A FULL-DUPLEX RADIO-OVER-FIBER ARCHITECTURE USING DIFFERENTIALL PHASE-SHIFT KEYING SIGNALS FOR DOWNSTREAM AND REMODULATED OOK FOR UPSTREAM

Radio-over-Fiber (ROF) is a promising technology to achieve future broadband access requirements with reliability, transparency and flexibility. We propose a novel full-duplex bi-directional radio-over-fiber (ROF) system transmitting 10 Gb/s differential phase-shift keying (DPSK) signals at the central office (CO) for downstream and ON–OFF keying (OOK) re-modulation of the downlink carrier at the base station (BS) for upstream. As the same optical carrier is used for both uplink and downlink, no additional light source is required at the BS, which significantly reduces the cost, improves the wavelength utilization efficiency and simplifies the overall system. The simulation results show that the downstream 10 Gb/s DPSK data and the upstream 1Gb/s OOK data can transmit over 50km single-mode fiber successfully without dispersion compensation. The results show that this scheme provides a practical solution to meet the data rate and cost requirement of tomorrow’s ROF access networks

A WDM-PON with DPSK modulated downstream and OOK modulated upstream signals based on symmetric 10 Gbit/s wavelength reused bidirectional reflective SOA

We investigate a wavelength-division-multiplexing passive optical network (WDM-PON) with centralized lightwave and direct detection. The system is demonstrated for symmetric 10 Gbit/s differential phase-shift keying (DPSK) downstream signals and on-off keying (OOK) upstream signals, respectively. A wavelength reused scheme is employed to carry the upstream data by using a reflective semiconductor optical amplifier (RSOA) as an intensity modulator at the optical network unit (ONU). The constant-intensity property of the DPSK modulation format can keep high extinction ratio (ER) of downstream signal and reduce the crosstalk to the upstream signal. The bit error rate (BER) performance of our scheme shows that the proposed 10 Gbit/s symmetric WDM-PON can achieve error free transmission over 25-km-long fiber transmission with low power penalty

Wavelength division multiplexing passive optical networks (WDM PONs) with downstream DPSK and upstream remodulated OOK using injection-locked Fabry-Perot laser diodes (FP-LDs)

Wavelength Division Multiplexing-Passive Optical Network (WDM-PON) system based on the injection locked Fabry-Perot laser diode (FP-LD) has been investigated. The system has been demonstrated without dispersion compensation for both 10Gbps Differential phase-shift keying (DPSK) downstream signal and 2.5 Gbps On-off keying (OOK) upstream signal respectively. Error free transmission over 50-km is achieved by tailoring the parameters of the FP-LD. The BER performance of our system shows that the injection locked FP-LD is a low cost effective colourless transmitter for high-speed WDM-PONs

Bidirectional OFDM-WDM-PON System Employing 16-QAM Intensity Modulated OFDM Downstream and OOK Modulated Upstream

We have investigated an orthogonal frequency-division multiplexing (OFDM) wavelength-division-multiplexing (WDM) passive optical network (PON) with centralized lightwave and direct detection. The system was demonstrated for both 10 Gbps 16 quadrature amplitude modulation (16-QAM) intensity-modulated OFDM downstream signals and 2.5 Gbps On-off keying (OOK) upstream signals respectively. A wavelength-reuse scheme is employed to carry the upstream data by using a mach-zehnder modulator (MZM) as an intensity Modulator at the optical network unit (ONU). The proposed scheme offers a promising solution for future PONs

Coherent 16 Quadrature Amplitude Modulation (16QAM) Optical Communication Systems

Coherent optical fiber communications for data rates of 100Gbit/s and beyond have recently been studied extensively primarily because high sensitivity of coherent receivers could extend the transmission distance. Spectrally efficient modulation techniques such as M-ary quadrature amplitude modulation (M-QAM) can be employed for coherent optical links. The integration of multi-level modulation formats based on coherent technologies with wavelength-division multiplexed (WDM) systems is key to meet the aggregate bandwidth demand. This paper reviews coherent 16 quadrature amplitude modulation (16QAM) systems to scale the network capacity and maximum reach of current optical communication systems to accommodate traffic growth

Contribution a l'etude de la vegetation dans le Baer-Bassit et le Djebel Alaouite de Syrie

The Baer-Bassit and Alaouite Mountains are in north-west Syria. The Jebel Alaouite is composed of Jurassic and Cretaceous calcareous rocks, running north-south and culminating on 1580 m. The Baer-Bassit is hilly country with green rocks.The climate is of Mediterranean type. Soil genesis and classification and degradation by the action of man were studied. Nahal. related soil characteristics to the vegetation. The flora already showed its most prominent traits in the Pliocene. The pluvial periods during the Quaternary influenced its distribution; their effect was still visible.Directions were worked out for the rational management and exploitation of the forests of Pinus brutia Ten., still in good condition, and the re-establishment of remnant forests of Abies cilicica (Ant. et Ky.) and Cedrus libani A. Rich.The work closed with a synsystematic and synecological study of the most important tree association of Syria, the Pistacieto-Quercetum calliprini. The importance of the progressive and regressive phases of photodynamic successions for the forester was pointed out

Comparison between OQPSK and DPSK bidirectional radio over fiber transmission systems

Radio over fiber is becoming an increasingly important technology for the wireless market since it introduces a higher data transmission rate and large bandwidth. In this paper, we have compared OQPSK and DPSK bidirectional radio over fiber ROF systems, where an offset quadrature phase shift keying (OQPSK) or differential phase shift keying (DPSK) signals are used for down-link and an on-off keying (OOK) signal re-modulated for up-link. Several measurements were performed including Bit Error Rate (BER) curves for uplink and downlink, RSOA gain curve and noise figure with the variation of input power and temperature for each system

Applications of active arrayed-waveguide grating in future wavelength division multiplexing networks

The role of active arrayed-waveguide gratings (AWGs) in future dynamic wavelength-division multiplexing (WDM) networking and routing is investigated. Simulations are done using the beam propagation method (BPM). The results indicate that active AWGs can be used in multiple-channel control with an SNR up to 19 dB and dynamic dispersion compensation of up to 160 ps/nm

Thulium Doped Fiber Amplifier (TDFA) for S-band WDM Systems

A comprehensive numerical model based on solving rate equations of a thulium-doped silica-based fiber amplifier is evaluated. The pump power and thulium-doped fiber (TDF) length for single-pass Thulium-Doped Fiber Amplifiers (TDFA) are theoretically optimized to achieve the optimum Gain and Noise Figure (NF) at the center of S-band region. The 1064 nm pump is used to provide both ground-state and excited state absorptions for amplification in the S-band region. The theoretical result is in agreement with the published experimental result

Multistage WDM access architecture employing cascaded AWGs

Here we propose passive/active arrayed waveguide gratings (AWGs) with enhanced performance for system applications mainly in novel access architectures employing cascaded AWG technology. Two technologies were considered to achieve space wavelength switching in these networks. Firstly, a passive AWG with semiconductor optical amplifiers array, and secondly, an active AWG. Active AWG is an AWG with an array of phase modulators on its arrayed-waveguides section, where a programmable linear phase-profile or a phase hologram is applied across the arrayed-waveguide section. This results in a wavelength shift at the output section of the AWG. These architectures can address up to 6912 customers employing only 24 wavelengths, coarsely separated by 1.6 nm. Simulation results obtained here demonstrate that cascaded AWGs access architectures have a great potential in future local area