Showing papers on "Wavelength-division multiplexing published in 1999"

Optical burst switching (OBS) - a new paradigm for an optical Internet

Abstract: To support bursty traffic on the Internet (and especially WWW) efficiently, optical burst switching (OBS) is proposed as a way to streamline both protocols and hardware in building the future generation Optical Internet. By leveraging the attractive properties of optical communications and at the same time, taking into account its limitations, OBS combines the best of optical circuit-switching and packet/cell switching. In this paper, the general concept of OBS protocols and in particular, those based on Just-Enough-Time (JET), is described, along with the applicability of OBS protocols to IP over WDM. Specific issues such as the use of fiber delay-lines (FDLs) for accommodating processing delay and/or resolving conflicts are also discussed. In addition, the performance of JET-based OBS protocols which use an offset time along with delayed reservation to achieve efficient utilization of both bandwidth and FDLs as well as to support priority-based routing is evaluated.

Erbium-Doped Fiber Amplifiers: Fundamentals and Technology

Abstract: INTRODUCTION 1.1 Long Haul Fiber Networks 1.2 Historical Development of Erbium-Doped Fiber Amplifiers 1.3 From Glass to Systems 2 OPTICAL FIBER FABRICATION 2.1 Introduction 2.2 Conventional Communication Fiber 2.3 Rare Earth Doped Fibers 2.4 Pump-Signal Interaction Methods 2.5 Compositions 2.6 Physical Properties 3 COMPONENTS AND INTEGRATION 3.1 Introduction 3.2 Fiber Connectors 3.3 Fusion Splicing 3.4 Pump and Signal Combiners 3.5 Isolators 3.6 Circulators 3.7 Filters 3.8 Fiber Gratings 3.9 Signal Multiplexers and Demultiplexers 3.10 Signal Add/Drop Components 3.11 Dispersion Compensation Components 3.12 Integrated Components 3.13 Pump Lasers 4 RARE EARTH IONS--INTRODUCTORY SURVEY 4.1 Introduction 4.2 Atomic Physics of the Rare Earths 4.3 Optical Spectra of Rare Earth Ions 4.4 Fundamental Properties 4.5 Spectroscopy of the Er3 Ion 4.6 Er3 -Er3 Interaction Effects 5 ERBIUM-DOPED FIBER AMPLIFIERS--AMPLIFIER BASICS 5.1 Introduction 5.2 Amplification in Three-Level Systems 5.3 Reduction of the Three-Level System to the Two-Level System 5.4 Amplified Spontaneous Emission 5.5 Analytical Solutions to the Two-Level System 6 ERBIUM-DOPED FIBER AMPLIFIERS--MODELING AND COMPLEX EFFECTS 6.1 Introduction 6.2 Absorption and Emission Cross Sections 6.3 Gain and ASE Modeling 6.4 Amplifier Simulations 6.5 Transverse Mode Models--Erbium Confinement Effect 6.6 Excited State Absorption Effects 6.7 Er3 -Er3 Interaction Effects 7 OPTICAL AMPLIFIERS IN FIBER OPTIC COMMUNICATION SYSTEMS--THEORY 7.1 Introduction 7.2 Optical Noise: Device Aspects 7.3 Optical Noise: System Aspects 8 AMPLIFIER CHARACTERIZATION AND DESIGN ISSUES 8.1 Introduction 8.2 Basic Amplifier Measurement Techniques 8.3 Amplifier Design Issues 9 SYSTEM IMPLEMENTATIONS OF AMPLIFIERS 9.1 Introduction 9.2 System Demonstrations and Issues 9.3 Soliton Systems 10 FOUR LEVEL FIBER AMPLIFIERS FOR 13 MM AMPLIFICATION 10.1 Introduction 10.2 Pr3 -doped Fiber Amplifiers 10.3 Nd3 -doped Fiber Amplifiers Appendix Subject Index

