Showing papers on "Wavelength-division multiplexing published in 2003"

Optical regeneration at 40 Gb/s and beyond

Abstract: As optical amplifiers have opened new perspectives for optical communication systems with ultrahigh capacities and long-haul transmission distances (more than 1 Tb/s over 10 000 km), fundamental limits are being felt. In order to overcome these propagation impairments, another technology revolution is soon required. Promising developments concern in-line all-optical regeneration, which makes it possible to transmit optical data over virtually unlimited distances. In this paper, we recall the basic principles of optical regeneration in optical communication systems and review the current technology alternatives foreseen for future 40-Gb/s transmission system implementation, as investigated in Alcatel Research and Innovation. The alternative offered by optoelectronic regeneration is also discussed, so as to identify and highlight the advantages of the all-optical approach.

Parametric amplifiers driven by two pump waves

Abstract: Parametric amplifiers (PAs) are well-suited for optical communication systems. Not only can PAs provide high gain for arbitrary signal wavelengths, they can also conjugate the signals and convert their wavelengths. The four-sideband model of parametric amplifiers driven by two pump waves will be reviewed and used to describe the conditions required to produce broad-bandwidth gain. The flexibility of the two-pump architecture allows it to produce gain that is nearly independent of the signal polarization, and idlers whose spectral widths are comparable to that of the signal.

An optical network unit for WDM access networks with downstream DPSK and upstream remodulated OOK data using injection-locked FP laser

Abstract: We investigate the use of optical differential phase-shift keying (DPSK) as the downstream modulation format in a low-cost upstream data remodulation scheme for a wavelength-division multiplexing (WDM)-based passive optical network. A 2.5-Gb/s upstream data transmitter is realized by directly modulating a Fabry-Perot (FP) laser, injection-locked with a 10-Gb/s downstream optical DPSK signal. A simple polarization-offset technique is proposed to largely minimize the induced power penalty.

Fast optical wavelength interrogator employing arrayed waveguide grating for distributed fiber Bragg grating sensors

Abstract: A new type of interrogator for distributed fiber Bragg grating (FBG) sensors that employs an arrayed waveguide grating (AWG) is proposed and its operating features are in detail investigated both theoretically and experimentally. The remedy for achieving the linear characteristics of wavelength detection as well as for insuring the reliable and environmentally stable operation of interrogation is proposed and its usefulness is demonstrated in good agreement with the experimental results. The developed interrogator consists of a fully passive, small, all-solid, rugged optical IC and can detect wavelengths of a great number of FBG sensors with high precision better than 0.5 pm and high speed.

Rational design of organic electro-optic materials

Abstract: Quantum mechanical calculations are used to optimize the molecular first hyperpolarizability of organic chromophores and statistical mechanical calculations are used to optimize the translation of molecular hyperpolarizability to macroscopic electro-optic activity (to values of greater than 100 pm V−1 at telecommunications wavelengths). Macroscopic material architectures are implemented exploiting new concepts in nanoscale architectural engineering. Multi-chromophore-containing dendrimers and dendronized polymers not only permit optimization of electro-optic activity but also of auxiliary properties including optical loss (both absorption and scattering), thermal and photochemical stability and processability. New reactive ion etching and photolithographic techniques permit the fabrication of three-dimensional optical circuitry and the integration of that circuitry with semiconductor very-large-scale integration electronics and silica fibre optics. Electro-optic devices have been fabricated exploiting stripline, cascaded prism and microresonator device structures. Sub-1 V drive voltages and operational bandwidths of greater than 100 GHz have been demonstrated. Both single-and double-ring microresonators have been fabricated for applications such as active wavelength division multiplexing. Free spectral range values of 1 THz and per channel modulation bandwidths of 15 GHz have been realized permitting single-chip data rates of 500 Gb s−1. Other demonstrated devices include phased array radar, optical gyroscopes, acoustic spectrum analysers, ultrafast analog/digital converters and ultrahigh bandwidth signal generators.

