**1. Introduction**

336 Ultra Wideband – Current Status and Future Trends

Boston, Massachusetts, USA, Aug. , 2001.

D 76-80, USA, Sep - Oct , 2001.

2004.

[8] Das B , Das Ch.S. and S. Das S, "Interference Cancellation Schemes in UWB Systems used in Wireless Personal Area Network based on Wavelet based Pulse Spectral shaping and Transmitted Reference UWB using AWGN Channel Model ", International

[9] Hamalinen M., Hovinen V., Iinatti J., Latva-aho M., 2001: "In band Interference Power Caused by Different Kinds of UWB Signals at UMTS/WCDMA Frequency Bands", , the 2001 IEEE Radio and Wireless Conference, RAWCON 2001, pp. 97-100, Waltham-

[10] Hamalinen M., Iinatti J., Hovinen V., Latva-aho M., 2001," In band Interference of Three Kind of UWB Signals in GPS L1 Band and GSM900 Uplink Band", the 12th International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC2001, pp.

[11] Hamalainen M. , Hovinrn V. , Tesi R., Iinatti J. & Latava-aho M., 2002, " On the UWB System Coexistance with GSM900, UMTS/WCDMA, and GPS", IEEE Journal on

[12] Hamalinen M., Tesi R., Iinatti J.," UWB co-existence with IEEE802.11a and UMTS in modified Saleh-Valenzuela channel", Ultra Wideband Systems, 2004, pp. 45 – 49, May

[14] ITU Document 1-8/29-E, 2003, "Updating of Preleminary Study on Coexistance

Selected Areas in Communications, Vol. 20, No. 9, pp. 1712-1721.

[13] Holma H. , Toskala A., 2000, "WCDMA for UMTS", John Wiley & Sons.

Betwwen UWB and the Fixed Service in Band from 1 to 6 GHz".

Journal of Computer Applications Volume 2 – No.2, pp. 88.93, May 2010.

Since 2002, the Federal Communications Commission (FCC) authorized the use of ultra-wideband (UWB) signal transmissions for unlicensed use, in the range from 3.1 to 10.6 GHz, leading to a revived interest in research activities and to new opportunities for companies to explore and develop new broadband indoor and outdoor applications [1]. Moreover, UWB is seen as a promising technology for short range high speed wireless networks.

UWB signals are characterized by their huge bandwidth occupancy, high data rates, and very weak power density (−41.3 dBm/MHz), which gives them a noise-like signal characteristic, facilitating both interference mitigation and very low device power consumption. On the other hand, its very low intensity and high data rates limit the coverage to a few meters distance. Yet, by using radio-over-fiber (RoF) as a signal transportation technique, it is possible to deliver UWB signals over a fiber based network.

The radio-over-fiber (RoF) concept involves the transmission of RF signals by an optical fiber between a control station (CS) and a number of base stations (BSs). In the base stations, the RF signal is transmitted to end users by a wireless link. Integration of both optical and wireless broadband infrastructures into the same backhaul network leads to a significant simplification and cost reduction of BSs since all routing, switching and processing are shifted to the CS. This centralization of signal processing functions enables equipment sharing, dynamic allocation of resources, and simplified system operation and maintenance. The concept of RoF is shown in Figure 1 in an in-building network context.

RoF systems are (ideally) transparent to all signals transmitted in the optical fiber. It has been experimentally shown that RoF networks are well suited to simultaneously transport several wireless standards like wideband code division multiple access (WCDMA), IEEE 802.11 wireless local area network (WLAN) [2], global system for mobile communications

©2012 Oliveira et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0),which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ©2012 Oliveira et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Polymer optical fiber (POF) is an emerging medium for very short reach links. The popularity of polymer optical fiber is due to the advantages brought by its large core diameter and mechanical properties. These include connectorization simplicity due to the large numerical aperture, high tolerance to both misalignments and vibrations, low bending loss that eases

