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.

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Abstract:In this paper, we evaluate experimentally and model theoretically the intra-and inter-core crosstalk between the polarized core modes in single-mode multi-core fiber media including temporal and longitudinal birefringent effects. Specifically, extensive experimental results on a four-core fiber indicate that the temporal fluctuation of fiber birefringence modifies the intra-and inter-core crosstalk behavior in both linear and nonlinear optical power regimes. To gain theoretical insight into the experimental results, we introduce an accurate multi-core fiber model based on local modes and perturbation theory, which is derived from the Maxwell equations including both longitudinal and temporal birefringent effects. Numerical calculations based on the developed theory are found to be in good agreement with the experimental data.

Single-wall carbon nanotube deposition on the cladding of optical fibers has been carried out to fabricate an all-fiber nonlinear device. Two different nanotube deposition techniques were studied. The first consisted of repeatedly immersing the optical fiber into a nanotube supension, increasing the thickness of the coating in each step. The second deposition involved wrapping a thin film of nanotubes around the optical fiber. For both cases, interaction of transmitted light through the fiber core with the external coating was assisted by the cladding mode resonances of a tilted fiber Bragg grating. Ultrafast nonlinear effects of the nanotube-coated fiber were measured by means of a pump-probe pulses experiment. © 2011 OCIS codes: 060.3735, 060.4370, 160.4236.Single-wall carbon nanotubes (SWNTs) have found innovative applications in the optical field due to their nonlinear properties in the near IR. Depending on the chirality of SWNTs, they can be either metallic or semiconducting, the latter being the desired behavior for nonlinear optical performance. Many optical applications could benefit from using SWNTs as nonlinear materials, such as noise suppression, wavelength conversion, and passive mode-locking [1][2][3]. A challenge when designing SWNT-based devices is incorporating the nanotubes in such a way as to enhance their interaction with light. One common method involves dispersing SWNTs in a solvent and spraying the solvent onto substrates in order to produce a nanotube film in the middle of a light beam [3]. Some inherent drawbacks in these configurations are the need for alignment and focusing stages, low SWNT burn thresholds, and low nonlinear interaction length. Solutions that overcome these challenges are based on SWNT deposition onto optical fibers. Tapered, D-shaped, and hollow optical fibers have been proposed to take advantage of the evanescent field interaction with SWNTs, distributing that interaction along the fiber length [4-6]. Nevertheless, manufacturing and handling these kinds of fibers is quite complex and delicate. In this work we propose for the first time SWNT deposition on standard optical fiber cladding for nonlinear applications. Interaction of light propagating through the fiber core with the outer SWNT coating is achieved via cladding mode resonances in a tilted fiber Bragg grating (TFBG). Two nanotube deposition methods have been carried out: dip-coating of the optical fiber in a SWNT suspension and wrapping of a SWNT film around the optical fiber. A TFBG is a kind of grating in which the index modulation planes are not orthogonal to the fiber axis but form a particular tilt angle. This inclination enhances the coupling of light from core mode to counterpropagating cladding mode resonances. Consequently, the grating transmission response is a multinotch response consisting of numerous cladding mode resonances in addition to the core mode resonance [see Fig. 1(a)]. The transverse mode profile of cladding modes spreads to the cladding of the fiber and interacts with the outer mediu...

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Abstract:The simultaneous transmission of four orthogonal frequencydivision multiplexing (OFDM)-based signals used to provide quintuple-play services along wavelength division multiplexing (WDM) long-reach passive optical networks (LR-PONs) is demonstrated experimentally. Particularly, the transmission performance of custom signal bearing Gigabit Ethernet data, Worldwide Interoperability for Microwave Access, Long Term Evolution and Ultra Wideband (sub-bands 2 and 3) signals is evaluated for different LR-PONs reaches, considering single-wavelength and WDM transmission, and using a centralized impairment compensation technique at the central office that is transparent to the services provided. It is shown that error vector magnitude-compliant levels are obtained for all the OFDM-based signals in WDM LR-PONs reaching 100 km and that negligible inter-channel crosstalk is obtained for a channel spacing of 100 GHz regardless the OFDM-based signal considered. The successful multi-format OFDM transmission along the 100 km-long WDM LR-PON is achieved in the absence of optical dispersion compensation or single sideband modulation, and it is enabled by the performance improvement provided by the centralized impairment compensation realized.

Supersymmetry (SUSY) has recently emerged as a tool to design unique optical structures with degenerate spectra. Here, we study several fundamental aspects and variants of one-dimensional SUSY in axially symmetric optical media, including their basic spectral features and the conditions for degeneracy breaking. Surprisingly, we find that the SUSY degeneracy theorem is partially (totally) violated in optical systems connected by isospectral (broken) SUSY transformations due to a degradation of the paraxial approximation. In addition, we show that isospectral constructions provide a dimension-independent design control over the group delay in SUSY fibers. Moreover, we find that the studied unbroken and isospectral SUSY transformations allow us to generate refractive-index superpartners with an extremely large phase-matching bandwidth spanning the S þ C þ L optical bands. These singular features define a class of optical fibers with a number of potential applications. To illustrate this, we numerically demonstrate the possibility of building photonic lanterns supporting broadband heterogeneous supermodes with large effective area, a broadband all-fiber true-mode (de)multiplexer requiring no mode conversion, and different mode-filtering, mode-conversion, and pulse-shaping devices. Finally, we discuss the possibility of extrapolating our results to acoustics and quantum mechanics.

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.