The use of ultra-wide band (UWB) radio technique is proposed as a viable solution for the distribution of highdefinition audio/video content in fiber-to-the-home (FTTH) networks. The approach suitability is demonstrated by the transmission of standards-based UWB signals at 1.25 Gbit/s along different FTTH fiber links with 25 km up to 60 km of standard single-mode fiber length in a laboratory experiment. Experimental results suggest that orthogonal frequency division multiplexed UWB signals exhibit better transmission performance in FFTH networks than impulse radio UWB signals. Index Terms-Optical communications, Fiber-To-The-Home access networks, Ultra-Wide Band (UWB). I. INTRODUCTION ltra-Wide Band (UWB) has been indicated as one of the most promising techniques to be used in wireless communication networks. The growing interest in this technique is due to its low self-interference, tolerance to multipath fading, low probability of interception and capability of passing through walls while maintaining the communication [1]. Nowadays, UWB is appointed for high bit-rate wireless communications at picocell range, namely as a replacement of high definition (HD) video/audio cabling [2]. This paper proposes to extend this application to the distribution of HD audio/video content by the optical modulation and transmission of UWB signals in their native format through fiber-to-the-home (FTTH) access networks. This approach exhibits several advantages: (i) FTTH networks provide bandwidth enough to distribute a large number of UWB signals, as each one of them can occupy up to 7 GHz in current UWB regulation [3]. (ii) No trans-modulation is required at user premises. HD audio/video content is transmitted through the fibers in UWB native format. (iii) No frequency up-conversion is required at customer premises. The UWB signals are photo-detected, filtered, amplified and radiated directly to establish the wireless connection. (iv) FTTH networks are transparent to the specific UWB implementation Manuscript received 6th December 2007.
The photonic generation of electrical orthogonal frequency-division multiplexing (OFDM) modulated wireless signals in the 75j110 GHz band is experimentally demonstrated employing in-phase/quadrature electrooptical modulation and optical heterodyn upconversion. The wireless transmission of 16-quadrature-amplitude-modulation OFDM signals is demonstrated with a bit error rate performance within the forward error correction limits. Signals of 19.1 Gb/s in 6.3-GHz bandwidth are transmitted over up to 1.3-m wireless distance. Optical comb generation is further employed to support different channels, allowing the cost and energy efficiency of the system to be increased and supporting different users in the system. Four channels at 9.6 Gb/s/ch in 14.4-GHz bandwidth are generated and transmitted over up to 1.3-m wireless distance. The transmission of a 9.6-Gb/s singlechannel signal occupying 3.2-GHz bandwidth over 22.8 km of standard single-mode fiber and 0.6 m of wireless distance is also demonstrated in the multiband system.
We propose and analyze a novel (to our knowledge) approach to implement the spectral self-imaging effect of optical frequency combs. The technique is based on time-domain multilevel phase-only modulation of a periodic optical pulse train. The method admits both infinite-and finite-duration periodic pulse sequences. We show that the fractional spectral self-imaging effect allows one to reduce by an integer factor the comb frequency spacing. . In the frequency domain, a periodic pulse train is described by an optical frequency comb with frequency spacing equal to the pulse repetition rate, i.e., f rep ¼ 1=T rep , as shown in Fig. 1(a). Similarly, the spectral self-imaging effect, or spectral Talbot effect, occurs when a periodic sequence of pulses is globally chirped by an optical phase-only modulator with a quadratic time-domain response. Under specific temporal chirping conditions, the comb frequency spacing is reduced by an integer factor while the comb envelope is unchanged, as shown in Fig. 2(a). For other chirping conditions, a frequency shifting effect is observed in the frequency comb. The first proposal on these spectral Talbot effects [5] assumed a particular chirping mechanism based on cross-phase modulation with a long Gaussian pump pulse. This approach, however, only admits periodic pulse sequences with limited time duration, due to the intrinsic finite extent of the chirping effect produced by the long Gaussian pump pulse.In this Letter, we propose a novel approach for the practical implementation of the spectral self-imaging effect. The technique requires the time-domain multishift phase modulation of an input pulse train. This phenomenon exhibits interesting features, including tunability in comb frequency spacing and the ability of comb frequency shifting, which can find practical application in optical communications [6] and optical signal processing [7]. Our theoretical proposal is confirmed by numerical simulations.First, let us assume the propagation of a periodic pulse train through a general quadratic phase-only optical filter, described by the spectral transfer function HðωÞ ¼ expðiΦ 2 ω 2 =2Þ, where Φ 2 is the so-called group delay dispersion coefficient [2]. When the value of Φ 2 verifies the well-known temporal Talbot condition [2],an undistorted and multiplied copy of the initial pulse train is obtained. In this expression, s and r are mutually prime integer numbers , and ω rep ¼ 2πf rep is the repetition rate of the original pulse train. The pulse multiplication factor is given by the integer r. In Fig. 1(a), we schematically show an example of the temporal Talbot effect with r ¼ 2. Fig. 1. Illustration of the temporal Talbot effect using (a) a quadratic phase-only filter and (b) line-by-line phase-only filtering. In both cases, two-times repetition-rate multiplication is shown, i.e., r ¼ 2 [Eqs. (1) and (2), respectively].
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