Showing papers on "Wavelength-division multiplexing published in 2001"

Techniques for optical packet switching and optical burst switching

Abstract: Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Several different technologies have been developed so far for the transfer of data over WDM. We survey two new technologies which are still in the experimental stage-optical packet switching and optical burst switching-and comment on their suitability for transporting IP traffic.

Ultrabroad-band Raman amplifiers pumped and gain-equalized by wavelength-division-multiplexed high-power laser diodes

Abstract: This paper reviews recent progress in broad-band Raman amplifiers for wavelength-division-multiplexed (WDM) applications. After the fundamentals of Raman amplifiers are discussed in contrast to erbium-doped fiber amplifiers, a new technique called "WDM pumping" is introduced to obtain ultrabroad and flat gain in Raman amplifiers only using WDM diode pumps. The design issues of this technique are then developed to realize outstanding performances such as 100 nm of flat gain bandwidth, 0.1 dB flatness over 80 nm, and so forth.

Single side-band modulation performance of a LiNbO 3 integrated modulator consisting of four-phase modulator waveguides

Abstract: Single side-band (SSB) technologies are especially useful in optical fiber communication systems, such as higher density wavelength multiplexing and long-haul fiber transmission due to less nonlinear optical effects, because of the reduced optical power. This letter reports on the SSB modulation performance of a LiNbO/sub 3/ integrated modulator consisting of four phase modulator waveguides. Optical SSB modulation with suppressions of main carrier (-22.6 dB) and J/sub 3/ subcarrier (-18.4 dB) of a 10-GHz single-tone signal with a driving voltage of 6.3 V/sub p-p/ was demonstrated. The total insertion loss was 10.6 dB.

Optical burst switching for service differentiation in the next-generation optical Internet

Abstract: In an effort to eliminate the electronic bottleneck, new optical switches/routers (hardware) are being built for the next-generation optical Internet where IP runs over an all-optical WDM layer. However, important issues yet to be addressed in terms of protocols (software) are how to develop a new paradigm that does not require any buffer at the WDM layer, as in circuit switching, and elimination of any layers between which exist mainly due to historical reasons. At the same time, such a paradigm should also efficiently support bursty traffic with high resource utilization as in packet switching. This article surveys design issues related to a new switching paradigm called optical burst switching, which achieves a balance between circuit and packet switching while avoiding their shortcomings. We describe how OBS can be applied to the next-generation optical Internet, and in particular how offset times and delayed reservation can help avoid the use of buffer, and support quality of service at the WDM layer.

Spectral slicing WDM-PON using wavelength-seeded reflective SOAs

Abstract: A method of implementing wavelength division multiplexed-passive optical network (WDM-PON) upstream channels based on spectral slicing with wavelength-seeded travelling-wave reflective semiconductor optical amplifier (SOA) modulators is described. A dense WDM comprising eight 1 nm slices, each modulated at a data rate of 1.25 Gbit/s are shown to operate over 25 km of standard fibre with negligible crosstalk and <1 dB dispersion penalty.

Multiwavelength fiber laser sources with Bragg-grating sensor multiplexing capability

Abstract: Two erbium-doped fiber ring lasers (EDFRLs) wvith simultaneous emission at four different wavelengths are demonstrated. Both systems employ fiber Bragg gratings (FBGs) to select the operation wavelengths within the ring. The sensing capability of the FBGs has been taken advantage of, allowing for the sources to be used as sensor multiplexing schemes. The first system employs four FBGs in a tree filter topology, achieving four output channels with -5 dBm power each. The second system comprises an in-line filtering topology with active fiber segments within the filter. This second source yields 2-dBm output signals and allows for a higher number of lines to be easily added to the system. A comparison between both topologies is carried out, and their capability for sensor multiplexing is demonstrated.

OSNR monitoring technique using polarization-nulling method

Abstract: We report on the simple technique for monitoring the optical signal-to-noise ratios (OSNRs) of wavelength-division-multiplexed (WDM) signals. This technique, based on the polarization-nulling method, was implemented simply by using a rotating quarter-wave plate and rotating linear polarizer. However, the performance of this technique could be affected by nonlinear birefringence and polarization-mode dispersion (PMD). The result shows that this technique is suitable for monitoring the OSNRs of highspeed (>10-Gb/s) WDM signals transported over the fiber link with low PMD.