Optical Filter Design and Analysis: A Signal Processing Approach

Abstract: From the Publisher: A Unique, Cutting-Edge Approach to Optical Filter Design With more and more information being transmitted over fiber-optic lines, optical filtering has become crucial to the advanced functionality of today’s communications networks. Helping researchers and engineers keep pace with this rapidly evolving technology, this book presents digital processing techniques for optical filter design. This higher-level approach focuses on filter characteristics and enables readers to quickly calculate the filter response as well as tackle larger and more complex filters. The authors incorporate numerous theoretical and experimental results from the literature and discuss applications to a variety of systems—including the new wavelength division multiplexing (WDM) technology, which is fast becoming the preferred method for system upgrade and expansion. Special features of this book include: *The theory underlying various architectures that can approximate any filter function *Filter design techniques applicable to a broad range of materials systems—from silica to fiber to microelectromechanical (MEM) systems *Design examples relevant to filters for WDM systems and planar waveguide devices *250 figures as well as problem sets for use in graduate-level studies

Impact of transmission impairments on the teletraffic performance of wavelength-routed optical networks

Abstract: In a wavelength-routed optical network, a transmitted signal remains in the optical domain over the entire route (lightpath) assigned to it between its source and destination nodes. The optical signal may have to traverse a number of crossconnect switches (XCSs), fiber segments, and optical amplifiers, e.g., erbium-doped fiber amplifiers (EDFAs). Thus, while propagating through the network, the signal may degrade in quality as it encounters crosstalk at the XCSs and also picks up amplified spontaneous emission (ASE) noise at the EDFAs. Since these impairments continue to degrade the signal quality as it progresses toward its destination, the received bit error rate (BER) at the destination node might become unacceptably high. Previous work on the lightpath routing and wavelength assignment (RWA) problem assumed an ideal physical layer and ignored these transmission impairments. The main contribution of our work is to incorporate the role of the physical layer in setting up lightpaths by employing appropriate models of multiwavelength optical devices (XCSs and EDFAs) such that the BER of a candidate lightpath can be computed, in advance, to determine if this lightpath should be used for the call. Features from existing RWA algorithms are integrated with our on-line BER calculation mechanism. Our simulation studies indicate that employing BER-based call-admission algorithms has a significant impact on the performance of realistic networks.

A Survey of Virtual Topology Design Algorithms for Wavelength Routed Optical Networks

Abstract: In the past few years, there has been growing interest in wide area ``All Optical Networks'''' with {\em wavelength division multiplexing\/} (WDM), using {\em wavelength routing}. Due to the huge bandwidth inherent in optical fiber, and the use of WDM to match user and network bandwidths, the wavelength routing architecture is an attractive candidate for future backbone transport networks. A {\em virtual topology\/} over a WDM WAN consists of clear channels between nodes called {\em lightpaths}, with traffic carried from source to destination without electronic switching ``as far as possible'''', but some electronic switching may be performed. Virtual topology design aims at combining the best of optical switching and electronic routing abilities. Designing a virtual topology on a physical network consists of deciding the lightpaths to be set up in terms of their source and destination nodes and wavelength assignment. In this survey we first describe the context and motivations of the virtual topology design problem. We provide a complete formulation of the problem, describe and compare the formulations and theoretical results as well as algorithms, heuristics and some results in the current literature in the field. The reconfigurability issue, which is another attractive characteristic of optical networks, is also discussed and the literature surveyed. This survey is restricted to transport networks with wavelength routing. Similar virtual topology problems also arise in multihop broadcast local area optical networks, but this work does not directly apply to them and corresponding literature is not included in this survey. This survey also relates to the design of a static topology, not one in which individual lightpaths are set up and torn down in response to traffic demand.

Wavelength add-drop switching using tilting micromirrors

Abstract: This paper describes a single-mode optical fiber switch which routes individual signals into and out of a wavelength multiplexed data stream without interrupting the remaining channels. The switch uses free-space optical wavelength multiplexing and a column of micromechanical tilt-mirrors to switch 16 channels at 200 GHz spacing from 1531 to 1556 nm. The electrostatically actuated tilt mirrors use an 80 V peak-to-peak 300 KHz sinusoidal drive signal to switch between /spl plusmn/10/spl deg/ with a 20 /spl mu/s response. The total fiber-to-fiber insertion loss for the packaged switch is 5 dB for the passed signals and 8 dB for added and dropped signals, with 0.2 dB polarization dependence. Switching contrast was 30 dB or more for all 16 channels and all input and output states. We demonstrate operation by switching 622 Mb/s data on eight wavelength channels between the two input and output ports with negligible eye closure.