DWDM 40 G transmission over trans-Pacific distance (10,000 km) casing CSRZ-DPSK, enhanced FEC and all-Raman amplified 100 km UltraWave/spl trade/ fiber spans

Abstract: We demonstrate error-free dense-wavelength-division multiplexing (DWDM) transmission of 40 40-Gb/s channels with 100-GHz spacing over 10 000 km dispersion-managed fiber using carrier-suppressed return-to-zero differential-phase-shift keying (CSRZ-DPSK), enhanced foward-error correction, and all-Raman-amplified spans with 100-km terrestrial length.

Wavelength channel data rewrite using saturated SOA modulator for WDM networks with centralized light sources

Abstract: This paper describes a method for realizing the efficient utilization of wavelength resources in wavelength-division multiplexing networks with centralized light sources. Using a deeply saturated semiconductor optical amplifier (SOA) modulator located in a remote node (RN), we erase the data on a downstream signal with a low extinction ratio and modulate it with new data to generate an upstream signal. Thus, we use only one wavelength for bidirectional transmission between a center node and an RN, without placing lasers at the RN. In this paper, we analyze the data suppression characteristic of the SOA using a large signal model. We also estimate the bit error rate degradation in the presence of an unsuppressed downstream bit pattern in an upstream signal. We then report experimental results that confirm the basic characteristics of the wavelength channel data rewriter, which we constructed using a linear amplifier and an SOA. Finally, we provide the results of a data transmission experiment that we undertook using the data rewriter.

Multiwavelength Raman fiber-ring laser based on tunable cascaded long-period fiber gratings

Abstract: Multiwavelength Raman fiber lasers using intracavity tunable cascaded long-period fiber gratings (LPFGs) are discussed. The application of the cascaded LPFGs as a multichannel fiber filter for the multiple-wavelength generation is proposed and experimentally demonstrated. The characteristics of multiwavelength fiber-ring lasers can be controlled by changing the physical parameters of cascaded LPFGs such as the separation distance between the gratings, grating length, and number of gratings. The multiwavelength Raman fiber-ring laser with nine wavelength-division-multiplexing channels with 100-GHz spacing and 19 channels with 50-GHz spacing has been achieved by varying the physical parameters of cascaded LPFGs.

Optical carrier supply module using flattened optical multicarrier generation based on sinusoidal amplitude and phase hybrid modulation

Abstract: This paper presents an optical carrier supply module (OCSM) that functions as a common multicarrier light source, a wavelength bank, for superdense wavelength-division multiplexing (SD-WDM) networks that utilize a large number of wavelengths with narrow channel spacing. A novel sideband generator based on a sinusoidal amplitude-phase hybrid modulation scheme is the key technique. The sideband generator generates nine flattened optical sidebands within 3 dB from one seed light source, and the input from wavelength-division multiplexing (WDM) seed carriers expands the number of generated sidebands. Scalability against the number of wavelengths is achieved by increasing the number of seed carriers used. The SD-WDM system employing OCSM reduces the number of laser diodes (LDs) and attendant wavelength monitoring/stabilization circuits. Multiple distributions to SD-WDM networks by splitting the OCSM output can promote this effect. We designed OCSM and experimentally investigated its performance pertaining to the electrical signal-to-noise ratio (SNR) of the OCSM output. The experimental results show the wavelength scalability to 1000 channels. We also developed an OCSM prototype that generated 12.5-GHz-spaced 256-channel WDM carriers. All the generated carriers exhibit the electrical SNR of more than 31.5 dB at 2.5 Gb/s and the power flatness of within 3 dB. The distribution over 100 SD-WDM networks is experimentally confirmed.

