Showing papers on "Wavelength-division multiplexing published in 1992"

Fiber-Optic Communication Systems

Abstract: Preface. 1 Introduction. 1.1 Historical Perspective. 1.2 Basic Concepts. 1.3 Optical Communication Systems. 1.4 Lightwave System Components. Problems. References. 2 Optical Fibers. 2.1 Geometrical-Optics Description. 2.2 Wave Propagation. 2.3 Dispersion in Single-Mode Fibers. 2.4 Dispersion-Induced Limitations. 2.5 Fiber Losses. 2.6 Nonlinear Optical Effects. 2.7 Fiber Design and Fabrication. Problems. References. 3 Optical Transmitters. 3.1 Semiconductor Laser Physics. 3.2 Single-Mode Semiconductor Lasers. 3.3 Laser Characteristics. 3.4 Optical Signal Generation. 3.5 Light-Emitting Diodes. 3.6 Transmitter Design. Problems. References. 4 Optical Receivers. 4.1 Basic Concepts. 4.2 Common Photodetectors. 4.3 Receiver Design. 4.4 Receiver Noise. 4.5 Coherent Detection. 4.6 Receiver Sensitivity. 4.7 Sensitivity Degradation. 4.8 Receiver Performance. Problems. References. 5 Lightwave Systems. 5.1 System Architectures. 5.2 Design Guidelines. 5.3 Long-Haul Systems. 5.4 Sources of Power Penalty. 5.5 Forward Error Correction. 5.6 Computer-Aided Design. Problems. References. 6 Multichannel Systems. 6.1 WDM Lightwave Systems. 6.2 WDM Components. 6.3 System Performance Issues. 6.4 Time-Division Multiplexing. 6.5 Subcarrier Multiplexing. 6.6 Code-Division Multiplexing. Problems. References. 7 Loss Management. 7.1 Compensation of Fiber Losses. 7.2 Erbium-Doped Fiber Amplifiers. 7.3 Raman Amplifiers. 7.4 Optical Signal-To-Noise Ratio. 7.5 Electrical Signal-To-Noise Ratio. 7.6 Receiver Sensitivity and Q Factor. 7.7 Role of Dispersive and Nonlinear Effects. 7.8 Periodically Amplified Lightwave Systems. Problems. References. 8 Dispersion Management. 8.1 Dispersion Problem and Its Solution. 8.2 Dispersion-Compensating Fibers. 8.3 Fiber Bragg Gratings. 8.4 Dispersion-Equalizing Filters. 8.5 Optical Phase Conjugation. 8.6 Channels at High Bit Rates. 8.7 Electronic Dispersion Compensation. Problems. References. 9 Control of Nonlinear Effects. 9.1 Impact of Fiber Nonlinearity. 9.2 Solitons in Optical Fibers. 9.3 Dispersion-Managed Solitons. 9.4 Pseudo-linear Lightwave Systems. 9.5 Control of Intrachannel Nonlinear Effects. Problems. References. 10 Advanced Lightwave Systems. 10.1 Advanced Modulation Formats. 10.2 Demodulation Schemes. 10.3 Shot Noise and Bit-Error Rate. 10.4 Sensitivity Degradation Mechanisms. 10.5 Impact of Nonlinear Effects. 10.6 Recent Progress. 10.7 Ultimate Channel Capacity. Problems. References. 11 Optical Signal Processing. 11.1 Nonlinear Techniques and Devices. 11.2 All-Optical Flip-Flops. 11.3 Wavelength Converters. 11.4 Ultrafast Optical Switching. 11.5 Optical Regenerators. Problems. References. A System of Units. B Acronyms. C General Formula for Pulse Broadening. D Software Package.

Lightpath communications: an approach to high bandwidth optical WAN's

Abstract: An architectural approach that meets high bandwidth requirements by introducing a communication architecture based on lightpaths, optical transmission paths in the network, is introduced. Since lightpaths form the building block of the proposed architecture, its performance hinges on their efficient establishment and management. It is shown that although the problem of optimally establishing lightpaths is NP-complete, simple heuristics provide near optimal substitutes for several of the basic problems motivated by a lightpath-based architecture. >

Wavelength division multiple access channel hypercube processor interconnection

Abstract: A hypercube-based structure in which optical multiple access channels span the dimensional axes is introduced. This severely reduces the required degree, since only one I/O port is required per dimension. However, good performance is maintained through the high-capacity characteristics of optical communication. The reduction in degree is shown to have significant system complexity implications. Four star-coupled configurations are studied as the basis for the optical multiple access channels, three of which exhibit the optical self-routing characteristic. A performance analysis shows that through the integration of agile sources or receivers, and wavelength division multiple access, systems can be developed with significant increases in performance yet at a reduction in communication subsystem complexity. >

Transient Bragg reflection gratings in erbium-doped fiber amplifiers.