WASPNET: a wavelength switched packet network

Abstract: WASPNET is an EPSRC-funded collaboration between three British Universities: the University of Strathclyde, Essex University, and Bristol University, supported by a number of industrial institutions. The project which is investigating a novel packet-based optical WDM transport network-involves determining the management, systems, and devices ramifications of a new network control scheme, SCWP, which is flexible and simplifies optical hardware requirements. The principal objective of the project is to understand the advantages and potential of optical packet switching compared to the conventional electronic approach. Several schemes for packet header implementation are described, using subcarrier multiplexing, separate wave lengths, and serial transmission. A novel node design is introduced, based on wavelength router devices, which reduce loss, hence reducing booster amplifier gain and concomitant ASE noise. The fabrication of these devices, and also wavelength converters, are described. A photonic packet switching testbed is detailed which will allow the ideas developed within WASPNET to be tested in practice, permitting the practical problems of their implementation to be determined.

A silicon MEMS optical switch attenuator and its use in lightwave subsystems

Abstract: A single-mode fiber connectorized microelectromechanical systems (MEMS) reflective optical switch attenuator operating in the 1550-nm wavelength region is described The device consists of an electrostatically actuated gold-coated silicon vane interposed in a fiber gap yielding 081-dB minimum insertion loss in the transmit state and high transmission isolation in the reflection state with 215-dB minimum return loss The switch attenuators also work as continuously variable optical attenuators capable of greater than 50-dB dynamic range and can be accurately regulated with a simple feedback control circuit Switching voltages were in the range of 5-40 V and a switching time of 64 /spl mu/s was achieved The MEMS switch can be used in optical subsystems within a wavelength-division-multiplexed (WDM) optical network such as optical power regulators, crossconnects, and add/drop multiplexers We used a discrete array of 16 switch attenuators to implement a reconfigurable 16-channel 100-GHz spacing WDM drop module of an add/drop multiplexer Thru-channel extinction was greater than 40 dB and average insertion loss was 21 dB Both drop-and-transmit of multiple channels (11-18-dB contrast, 14-19-dB insertion loss) and drop-and-detect of single channels (>20-dB adjacent channel rejection, 10-14-dB insertion loss) were demonstrated

100 nm bandwidth flat-gain Raman amplifiers pumped and gain-equalised by 12-wavelength-channel WDM laser diode unit

Abstract: 100 nm bandwidth Raman amplifiers have been realised using a 12-wavelength-channel WDM pumping unit comprising high-power GRINSCH strained layer MQW BH laser diode modules. The gain flatness is less than /spl plusmn/0.5 dB, which is achieved through the asymmetric channel allocation of the pump and without the use of any gain equalisation filters.

Transparent optical packet switching: The European ACTS KEOPS project approach

Abstract: The huge traffic growth which is currently experienced (traffic nearly doubles every year) and foreseen to continue for several years calls for high capacity networks capable of efficiently handling various types of traffic (voice, video, data). WDM (Wavelength Division Multiplexing) optical networks exploiting also fast optical packet switching are expected to provide the required capacity and flexibility for the next generation of high-speed networks. In this context, the European ACTS KEOPS project (KEys to Optical Packet Switching) has concentrated on the definition, development and assessment of optical packet switching and routing networks capable of providing transparency to the payload bit rate. Optical packets of fixed duration have been considered where the payload bit rate, which is user-dependent, can vary from a few hundred Mb/s to 10 Gb/s whereas the header is at a fixed low bit rate (622 Mb/s) to facilitate processing at the network/node interfaces. The challenge addressed by the KEOPS project was therefore to combine the advantages of the relatively coarse-grained WDM techniques with emerging all-optical switching capabilities to yield a high-throughput optical platform directly underpinning next generation data networks (ATM, IP). The project which involved nine partners (Alcatel Alsthom Recherche (F), France Telecom-CNET (F), CSELT (I), Technical University of Denmark (DK), Alcatel CIT (F), Alcatel SEL (D), University of Bologna (I), ETH-Zurich (CH) and University of Strathclyde (UK)) has addressed both network and system studies as well as demonstration experiments based on advanced optoelectronic components developed in the project in order to validate the proposed concept.