Optical switch fabrics for ultra-high-capacity IP routers

Abstract: Next-generation switches and routers may rely on optical switch fabrics to overcome scalability problems that arise in sizing traditional electrical backplanes into the terabit regime. In this paper, we present and discuss several optical switch fabric technologies. We describe a promising approach based on arrayed waveguide gratings and fast wavelength tuning and explain the challenges with respect to technical and commercial viability. Finally, we demonstrate an optical switch fabric capable of 1.2-Tb/s throughput and show packet switching with four ports running at 40 Gb/s each.

Ultra-wide-band tellurite-based fiber Raman amplifier

Abstract: We describe the first wide-band tellurite-based fiber Raman amplifier (T-FRA) for application to seamless ultra-large-capacity dense wavelength-division multiplexing (WDM) systems. First, we confirmed that the Raman scattering characteristics of the tellurite-based fiber has so large a gain coefficient and Stokes shift that we can achieve a wide-band tellurite-based fiber Raman amplifier with a shorter fiber length than when using silica-based fiber. Second, we investigated the small signal gain and the signal transmission characteristics for a high gain and high output power operation with a single-stage amplifier. Focusing on double Rayleigh scattering, we compared the high gain limit of tellurite- and silica-based fibers. We then studied the impact of nonlinear effects by measuring the bit error rate (BER) when using a two-stage amplifier with a high output power of 18.8 dBm in which we simultaneously amplified eight channel signals in the L-band located on the ITU 100-GHz grid. Finally, we designed a wide-band tellurite-based fiber Raman amplifier with a multiwavelength band pumping scheme. We constructed this amplifier with a tellurite-based fiber only 250 m in length pumped by four-wavelength-channel laser diodes, and it provided a 160-nm bandwidth with a gain of over 10 dB and a noise figure below 10 dB from 1490 to 1650 nm. We also measured the BER to confirm the transmission characteristics of the amplifier for single channel operation over the whole signal wavelength range of 160 nm. We thus confirmed that the amplifier could be employed in ultra-high-capacity WDM systems.

A self-protected architecture for wavelength-division-multiplexed passive optical networks

Abstract: We propose a novel network architecture for wavelength-division-multiplexed passive optical networks which can provide bidirectional 1:1 protection against any fiber cut between the remote node and the optical network units (ONUs). In case of such fiber cut, the affected ONU can still communicate with the optical line terminal by rerouting the wavelength channels via the adjacent ONU.

Ring-resonator filters in silicon oxynitride technology for dense wavelength-division multiplexing systems.

Abstract: The design and characterization of ring-resonator-based filters with free spectral ranges of 100 and 50 GHz by use of SiO(x)N(y) technology is presented. Fiber-to-fiber insertion losses of 4.4 dB on the drop port and 2.1 dB on the through port have been achieved for a single-ring filter. An interleaver filter for a 25-GHz spaced dense wavelength-division multiplexing system with two cascaded rings is demonstrated. The filter has a 7.4-GHz bandwidth at -1 dB and an extinction ratio of 15 dB and is polarization independent.

The benefits of ultrashort optical pulses in optically interconnected systems

Abstract: Many properties of an optically interconnected system can be improved through the use of a modelocked laser. The short pulse duration, high peak power, wide spectral bandwidth, and low timing jitter of such a laser lead to these benefits. Timing advantages include simplified synchronization across large chip areas, receiver latency reduction, and data resynchronization. Lower power dissipation may be achieved through improved receiver sensitivity. Additional applications of short optical pulses include time-division multiplexing, single-source wavelength-division multiplexing, and precise time-domain testing of circuits. Several of these concepts were investigated using a high-speed chip-to-chip optical interconnect demonstration link. The link employs a modelocked laser and surface-normal optoelectronic modulators that were flip-chip bonded to silicon CMOS circuits. This paper outlines experiments that were performed on or simulated for the link, and discusses the important benefits of ultrashort optical pulses for optical interconnection.