Performance Assessment of UWB-Over-Fiber and Applications 339

Common polymer optical fibers are based on polymethyl methacrylate (PMMA-POF). These fibers exhibit low bandwidth, multimodal dispersion and high attenuation (200 dB/km) hence are not suitable for today's high data rates or RoF systems where signals usually exhibit high bandwidths and high RF frequency carriers. Due to their relatively low bandwidth, a down-conversion of the RF signal to an intermediate frequency would be necessary, which introduces additional complexity and raises the cost of the BSs. Newer perfluorinated graded index polymer optical fiber (PF-GI-POF) from companies such as Sekisui Chemical, Chromis Fiber or Asahi Glass, solve this issue by combining a low attenuation material (about 50 dB/km @ 850 nm) with a graded index profile in their fiber construction. Bandwidth is relatively high for graded-index multimode fibers. Current PF-GI-POFs have bandwidth length products of around 1 GHz·Km, and attenuations as low as 10 dB/Km at 1310 nm [8]. In practical terms, for short links (< 100 m), it is limited by the response of directly modulated

Comparing to common silica multimode fiber (SI-MMF) with respect to transmission capacity, PF-GI-POF has the potential of high bandwidth and a lower modal dispersion. Moreover, it offers lower material dispersion and higher bandwidth than standard MMF with 40 Gb/s data

The attenuation is not an issue for short silica-based fiber link lengths. But in the case of POF the attenuation can be as high as 20 dB for the PMMA-POF or about 5 dB for the state of the art PF-GI-POF for a 100 m length link. Large-core glass fiber shows lower attenuation than POF, however their core size is restricted to 200 *μ*m due to the inherent inflexibility of glass. In this situation, POF again has advantages concerning easy handling and termination, tolerance to misalignments and high mechanical strength [10]. Furthermore, the typical large core of polymer fiber allows for large tolerance on misalignments that results in the possibility of using cheaper connectors. For comparison, consider the case of the power loss due to lateral (axial) misalignment of connecting two graded index (parabolic case) MMF with different core diameters. Comparing the power loss, assuming uniformly modal power distributions, for a misalignment of 25 *μ*m, yields a loss of 1.76 dB for a 62.5 *μ*m core diameter MMF whereas for the case of POF with a core diameter of 200 *μ*m, the same 25 *μ*m displacement results only in 0.48 dB loss [11]. New PF-GI-POF fibers being developed are able to withstand large temperature variation (−65 C to 125 C) and so may be suitable for applications in harsh critical environments. Their ease of installation, and tolerance to misalignment, vibration and large temperature variation operation makes these fibers suitable for short-range applications in the home environment or in critical applications such as the car and the avionics industry.

Here, we experimentally demonstrate the uplink of a MB-OFDM UWB signal (ECMA-368 standard [12]) over two different PF-GI-POFs from Chromis Fiberoptics using commercial UWB transceivers and cheap commercial off-the-shelf (COTS) components, namely an optical

transceiver composed by a low-cost 850 nm VCSEL and a PIN photodiode.

installation and simple and low maintenance costs due to its robustness.

laser devices [9].

transmission capability for 100 m links [9].

**Figure 1.** In-building radio-over-fiber concept.

(GSM) [3], WiMAX [4] and ultra-wide band (UWB) [5, 6]. Moreover, RoF systems also offer other attractive advantages such as low weight and immunity to electromagnetic interference. However, an optically modulated mm-wave signal can also suffer from several impairments namely nonlinear distortion, power penalty from the electric/optic/electric (E/O/E) conversion process, chromatic dispersion, attenuation from the optical fiber and phase noise from LASER sources.

Here we study the transmission performance of UWB over two distinctive optical networks. In Section 2, the packet error rate performnace in a low-cost multi-mode fiber (MMF) network composed by a 850 nm vertical-cavity surface emitting LASER (VCSEL) and a PIN photodiode connected by two different polymer optical fibers (POF) is assessed. Then, in Section 3, an analytical and experimental performance evaluation is carried out in a single-mode fiber (SMF) network composed by a reflective electro-absorption modulator (R-EAM) and a PIN photodiode.
