conference presentations largely have been or will be followed by peer-reviewed journal publications to provide a permanent record of the research results.

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