Amplification of WDM signals in fiber-based optical parametric amplifiers

Abstract: We demonstrate for the first time, experimentally, the performance of fiber-based optical parametric amplifiers in wavelength-division-multiplexed (WDM) applications. Both a 3 /spl times/ 10 Gb/s and a commercial 7 /spl times/ 2.5 Gb/s WDM system are investigated together with the parametric amplifier. Limitations due to pump depletion and four-wave mixing are quantified. Measurements showing the performance in terms of power penalty and gain versus input-output signal power are presented.

Performance evaluation of TCP over optical burst-switched (OBS) WDM networks

Abstract: This paper studies the performance of TCP transport protocol over an optical burst-switched (OBS) wavelength division multiplexed (WDM) wide-area network. Typically, an OBS network consists of optical core routers and electronic edge routers connected by WDM links. At the network ingress nodes, IP packets are assembled into bursts that are routed through the core network and disassembled at the network egress nodes. This paper studies the effects of OBS network characteristics and parameters on TCP's delay and throughput performance: (i) burstification (burst-assembly and disassembly) delays, (ii) data-burst scheduling and (iii) variation of burst packet parameters (i.e. burst size, burst time-outs), and (iv) burst drop probability. Detailed results based on an ns2-based simulator, that has been extended to incorporate WDM and OBS networking, are presented.

Photonic analog-to-digital converter using soliton self-frequency shift and interleaving spectral filters.

Abstract: We propose a novel ultrafast photonic analog-to-digital converter that uses the soliton self-frequency shift in an optical fiber as an optical power-to-frequency conversion mechanism and a set of interleaving spectral filters as the optical comparators. Our method does all the signal processing in the optical domain and requires binary receivers in only the electronic domain. In contrast to the usual exponential scaling, the simultaneous binary search architecture that we propose results in a flash analog-to-digital converter with remarkable linear scaling between the number of comparators and the number of bits resolved.

A widely tunable high-speed transmitter using an integrated SGDBR laser-semiconductor optical amplifier and Mach-Zehnder modulator

Abstract: The first integrated sampled-grating distributed Bragg reflector (SGDBR) laser-semiconductor optical amplifier-Mach-Zehnder modulator transmitter is presented. Devices have 3 dB bandwidth ranging from 13-18 GHz corresponding to electrodes lengths that range between 200-300 /spl mu/m long. This corresponds to a V/sub pi/ of 4.8-6.2 V.

Transmission of 25-Gb/s RZ-DQPSK signals with 25-GHz channel spacing over 1000 km of SMF-28 fiber

Abstract: We report transmission of nine 25-Gb/s return-to-zero differential quadrature phase-shift keyed (RZ-DQPSK) dense wavelength-division-multiplexing signals with 25-GHz channel spacing over 1000 km of single-mode fiber (SMF-28) in a recirculating loop. The loop uses all erbium-doped fiber amplifiers (EDFAs) and has an amplifier spacing of 100 km with an average loss of 25 dB between EDFAs and a maximum span loss of up to 30 dB. All channels were copolarized launched. No precompensation or postcompensation was employed. To the best of our knowledge, this is the first transmission test of multichannel RZ-DQPSK signals operating at 25 Gb/s with a spectral efficiency of 0.8 b/s/Hz. The transmission distance is limited by amplified spontaneous emission noise due to the high span losses. Nevertheless, our result indicates that upgrading the capacity of long-haul terrestrial systems using RZ-DQPSK modulation format should be feasible.

High spectral efficiency 1.6-b/s/Hz transmission (8 x 40 Gb/s with a 25-GHz grid) over 200-km SSMF using RZ-DQPSK and polarization multiplexing

Abstract: With relatively simple standard transmission equipment, we achieved a wavelength-division-multiplexing transmission with a record-high spectral efficiency of 1.6 b/s/Hz using return-to-zero differential quadrature phase-shift keying and polarization multiplexing over 200-km standard single-mode fiber with a 40-Gb/s capacity per wavelength but 10-GSymbol/s rate.