Coherent and incoherent crosstalk in WDM optical networks

Abstract: The impact of coherent and incoherent crosstalk on an optical signal passing through optical cross-connect nodes (OXC's) in wavelength division multiplexing (WDM) optical networks is studied, and the analytical expressions are given. Such crosstalk will be generated when the optical propagation delay differences of optical paths in an OXC do not exceed the coherent time of the lasers. While causing fluctuation of signal power, coherent crosstalk may cause noise or not, depending on the relationship between the optical propagation delay differences and the time duration of one bit of the signal. Incoherent crosstalk may cause very high noise power, because it can be a coherent combination of crosstalk contributions. The statistical impact of all crosstalk contributions on signal is studied by simulation, and the concept of quantile is proposed to relax the crosstalk specification requirement for components. The crosstalk specification requirements are then obtained for components used in WDM optical networks with different scales.

Bragg grating fast tunable filter for wavelength division multiplexing

Abstract: A Bragg grating fast tunable filter prototype working over a linear tuning range of 45 nm with a maximum tuning speed of 21 nm/ms has been realized. The tunable filter system is based on two piezoelectric stack actuators moving a mechanical device thus compressing an apodized fiber Bragg grating. The filter allows both traction and compression and can work in transmission and in reflection. It is designed to work with a channel spacing of 100 GHz according to the ITU specifications for wavelength division multiplexing systems.

All-optical label swapping with wavelength conversion for WDM-IP networks with subcarrier multiplexed addressing

Abstract: We report the first demonstration of all-optical label swapping with wavelength conversion and subcarrier multiplexed addressing for WDR IP. This demonstration utilizes a module which is based on cascaded semiconductor optical amplifier wavelength converters that perform the functions of label removal, label rewriting, payload 2R regeneration and double sideband subcarrier label regeneration. Replacement of double-sideband subcarrier labels on a hop-by-hop basis addresses the problem of dispersion induced fading in a multihop fiber network. A direct detection subcarrier receiver is used to recover the label. Switching over four wavelengths covering 16 nn is demonstrated with noninverting wavelength conversion of 2.5-Gb/s payloads and burst mode recovery of 10-Mb/s labels. BER measurements of better than 10/sup -9/ for the wavelength-converted payload and rewritten labels at all wavelengths are presented.

320 Gbit/s (8 × 40 Gbit/s) WDM transmission over 367 km with 120 km repeater spacing using carrier-suppressed return-to-zero format

Abstract: The authors demonstrate +11 dBm-per-channel 320 Gbit/s (8/spl times/ 40 Gbit/s) WDM transmission over a 367 km zero-dispersion-flattened transmission line with 120 km repeater spacing using a nonlinearity-tolerant carrier-suppressed return-to-zero format.

Performance of a time- and wavelength-interleaved photonic sampler for analog-digital conversion

Abstract: We experimentally demonstrate the sampling of microwave signals using a novel time- and wavelength-interleaved pulse train derived from a mode-locked fiber laser. Experimental results are presented indicating a modulator limited bandwidth of 18 GHz and a laser relative intensity noise limited effective number of bits of /spl sim/7 when tested for use in a hybrid photonic analog-digital converter architecture.