10.92-Tb/s (273/spl times/40-Gb/s) triple-band/ultra-dense WDM optical-repeatered transmission experiment

Abstract: With LD-pumped gain-shifted thulium-doped fiber amplifiers, polarization interleave multiplexing combined with wavelength/polarization demultiplexing for 50-GHz-spaced 40-Gb/s/ch WDM signals, and a transmission line optimization for triple-band systems, the first 10-Tb/s WDM transmission in single fiber using S-, C- and L-bands is demonstrated.

Progress in optical networking

Abstract: This article summarizes the present state of optical networking, how we got to this point, and what needs to be done to complete the job. The point of departure is an assumed future two-level structure in which the transport is by means of steadily growing interconnected all-optical islands of transparency, while the remainder of the communication layers are based on IP, both levels being managed by an MPLS-based control plane. After reviewing why such networks are becoming inevitable, a review is given of the various optical layer technology and architecture bottlenecks that have had to be solved. Issues that remain center on increasing the number of channels and reducing the technology costs.

Widely tunable erbium-doped fiber ring laser covering both C-band and L-band

Abstract: We demonstrate a widely tunable erbium-doped fiber (EDF) ring laser covering both the conventional wavelength band (C-band) and the long wavelength band (L-band). It features a wide tunable range, high output power, low-coherent, and depolarized output. A tunable range over 80 nm (1520-1600 nm) has been achieved by optimizing the length of the EDF and by using an intracavity fiber Fabry-Perot (FFP) filter.

Multiplexed optical scanner technology

Abstract: High speed optical scanner systems and methods using optical multiplexing of wavelengths and spatial codes. In one form, a wavelength multiplexed optical scanner (W-MOS) is disclosed, wherein tuning the wavelength or selection of wavelength accomplishes a high speed, no-moving, parts scanner coupled with a wavelength dispersive element, such as a grating or a thin-film interference filter. In another form, a W-MOS employs beam expansion optics and a freespace-coupled wavelength dispersive element. In another embodiment, the invention includes a fiber-based W-MOS using an optical fiber coupled with a fiber-based wavelength division multiplexer (WDM) device to form a spatially distributed scanner for wide angular coverage in three-dimensional beam scanning. The invention also includes a code multiplexed optical scanner (C-MOS) that uses the principle of holography and spatial code multiple access optical communications. In addition, an optical wireless application is disclosed using the C-MOS's to give fault-tolerance to an indoor wireless network.

Wavelength division multiplexing optical communication system and wavelength division multiplexing optical communication method

Abstract: The object of the present invention is to provide a WDM optical communication system and a WDM communication method wherein deviation of transmission characteristics of optical signals of respective wavelengths is reliably controlled, based on reception information such as the OSNR, BER and the like measured at the receiving end, thereby enabling optimal transmission conditions to be realized. For this purpose, the present WDM optical communication system transmits WDM signal light of wavelengths λ1˜λn, which has been generated by the transmitting end of one terminal station, to the receiving end of the other terminal station through an optical transmission path. At the receiving end, the OSNR and BER of the optical signals of wavelengths λ1˜λn are measured, and the result is superimposed on overhead information transmitted along the opposing line of the optical transmission path as reception information. At the transmitting end, the settings of pre-emphasis and a parameter α are feedback controlled based on the reception information about each wavelength transmitted, and deviation of transmission characteristics of respective wavelengths is thus suppressed.

Nonlinear gain dynamics in quantum-dot optical amplifiers and its application to optical communication devices

Abstract: Ultrafast gain dynamics in quantum-dot (QD) optical amplifiers has been studied. It was found that there are at least three nonlinear processes, which are attributed to carrier relaxation to the ground states, phonon scattering, and carrier capture from the wetting layers into the QDs. The relevant time constants were evaluated to be /spl sim/90 fs, /spl sim/260 fs, and /spl sim/3 ps, respectively, under a 50-mA bias condition. The dephasing time was evaluated to be /spl sim/85 fs. The third-order optical susceptibility (/spl chi//sup (3)/) has been evaluated by means of both nonlinear transmission and four-wave mixing experiments. The results show that the nonlinearity expressed by /spl chi//sup (3)//g/sub 0/ is quite similar to that of bulk and quantum wells, which can be explained by similar relaxation times. Applications to optical communication devices are also discussed.