Analysis and control of transient dynamics of EDFA pumped by 1480- and 980-nm lasers

Abstract: The transient responses of Er-doped fiber amplifier (EDFA) to fast channel adding/dropping processes have been studied and analyzed. The result shows that the speed in which we can control EDFA with a feedback circuit is limited by the physical processes involved in the amplification. We demonstrated that with the combination of electrical feedforward and feedback, the power excursion caused by fast channel adding/dropping processes can be minimized.

Demultiplexing using an arrayed-waveguide grating for frequency-interleaved DWDM millimeter-wave radio-on-fiber systems

Abstract: The frequency-interleaved dense- wavelength-division-multiplexing (DWDM) millimeter-wave (mm-wave) radio-on-fiber is an indispensable technique to improve the optical spectrum efficiency. We propose possible configurations of multiplexing and demultiplexing (DEMUX) schemes using an arrayed-waveguide grating (AWG) with two input and N output waveguides (N: total channel number). In this paper, we focus on the DEMUX scheme and experimentally demonstrate the DEMUX scheme using a commercially available AWG. In the experiment, 25-GHz-separated two-channel optical double sideband signals modulated by a 60-GHz millimeter-wave carrying a 156-Mb/s data are optically multiplexed by the frequency interleaving. The power penalty after DEMUX, which was due to interchannel interference, was less than 0.5 dB. We also made a transmission experiment over 25-km standard single-mode fiber (SMF). No noticeable power penalty in the received data due to chromatic dispersion of the transmission fiber was observed. This is because only the carrier and a sideband are detected in the proposed DEMUX scheme.

High-density optical interconnects within large-scale systems

Abstract: Next-generation high-end data processing systems such as Internet switches or servers are approaching aggregate bandwidths in excess of 1 Terabit per second. In the case of Internet switches, the increase of fiber bandwidth that is caused by the introduction of Dense Wavelength Division Multiplexing leads to an increase of system size from single-shelf to multi-rack configurations. Intra-system interconnects will therefore span from centimeters (on-board) up to tens of meters (rack-to-rack). The task of providing hundreds of individual links at speeds in excess of 10 Gigabit per second over these distances becomes increasingly difficult for conventional copper-based technology. Using a packet switch system as an example application, we define a set of interconnect requirements for future large-scale systems. Distinguishing three interconnect classes (on-board, card-to-card over a backplane, rack-to-rack), we study the expected limits of copper-based solutions from an application point of view. After an overview of the state of the art in optical interconnect technology, we compare available technologies with the initially defined requirements. From this, we deduct key focus areas for future optical interconnect research. Finally, we present some of our recent activities in the field of waveguide and free-space based board-to-board interconnects.

Bidirectional WDM passive optical network for simultaneous transmission of data and digital broadcast video service

Abstract: We have demonstrated an easily upgradable bidirectional passive optical network for the simultaneous transmission of wavelength-division-multiplexing channels and digital broadcast video signals. The proposed network could transmit 15 2.5-Gb/s downstream channels, 15 155-Mb/s upstream channels, and one broadcast signal consisting of more than 70 digital video channels.

Optical heterodyne detection technique for densely multiplexed millimeter-wave-band radio-on-fiber systems

Abstract: Even in millimeter-wave-band (mm-wave-band) radio-on-fiber (ROF) systems, wavelength-division multiplexing (WDM) combined with subcarrier multiplexing (SCM) is a practical and attractive way to increase the channel capacity in existing optical-frequency-interleaved fibers. In this paper, we propose a channel selection scheme for interleaved dense WDM/SCM mm-wave-band ROF signals that use optical heterodyne detection with dual-mode local light. The principle underlying this scheme is explained theoretically, and channel selection of the DWDM/SCM ROF signal after transmission over a 25-km-long standard single-mode optical fiber has been experimentally demonstrated.