Combined WDM and SONET network design

Abstract: This paper considers grooming of low speed traffic into high speed lightpaths in a WDM based optical ring with a primary goal of reducing the cost of the entire system, which is dominated by the cost of the SONET transmission equipment connected to the optical ring. The paper attempts to enumerate the architectural options provided by SONET to arrive at a cost-effective solution, including unidirectional path-switched rings (UPSR) and bidirectional line-switched rings (BLSR), use of back-to-back connections between SONET ADMs to reduce the overall cost, and use of different ring speeds (OC-48 and OC-12). To demonstrate each of the architectures, a uniform traffic is considered and its grooming and resulting SONET architecture demonstrated. The paper deviates from earlier approaches which break the problem into two steps: traffic grooming and assignment of lightpaths to rings, in that it looks at the problem as a whole and tries to solve it in a single step. The paper also considers the characteristics of SONET UPSR and BLSR rings and how these affect the grooming. The paper derives lower and upper bounds to these problems for uniform traffic and shows how these improve on known results.

Quantifying the benefit of wavelength add-drop in WDM rings with distance-independent and dependent traffic

Abstract: One drawback to deploying wavelength division multiplexed (WDM) synchronous optical network (SONET) rings is the potentially large amount of equipment necessary for their deployment. Wavelength add-drop multiplexers potentially reduce the amount of required SONET terminal equipment by allowing individual wavelengths to optically bypass a node rather than being electronically terminated. We have quantified the maximum terminal-equipment savings attainable using wavelength add-drop for rings carrying uniform traffic and rings carrying distance-dependent traffic. The analysis makes use of both an enumerative methodology, and a "super-node" approximation technique that is applicable to arbitrary ring size and internode demand. In both the uniform and distance-dependent traffic scenarios, maximum terminal-equipment savings are shown to rapidly increase, over the region of interest, with both network size and internode demand. The value of wavelength add-drop is accordingly expected to grow rapidly in rings interconnecting numerous high-capacity nodes.

Hierarchical optical path cross-connect systems for large scale WDM networks

Abstract: Hierarchical optical path architecture consisting of wavelength-division multiplexing (WDM) bands and channels are suitable for large-scale WDM backbone networks. A hierarchical optical path crossconnect system (OPXC) using a matrix WDM scheme is proposed as a reliable and economical high-performance node architecture.

Crosstalk due to optical fiber nonlinearities in WDM CATV lightwave systems

Abstract: Crosstalk in a two-wavelength 1550-nm standard fiber system at subcarrier frequencies 50-800 MHz is investigated. The dependence of the crosstalk on subcarrier frequency, wavelength spacing, and optical power is measured and analyzed. The observed crosstalk is attributed to three primary mechanisms: stimulated Raman scattering, cross-phase modulation, and the optical Kerr effect combined with polarization-dependent loss. At wavelength spacing greater than 9 nm, stimulated Raman scattering dominates. At wavelength spacing less than 5 nm, the primary contributor can be the optical Kerr effect with polarization dependent loss, except at higher modulation frequencies where cross-phase modulation also is significant. At even modest (by CATV standards) optical power, the crosstalk is as high as -40 to -45 dB.

Wide-band and gain-flattened hybrid fiber amplifier consisting of an EDFA and a multiwavelength pumped Raman amplifier

Abstract: A wide-band and finely gain-flattened hybrid fiber amplifier is realized. The seamless 3.0-, 1.3-, and 1.0-dB bandwidths of 80, 76, and 69 nm with relative gain-flatness of 11.3%, 4.7%, and 3.7%, respectively, are achieved for the first time using the amplifier. The amplifier consists of an erbium-doped fiber amplifier, which has a short fluoride-based erbium-doped fiber, a discrete Raman amplifier, which has two isolated Raman fibers pumped simultaneously at three wavelengths, and a small-peak-loss gain-equalizer. The amplifier also yields optical noise figures under 6.0 dB.

1.8-THz bandwidth, zero-frequency error, tunable optical comb generator for DWDM applications

Abstract: We report on the experimental realization of a simple optical comb generator, based on phase modulation within an amplified fiber loop, which offers exact referencing to an arbitrary supplied reference frequency and tunable comb-line spacing. At a reference wavelength of 1529 nm up to 103 comb lines within a 40-dB power envelope were generated with spacings adjustable from 1 to 25 GHz, limited only by the bandwidth of the phase modulator.