Impact of intermediate traffic grouping on the dimensioning of multi-granularity optical networks

Abstract: We demonstrate the interest of multi-granularity optical networks to decrease the number of ports for the optical switching matrices by grouping some wavelengths into bands and some bands into fibers at some intermediate nodes.

Large-scale multiplexing of interferometric fiber-optic sensors using TDM and DWDM

Abstract: This paper describes multiplexing schemes for interferometric fiber sensors based on time-division multiplexed and dense wavelength-division multiplexing using optical add/drop multiplexers. The results of an experimental arrangement, which is based on one of the architectures, is also presented. Topics include a discussion of the noise sources in the system, dynamic range, and a characterization of the distributed feedback fiber laser source noise. We show the crosstalk levels in the experimental arrangement to be between -47 and -76 dB depending on the mechanism involved. The multiplexing schemes demonstrate the potential to address at least 192 interferometric sensors through two fibers based on a system with six wavelengths with a phase resolution less than 20 /spl mu/rad//spl radic/Hz. For application to sonar arrays, our analysis has shown that hydrophones multiplexed in this type of architecture would achieve ambient acoustic noise-limited pressure resolution with an in-water dynamic range up to 135 dB at frequencies up to 10 kHz. In general, these architectures would find application in systems requiring very large numbers of sensors with a minimum of telemetry cabling required.

Low loss and high extinction ratio strictly nonblocking 16/spl times/16 thermooptic matrix switch on 6-in wafer using silica-based planar lightwave circuit technology

Abstract: We describe a silica-based 16/spl times/16 strictly nonblocking thermooptic matrix switch with a low loss and a high extinction ratio. This matrix switch, which employs a double Mach-Zehnder interferometer (MZI) switching unit and a matrix arrangement to reduce the total waveguide length, is fabricated with 0.75% refractive index difference waveguides on a 6-in silicon wafer using silica-based planar lightwave circuit (PLC) technology. We obtained an average insertion loss of 6.6 dB and an average extinction ratio of 53 dB in the worst polarization case. The operating wavelength bandwidth completely covers the gain band of practical erbium-doped fiber amplifiers (EDFAs). The total power consumption needed for operation is reduced to 17 W by employing a phase-trimming technique which eliminates the phase-error in the interferometer switching unit.

Optimization of wavelength assignment for QoS multicast in WDM networks

Abstract: This paper discusses quality-of-service (QoS) multicast in wavelength-division multiplexing (WDM) networks. Given a set of QoS multicast requests, we are to find a set of cost suboptimal QoS routing trees and assign wavelengths to them. The objective is to minimize the number of wavelengths in the system. This is a challenging issue. It involves not only optimal QoS multicast routing, but also optimal wavelength assignment. Existing methods consider channel setup in WDM networks in two separate steps: routing and wavelength assignment, which has limited power in minimizing the number of wavelengths. In this paper, we propose a new optimization method, which integrates routing and wavelength assignment in optimization of wavelengths. Two optimization algorithms are also proposed in minimizing the number of wavelengths. One algorithm minimizes the number of wavelengths through reducing the maximal link load in the system; while the other does it by trying to free out the least used wavelengths. Simulation results demonstrate that the proposed algorithms can produce suboptimal QoS routing trees and substantially save the number of wavelengths.

Increasing data throughput in optical fiber transmission systems

Abstract: Data throughput rates are increased in an optical fiber communication system without requiring replacement of the existing optical fiber in a link. Channel throughput is increased by upgrading the components and circuitry in the head and terminal of an optical fiber communication system link. Aggregate throughput in a fiber optic link is increased beyond the range of conventional Wavelength Division Multiplexed (WDM) upgrades, while precluding the necessity of replacing existing fiber plants. The increase in system throughput is achieved by using advanced modulation techniques to encode greater amounts of data into the transmitted spectrum of a channel, thereby increasing the spectral efficiency of each channel. This novel method of increasing transmission capacity by upgrading the head and terminal of the system to achieve greater spectral efficiency and hence throughput, alleviates the need to replace existing fiber plants. Spectrally efficient complex modulation techniques can be supported by interface circuits with an increased level of signal processing capability in order to both encode multiple bits into a transmitted symbol and decode the original data from the received symbols.