STOLAS: switching technologies for optically labeled signals

Abstract: GMPLS-based labeled optical burst switching (LOBS) networks are being considered as the next-generation optical Internet. GMPLS includes wavelength switching next to label and fiber (space) switching. We present a new concept of optically labeling bursts of packets suitable for LOBS networks supported by GMPLS. It is based on angle modulation, which enables control information to modulate the phase or frequency of the optical carrier, while payload data are transmitted via intensity modulation (IM). In particular, the optical label is orthogonally modulated, with respect to the payload, using either frequency shift keying or differential phase shift keying. We present a performance analysis of the modulation schemes by means of simulations where the influence of the payload IM extinction ratio and laser linewidth are investigated. In addition, the transmission performance of an IM/FSK combined modulated signal is experimentally validated at 10 Gb/s, demonstrating at the same time an FSK label swapping operation. Finally, a suitable optical label-controlled switch design is proposed that takes advantage of these novel labeling techniques, and efficiently combines widely tunable, fast switching lasers and SOA-MZI wavelength converters with an arrayed waveguide grating router.

Differentiated reliability in optical networks: theoretical and practical results

Abstract: This paper presents both theoretical and experimental studies carried on wavelength-division multiplexing (WDM) networks with arbitrary (mesh) topology that provide optical circuits with differentiated reliability (DiR). Reliability is obtained by means of a modified shared path protection (SPP) switching scheme-here referred to as SPP-DiR. As explained in the paper, SPP-DiR networks provide multiple degrees of circuit reliability that satisfy client-specific reliability requirements in a cost-effective way. The theoretical study first defines the problem of optimally designing SPP-DiR WDM networks. It then presents a time-efficient suboptimal algorithm that determines the routing and the reliability degree of each demand in the given traffic matrix by applying both the conventional SPP and the SPP-DiR scheme. When compared to dedicated path protection switching, results obtained for the pan-European network using the proposed algorithm indicate cost reductions of about 16% when SPP is applied, and up to 34% when SPP-DiR is applied. The experimental study describes the /spl Omega/ testbed-a WDM optical circuit-switched mesh network with an IP control plane-which is believed to be the first testbed ever built that makes use of the SPP-DiR scheme. Experimental results performed on the /spl Omega/ testbed report restoration times of the optical circuits-disrupted by a fiber fault-that are few tens of milliseconds.

High-output-power polarization-insensitive semiconductor optical amplifier

Abstract: A high-output-power 1550 nm polarization-insensitive semiconductor optical amplifier (SOA) was developed for use as a compact in-line optical amplifier. A very thin tensile-strained bulk structure was used for the active layer and active width-tapered spot-size converters (SSCs) were integrated on both input and output sides. The SOA module exhibited a high saturation output power of +17 dBm together with a low noise figure of 7 dB, large gain of 19 dB, and low polarization sensitivity of 0.2 dB for optical signals of 1550 nm wavelength. For the amplification of optical signals modulated at 10 Gb/s in the nonreturn-to-zero (NRZ) format, a good eye pattern without waveform distortion due to the pattern effect was obtained at an average output power of up to +12 dBm. Additionally, good amplification characteristics were demonstrated for the signal wavelength range corresponding to the C-band.

S-band erbium-doped fiber amplifiers with a multistage configuration /sub e/sign, characterization, and gain tilt compensation

Abstract: We report an S-band erbium-doped fiber amplifier (EDFA) with a multistage configuration in terms of its design, gain, and noise characteristics for various pump powers and input signal powers, the temperature dependence of the gain spectra, and gain tilt compensation for changes in input signal power and temperature change. We show that there is a tradeoff between low noise and efficiency in the S-band EDFA and describe the development of an S-band EDFA with a flattened gain of more than 21 dB and a noise figure of less than 6.7 dB. We also show that there is a change in the gain spectra with changes in the pump power and input signal power that is different from that observed in C- and L-band EDFAs, and that our EDFA has a temperature-insensitive wavelength. Furthermore, we develop a gain tilt compensated S-band EDFA that can cope with changes in input signal power and temperature.