Introduction to Dwdm Technology: Data in a Rainbow

Abstract: Preface Acknowledgments Introduction FUNDAMENTALS OF LIGHT The Nature of Light Interaction of Light with Matter OPTICAL COMPONENTS The Optical Waveguide: The Fiber Optical Spectral Filters and Gratings Optical Demultiplexers Light Sources Photodetectors Light Amplifiers Other Optical Components Optical Cross-Connects Optical Add-Drop Multiplexers CODING OPTICAL INFORMATION Digital Transmission and Coding Techniques Decoding Optical Information DENSE WAVELENGTH DIVISION MULTIPLEXING DWDM Systems Engineering DWDM Systems DWDM Topologies DWDM CURRENT ISSUES AND RESEARCH State of the Art Acronyms and Abbreviations Answers Index About the Author.

Cross-phase modulation in multispan WDM optical fiber systems

Abstract: The spectral characteristics of cross-phase modulation (XPM) in multispan intensity-modulation direct-detection (IM-DD) optical systems are investigated, both experimentally and theoretically. XPM crosstalk levels and its spectral features are found to be strongly dependent on fiber dispersion and optical signal channel spacing. Interference between XPM-induced crosstalk effects created in different amplified fiber spans is also found to be important to determine the overall frequency response of XPM crosstalk effects. XPM crosstalk between channels with different data rates is evaluated. The crosstalk level between higher and lower bit rate channels is found to be similar to that between two lower bit rate channels. The effect of dispersion compensation on XPM crosstalk in multispan optical systems is discussed and per span dispersion compensation was found to be the most effective way to minimize the effect of XPM crosstalk.

Analysis and design of resilient multifiber wavelength-routed optical transport networks

Abstract: Wavelength-routed optical networks (WRONs) are attracting significant attention for future high-capacity transport applications. This paper studies resilient multifiber WRONs, investigating the influence on the network performance of the maximum number of wavelengths per fiber W restoration strategies, node functionality, and physical topology. Fiber requirements are analyzed for numerous network topologies both without and with link failure restoration, considering different optical cross-connect (OXC) configurations and terminal functionalities. An integer linear program (ILP) formulation is presented for the exact solution of the routing and wavelength allocation (RWA) problem, with minimal total number of fibers, F/sub T/(W). Lower bounds on F/sub T/(W) are discussed, and heuristic algorithms proposed. Three restoration strategies are considered and compared in terms of capacity requirement. Different network topologies are analyzed, to evaluate the influence of physical connectivity and network size on the restoration capacity. Network evolution in terms of growth in traffic demand is investigated to study the importance of wavelength conversion within the OXC's as a function of network size and connectivity, traffic demand, and wavelength multiplicity W.

100 nm bandwidth flat gain Raman amplifiers pumped and gain-equalized by 12-wavelength-channel WDM high power laser diodes

Abstract: We demonstrate 100 nm bandwidth Raman amplifiers using 12-wavelength-channel WDM pump laser diode unit. The gain flatness is less than /spl plusmn/0.5 dB, which is achieved through an asymmetric channel allocation of pump and without any gain equalization filters.

Non-intrusive fiber optic pressure sensor for measuring unsteady pressures within a pipe

Abstract: Non-intrusive pressure sensors (14-18) for measuring unsteady pressures within a pipe (12) include an optical fiber (10) wrapped in coils (20-24) around the circumference of the pipe (12). The length or change in the length of the coils (20-24) is indicative of the unsteady pressure in the pipe. Bragg gratings (310-324) impressed in the fiber (10) may be used having reflection wavelength μ that relate to the unsteady pressure in the pipe. One or more of sensors (14-18) may be axially distributed along the fiber (10) using wavelength division multiplexing and/or time division multiplexing.