Real-time location of multiple time-varying strain disturbances, acting over a 40-km fiber section, using a novel dual-Sagnac interferometer

Abstract: Updated results using a novel sensing architecture based on a Sagnac interferometer are presented and, for the first time, real-time separation and positioning of multiple disturbances has been realized. A 40-km long dual-Sagnac sensor was formed by spectral slicing of light from a single, broad-band erbium-doped-fiber super-luminescent source and wavelength division multiplexed (WDM) routing around the loop to form an inherently low loss system. Independent active phase biasing of each Sagnac was employed, allowing the use of a single optical detector. The effects of residual optical cross talk between the two Sagnacs has been accurately modeled, allowing resulting errors to be corrected. The new system has capability for narrow-band fast Fourier transform (FFT) analysis of detected disturbance signals, and hence their separation in the frequency domain. For audio-frequency excitation, an average positional resolution of 100 m over a 40-km length was achieved with a postdetection signal processing bandwidth of 8 Hz.

On the optimization of hybrid Raman/erbium-doped fiber amplifiers

Abstract: A comprehensive theoretical study on the optimal configuration of hybrid Raman/erbium-doped fiber amplifiers has been carried out yielding a closed form analysis. In order to compare different system configurations, a weight for the impact of fiber nonlinearities has been introduced. The maximum reachable distance has been evaluated as a function of the span length and nonlinear weight, given a target optical signal-to-noise ratio.

1296-port MEMS transparent optical crossconnect with 2.07 petabit/s switch capacity

Abstract: A 1296-port MEMS transparent optical crossconnect with 5.1dB/spl plusmn/1.1dB insertion loss at 1550 nm is reported. Measured worst-case optical crosstalk in a fabric was n38 dB and nominal switching rise/fall times were 5 ms. A 2.07 petabit/s switch capacity was verified upon cross-connecting a forty-channel by 40 Gb/s DWDM data stream through a prototype fabric.

The Shannon channel capacity of dispersion-free nonlinear optical fiber transmission

Abstract: We extend the Shannon information theory to a nonlinear system and present a model for calculating the channel capacity of an optical-fiber transmission system using dispersion-free fiber. For this particular fiber, a closed-form solution for the nonlinear Schroedinger equation exists. This allows us to derive an analytical result for the channel capacity that is exact and valid for arbitrary input power. We will study the single-span case and examine the dependence of the capacity on operating input power, the number of channels (N/sub c/), the noise power (P/sub W/), etc. The maximum capacity is shown to follow a simple scaling law with log/sub 2/(1+CN/sub c//sup -2/3/P/sub W//sup -2/3/) dependence, multiplexing (WDM) systems.

Optical packet routing in IP-over-WDM networks deploying two-level optical labeling

Abstract: Assigning a wavelength label as well as a label in a DPSK modulation format orthogonal to the data payload significantly increases the forwarding and routing capabilities of optical packet routers in IP-over-WDM networks.

10.2 Tbit/s (256x42.7 Gbit/s PDM/WDM) transmission over 100 km TeraLight/sup TM/ fiber with 1.28 bit/s/Hz spectral efficiency

Abstract: We demonstrate the transmission of 256 polarization-division and wavelength-division multiplexed channels at 42.7 Gbit/s rate over 100 km of TeraLight/sup TM/ fiber. An overall capacity of 10 Tbit/s is achieved in C and L bands at a record 1.28 bit/s/Hz spectral efficiency.

Fiber-laser-based wavelength-division multiplexed fiber Bragg grating sensor system

Abstract: A wavelength-division-multiplexing technique for interrogating 10-cascaded fiber Bragg grating sensing elements based on a ring-compounded-cavity fiber laser is reported. A feedback control technique was introduced to a tunable Fabry-Perot filter that tracks the wavelength-shift of the sensor. The sensors were demodulated using an unbalanced scanning Michelson interferometer and a sensitivity of 1.682/spl deg///spl mu//spl epsi/ has been demonstrated.

Time and frequency domain characteristics of polarization-mode dispersion emulators

Abstract: We investigate both experimentally and theoretically a new technique to realistically emulate polarization-mode dispersion (PMD). We propose and demonstrate a PMD emulator using rotatable connectors between sections of polarization-maintaining fibers that generates an ensemble of high PMD fiber realizations by randomly rotating the connectors. It is shown that: (1) the DGD of this emulator is Maxwellian-distributed over an ensemble of fiber realizations at any fixed optical frequency; and (2) the frequency autocorrelation function of the PMD emulator resembles that in a real fiber when averaged over an ensemble of fiber realizations. A realistic autocorrelation function is required for proper emulation of higher order PMD and indicates the feasibility of using this emulator for wavelength-division-multiplexing (WDM) systems.

