Technology

UROOF versus Radio-over-Fibre (RoF)

Ultra-wideband radio over fiber (UROOF) is a novel technology in the field of short-range communication applications. The main goal is to enable range extension of 1 to 3 orders of magnitude over a typical UWB radio signal in the range of 3.1-10.6 GHz. Similar to RoF, UROOF's technology allows separation of low cost Base-Station (BS)s from the Central-Station (CS). The main differences between UROOF and the conventional RoF are:

Innovative photonic components

UROOF project is aimed at studying and developing crucial innovative enabling technologies and photonic building blocks for broadband wireless/wired access based on UWB radio over optical fiber. These building blocks are based on novel low cost conversion methods and components from optical to UWB domain (i.e. O/UWB converter) and from UWB to optical (i.e. O/UWB converter). The overall objective is to provide a proof of concept for a new integrated access node consists of UWB access point combined with O/UWB and UWB/O photonic converters that enable range extension of 1 to 3 orders of magnitude over a typical UWB radio signal in the range of 3.1-10.6 GHz. UROOF technologies will be a key for implementing next generation short-range communication systems as part of the wireless world vision beyond 2010. More specifically, the project has the following objectives.

UROOF scientific objectives:

1. To investigate, develop, test and implement new device concepts for O/UWB conversion devices including:
  1. Concepts for converting devices based on photoconductivity effect in the microstrip line substrate and surface and topologies with vertical “photo induced load”.
  2. Approaches for O/UWB devices with photo-diode lateral and vertical load.
  3. Multi-line configuration to support multiband UWB transmissions in which each microstrip line conducting a carrier wave with a different frequency.
  4. Approaches that enable new bands for UWB radio technology based on microwaves- photonics mixing.
2. To investigate, develop, test and implement low-cost technologies for UWB/O conversion devices and integration with crucial UWB radio - microwaves components including:
  1. Utilizing direct modulation of laser diodes and vertical cavity surface emitting laser (VCSEL) for various UWB signals in the range 3.1-10.6 GHz.
  2. Enhanced electroabsorption modulators to UWB applications.
  3. Using the Mach-Zehnder modulator to UWB signals.

UROOF technological objectives:

3. To study and develop prototype for photonic components consisting of:
  1. Optically controlled microwaves converter (OCMC) with the following size: width 1cm, length 1-5cm height 0.5-1 mm capable of efficiently converting UWB modulated RF signal in a given band of 3.1 – 10.6 GHZ over fiber directly to UWB RF signal at the same original frequency band. Operational target wavelength: 850nm and 1350 nm.
  2. Photonic mixer based on OCMC with additional microwaves source, allowing conversion as in 3.a and additionally changing the band of the UWB signal.
  3. Modulator for UROOF signal based on VCSEL technology.
  4. Enhanced EAT for UROOF signals.
  5. Integrated UROOF Transceiver based on components 3.a ,3.c, or possibly 3.b , 3.c.
  6. Hybrid Integrated and low-cost UROOF Access Node comprising components 3d or 3e with RF front-end of UWB transceiver. Size: 10x5x0.5 mm3; Data rates: 100-480Mbps and Power level compliant with UWB mask. The target cost of the UROOF access node for low-cost applications (cases #1,2) is below 100€.

UROOF application objectives:

4. Detailed performance analysis of typical UROOF applications with different UWB modulation schemes to select the best technique for UWB radio over optical fiber (UROOF) distribution.

5. Provide a platform that includes the basic O/UWB and UWB/O converters and UWB blocks that will be serve as our proof of concept for key UROOF scenarios e.g., 1000 meters range extended UWB system; very low-cost distributed antenna system (VL-DAS); Security and homeland applications. These cases will be analysed and selected scenario will be in a system validation and be compared to theoretical analysis.

Innovative O/UWB technologies)

Optically controlled microstrip converter (OCMC)

Recently, the innovative field of MW-photonics has emerged. The state of the art in this technology consists of direct optical control of MW devices by creating a photo-generated electron-hole plasma in a high-resistivity semiconductor substrate. In UROOF it is developed the additional capability of direct conversion from UWB signal in the optical domain to the RF domain.

Photonic mixing of UWB signals

Another novel photonic component based on the same physical principles is a photonic mixing device which allows for mixing the UWB signal carried by the optical signal with an unmodulated microwave carrier. For this purpose, an external MW source, e.g. a local oscillator, is fed into the microstrip from its non-illuminated port. This results in a shift of the centre frequency of the UWB signal to higher frequencies in the 3.1-10.6 GHz band. This technique is expected to permit a highly efficient mixing when the external microwave frequency coincides with the resonant frequency of the illuminated microstrip line.

Enhanced EAT (T3.2, T3.9)

Within UROOF is is developed a novel EAT optimised for UWB operation. The EAM, is based on a buried quantum well structure hetero-structure will broad bandwidth and high optical power handling. This improved optical to RF and RF to optical conversion will be achieved using techniques such as electrically resonant drive-lines.

Low cost VCSEL

In UROOF project it is proposed low-cost direct modulated vertical cavity surface emission lasers (VCSEL's) for RF to optical conversion. VCSEL seems to be the most promising candidate for low-cost RoF systems due to their efficient coupling with optical fiber and the small number of longitudinal modes.

Circle 2: UROOF innovative devices

In order to realize the UROOF application scenarios, two novel devices will be developed that will be based on the UROOF photonic components. The devises will serve as bi-directional interfaces between the optical and RF domains.

Integrated UROOF Transceiver

It is a single device, which provides bi-directional conversion for O/UWB and UWB/O. This device is implemented by two different technologies: Figure 1 Figure 3: UWB/O - O/UWB transceiver

Hybrid board for the UROOF transceiver

This board is based on the hybrid technology for assembly and packaging of the photonic converters with the UWB front end. The hybrid technology provides the possibility of combining lumped elements with integrated components on a single substrate, yielding fabrication flexibility.