Apparatus and method for controlling power levels of individual signal lights of a wavelength division multiplexed signal light

Abstract: An apparatus and method for controlling power levels of individual signal lights of a wavelength division multiplexed (WDM) signal light. The apparatus includes an optical fiber, a coupler and a controller. The WDM signal light travels through the optical fiber. The WDM signal light includes a plurality of individual signal lights which each have a corresponding power level. The coupler decouples a portion of the WDM signal light from the optical fiber. The controller determines the spectrum of the WDM signal light from the decoupled portion and controls the power levels of the plurality of individual signal lights in accordance with the determined spectrum. More specifically, the controller can control the relative power levels of the plurality of individual signal lights with respect to each other. In addition, the controller can control the power levels of the plurality of individual signal lights to perform preemphasis on the WDM signal light. The controller can control the power levels of the plurality of individual signal lights to obtain substantially equal signal to noise ratios of the plurality of individual signal lights as received by a receiver through the optical fiber. The method includes the steps of (a) decoupling a portion of a WDM signal light travelling through an optical fiber (b) determining the spectrum of the WDM signal light from the decoupled portion, and (c) controlling the power levels of individual signal lights of the WDM signal light in accordance with the determined spectrum.

Fiber laser hydrophone array

Abstract: In recent years growing interest has surrounded the development of fiber laser sensors (FLS). This is due to their ultra high sensitivity to temperature and strain as well as their ability to be multiplexed along a single fiber using WDM techniques. It is their extreme sensitivity that has led to them being considered as acoustic pressure sensors rather than standard fiber Bragg gratings. The work presented here describes the development of an array of FLS configured as hydrophones. We discuss the design of the single mode fiber laser used throughout our system; comparing examples based upon distributed Bragg reflectors (DBR) and distributed feedback (DFB). In addition we discuss both the theoretical and experimental acoustic sensitivity enhancements obtained by the application of an elasto-plastic coating to the FLS. The array configuration is described, as is the heterodyne interrogation scheme using an unbalanced Mach-Zehnder interferometer with WDM channel selection. Results from the measurement of the minimal detectable acoustic signal of a bare fiber laser are shown to be -69 dB re.Pa/(root)Hz at 1 kHz when using a 200 m path imbalanced readout interferometer. Further gains in the sensitivity due to the application of various coatings are reported, as is a full characterization of an array of fiber laser hydrophones. Finally we discuss the future research of the FLS, and the areas in which the technology is particularly applicable.

Optical fiber amplifiers for WDM optical networks

Abstract: In recent years, tremendous progress has been made in the development of broadband erbium-doped fiber amplifiers (EDFAs), which form the backbone of high-capacity lighwave communication systems. Initially, the use of gain equalization filters increased the bandwidth of amplifiers by a factor of three (relative to first-generation amplifiers deployed in the field). Subsequently, the introduction of a two-band architecture, which includes amplifier sections for the C-band and the L-band, resulted in a further doubling of the bandwidth. In addition, this amplifier provides high output power and low noise figure to support the ever-increasing capacity demand on lightwave systems. Commercial systems with up to 80 wavelength division multiplexing (WDM) channels having a total capacity of up to 400 Gb/s are currently available, and terabit systems have been demonstrated in the laboratory. The recently discovered phenomenon of fast power transients in chains of EDFAs constituting an optical network has been shown to impair the performance of propagating channels in the event of channel failure or network reconfiguration. Several schemes to control the gain of EDFAs have been devised to mitigate the degradation caused by the fast power transient effect. Practical broadband amplifiers incorporating these and other control schemes, such as internal attenuation to control gain tilt, will enable future terabit and higher capacity networks.

Surface micromachined fabry-perot tunable filter

Abstract: We report the fabrication of a wavelength tunable optical filter using surface micromachining technology. The center wavelength is 1.517 /spl mu/m and the transmission bandwidth is 5 nm. The device with a 50-/spl mu/m diameter aperture has an optical loss of about 5 dB. A continuous wavelength tuning of 60 nm has been demonstrated. This device may find applications in optical sensing and wavelength division multiplexing systems, and can be readily integrated with surface emitting lasers, modulators, and detectors.