Search

An advanced low cost bidirectional wavelength-division-multiplexing hybrid fiber-wired/fiber-wireless/fiber-VLC/fiber-IVLC transmission system based on a self-seeded InP based quantum dash-laser diode (QD-LD) and reflective semiconductor amplifier (RSOA) is proposed and experimentally demonstrated. In this paper, 10 Gbps/50 GHz MMW and 10 Gbps/100 GHz MMW over 50-km SMF as well as 40-m optical and 10-m radio-frequency (RF) wireless link, and 10 Gbps baseband (BB) data stream over 50-km SMF are successfully transmitted by employing self-injection locking scheme on QD-LD in downlink. RSOA is utilized at the receiving site to broadcast 2.5 Gbps data signal over 50-km SMF plus 10-m free-space link in uplink by reusing the carrier, that makes the system cost-effective. High receiver sensitivity and signal-to-noise ratio (SNR), low bit-error-rate (BER) and low error vector magnitude (EVM), and excellent eye-diagrams in our proposed network build the system more reliable and stable with acceptable performance. Therefore, proposed hybrid transmission system could become prominent alternative not only for progressive fiber backbone network but also for RF/optical wireless feeder networks. [ABSTRACT FROM AUTHOR]

The next generation of optical access communication networks that support 100 Gbps and beyond, require advances in modulation schemes, spectrum utilization, new transmission bands, and efficient devices, particularly laser diodes. In this paper, we investigated the viability of new-class of InAs/InP Quantum-dash laser diode (Qdash-LD) exhibiting multiple longitudinal light modes in the L-band to carry high-speed data rate for access network applications. We exploited external and self injection-locking techniques on Qdash-LD to generate large number of stable and tunable locked modes, and compared them. To stem the capability of each locked mode as a potential subcarrier, data transmission is carried out over two mediums; single mode fiber (SMF) and free space optics (FSO) to emulate real deployment scenarios of optical networks. The results showed that with external-injection locking (EIL), an error-free transmission of 100 Gbps dual polarization quadrature phase shift keying (DP-QPSK) signal is demonstrated over 10 km SMF and 4 m indoor FSO channels, with capability of reaching up to 128 Gbps, demonstrated under back-to-back (BTB) configuration. On the other hand, using self-injection locking (SIL) scheme, a successful data transmission of 64 Gbps and 128 Gbps DP-QPSK signal over 20 km SMF and 10 m indoor FSO links, respectively, is achieved. [ABSTRACT FROM AUTHOR]

We investigate the thermal characteristics of multi-stack chirped barrier thickness InAs/InGaAlAs/InP quantum-dash-in-a-well lasers of different ridge widths 2, 3, 4 and 15 µm. The effect of varying this geometrical parameter on the extracted thermal resistance and characteristic temperature, and their stability with temperature are examined. The results show an inverse relation of ridge-width with junction temperature with 2 µm device exhibiting the largest junction temperature buildup owing to an associated high thermal resistance of ∼45 °C/W. Under the light of this thermal analysis, lasing behavior of different ridge-width quantum-dash (Qdash) lasers with injection currents and operating temperatures, is investigated. Thermionic carrier escape and phonon-assisted tunneling are found to be the dominant carrier transport mechanisms resulting in wide thermal spread of carriers across the available transition states of the chirped active region. An emission coverage of ∼75 nm and 3 dB bandwidth of ∼55 nm is exhibited by the 2 µm device, thus possibly exploiting the inhomogeneous optical transitions to the fullest. Furthermore, successful external modulation of a single Qdash Fabry-Perot laser mode via injection locking is demonstrated with eye diagrams at bit rates of 2–12 Gbit/s incorporating various modulation schemes. These devices are being considered as potential light sources for future high-speed wavelength-division multiplexed optical communication systems. [ABSTRACT FROM AUTHOR]

Quantum dashes were synthesized in the molecular beam epitaxial growth of InAs on GaAs(2 2 1). By changing the arsenic pressure it was possible to obtain highly ordered one-dimensional InAs arrays as demonstrated by autocorrelation function analysis. Polarized Raman spectroscopy was utilized in order to characterize the samples and to estimate the stress at the InAs/GaAs interface as well as the surface anisotropy imposed by the quasi one-dimensional character of the quantum dashes. The most ordered surface, showed the lowest correlation length, and for this sample the Raman spectra exhibits small shift of the GaAs resonance modes indicating likewise small GaAs tensile strain. [ABSTRACT FROM AUTHOR]

Abstract: This paper treats the impact of post growth tuned InAs/InP quantum dashes' (QDas) size/composition distribution on carriers' localization and thermal redistribution. The spread of this distribution depends on the experimental conditions used for the phosphorus ion implantation enhanced intermixing process. Atypical temperature-dependent luminescence properties have been observed and found to be strongly dependent on the amount of QDas size/composition dispersion. The experimental results have been reproduced by a model that takes into account the width of the QDas localized states distribution and consequent thermally induced carriers' redistribution. This model gives critical temperature values marking the beginning and the end of carriers delocalization and thermal transfer processes via an intermixing induced carrier's transfer channel located below the wetting layer states. [Copyright &y& Elsevier]