System and method for collimating and redirecting beams in a fiber optic system

Abstract: A connector to an optical fiber comprises a prism, a ferrule and an aspheric lens. The prism includes a triangular wedge element having a first surface, a second surface and a base. The ferrule guides the optical fiber so as to contact the optical fiber with the first surface of the prism. The aspheric lens is integrated on the second surface, the integrated aspheric lens being positioned so that the prism serves to redirect a light beam at an angle relative to an axis of the optical source input through total internal reflection by utilizing the base of the triangle wedge element. The aspheric lens serves to collimate the redirected light beam or focus the light beam before being redirected. This arrangement may, for example, be used within a WDM system to multiplex and de-multiplex several wavelengths of light, using a “zig-zag” optical path configuration and thin film filters to separate the wavelengths.

Observation of PMD-induced coherent crosstalk in polarization-multiplexed transmission

Abstract: We report wavelength-division-multiplexed (WDM) systems experiments with polarization multiplexing at 40 Gb/s per channel and 0.8 bit/s/Hz spectral efficiency designed to explore the worst case impairments caused by first-order polarization-mode dispersion (PMD) in the fiber. Both polarization-division multiplexing using two polarizations at each wavelength and polarization interleaving where adjacent channels have orthogonal polarizations were examined. Measured system penalties show that polarization multiplexing increases the PMD sensitivity by approximately a factor of five due to coherent crosstalk.

DWDM fundamentals, components, and applications

Abstract: Introduction. Basic Principles and Background-Wavelength Division Multiplexing: Basic Principles. History of Wavelength Division Multiplexing in a Few Words. Wavelength Division Multiplexing and Time Division Multiplex. Wavelength Domain and Separation Between Channels. Wavelength Allocation, ITU Grid. Optical Wavelength/Optical Frequency Conversion. How Many Channels? Some Definitions. Solitons. Dense Wavelength Division Multipliers and Demultiplexers-Passive Components, the Current Choices Available. Arrayed Waveguide Gratings. Fiber Bragg Gratings. Optical Multidielectric Filters. Diffraction Gratings. Cascaded Mach-Zehnder Interferometers. Other Devices. Methods for Broadening and Flattening the Spectral Shape of the Transmission Channels of Grating Wavelength Division Multiplexers. Sources and Wavelength Converters for DWDM-Introduction. Semiconductor Lasers. Glass-Doped Based Lasers with Narrow-Linewidths. Spectral Slicing of Sources. Wavelength Converters. Wavelength Division Multiplexing and Optical Amplification-Introduction. Semiconductor Optical Amplifiers (SOA). Brillouin Scattering Amplifiers. Raman Amplifier. Rare Earth-Doped Fiber Optic Amplifiers. Hybrid Raman/Erbium Doped Fiber Amplifiers. Erbium Doped Planar Waveguides. Routers, Cross Connects and Add/Drops-Introduction. Wavelength Conversion. Network Architecture Classification. Some Definitions Used for Interconnection Performance Characterization. Interoperability in Optical Routed DWDM Networks. Space Switches. Passive Wavelength Router(PWR). Optical Cross Connector (OXC). Optical Add/Drop Multiplexers. WDM Limits Caused by Optical Nonlinearities in Optical Fibers-Introduction. Self Phase Modulation (SPM). Cross Phase Modulation(XPM). Four Wave Mixing (FWM). Stimulated Brillouin Scattering (SBS). Stimulated Raman Scattering (SRS). Conclusions. Additional Note. Some Applications of Dense Wavelength Division Multiplexing-Some of the Earlier Applications. Today s DWDM Networks. Long Distance Transmission. Other Applications. Conclusions

Automatic design scheme for optical-fiber Raman amplifiers backward-pumped with multiple laser diode pumps

Abstract: A simulated annealing algorithm is adopted to give an automatic pump configuration in laser-diode backward-pumped-distributed fiber Raman amplifiers. The demonstration of the optimization process of wavelengths and powers in an optical-fiber Raman amplifier using four laser-diode pumps is presented. The resulting gain ripple is less than 2.6 dB in respect to the 30 dB average gain in the amplification bandwidth of more than 50 nm (64 signal channels). The algorithm can be practically applied to the desired signal channel number and gain profile.