Abstract: A transient tunable Bragg reflection grating has been established in an erbium-doped fiber amplifier by the effect of a standing wave produced by counterpropagating cw light. Less than 1 mW of cw light was required to establish a grating with a 75% reflection coefficient at 1536 nm and an optical bandwidth (FWHM) of 16 MHz. Possible applications include dispersion compensation and dense wavelength-division multiplexing.

Multiplexing fiber Bragg grating sensors

Abstract: Bragg reflection gratings and out-coupling taps for sensors can be written holographically within the core of many commercial fibers available today. The gratings appear to be permanent and have been tested to temperatures in excess of 500 degree(s)C. Quasi-distributed temperature, strain, pressure, chemical, and interferometric type sensors can be made with the wavelength selective, reflection gratings, and taps. The fiber gratings, and the different types of sensors they can make, conveniently lend themselves to WDM, TDM, and FDM types of multiplexing schemes. Instrumentation to detect the multiple sensors and measure their spectral shift for localized and quasi-distributed sensing is currently under development.

A self-routing WDM high-capacity SONET ring network

Abstract: A dynamic control mechanism, based on subcarrier-multiplexed pilot-tones and acoustooptic tunable filters, is proposed for wavelength routing in a high-capacity wavelength division multiplexed (WDM) SONET interoffice ring network. The authors experimentally verified the network concept and discussed different network applications for bursty data traffic and continuous voice/video traffic. >

A time-wavelength assignment algorithm for a WDM star network

Abstract: The first time-wavelength assignment algorithm for wavelength division multiplexing (WDM) star-based local and metropolitan area networks is presented. The algorithm incorporates the unique aspects of WDM communication such as a number of tunable transmitters and receivers at each concentrator, the tuning time, and a limited number of wavelengths. The transmission duration is composed of two elements: the packet transmission time, and the overhead incurred due to the tunability of the system's transmitters and receivers. For a given traffic matrix, the algorithm obtains a TDM/WDM schedule with minimal packet transmission duration, while minimizing the tuning time. >

Multiple wavelength operation of an erbium-doped fiber laser

Abstract: Wavelength-locked, six-channel, colasing operation using a single gain medium is reported for the first time. The system is an all-fiber, erbium-amplifier-based design that uses a grating wavelength division multiplexer with a fixed channel spacing of 4.8 nm for frequency selection. The authors investigate two possible configurations for the laser cavity. >

Hybrid electronic fiber optic wavelength-multiplexed system for true time-delay steering of phased array antennas

Abstract: A hybrid electronic fiber optic true time-delay steering architecture is presented which retains the highly hardware compressive property of an earlier all-optical approach and introduces the economical advantages of electronics at every level possible without compromising overall performance. The architecture is particularly suited to large arrays where maximum advantage can be taken of the hardware compression. A detailed design based on this architecture is described for steering a linear, 16-element, L -band (0.7- to 1.4-GHz) array in transmit mode over a scan angle of ±20 deg with a delay resolution of 6 bits (0.63 deg). An analysis of the expected performance of the design is given together with progress toward the fabrication of the prototype system, which includes the first iteration electronic binary delay line subsystem and a single-segment, high-fidelity, directly modulated DFB laser diode fiber optic link. The experimental data from these modules is in agreement with the performance predicted from the analysis.

Optical signal equalizer for wavelength division multiplexed optical fiber systems

Abstract: This invention disclosure describes the application of a polarization insensitive acoustically-tuned optical filter used in a multichannel WDM system to equalize variations in the power level of the WDM channels. The invention also describes a simple means for providing a low frequency control system which enables the equalizer to determine the signal levels of N optical carriers prior to equalizing the signals.

Monolithically integrated wavelength division multiplexing laser array

Abstract: An active monolithic optical device for wavelength division multiplexing (WDM) incorporating diode laser arrays, an output coupling waveguide and a curved Rowland circle based grating to produce a plurality of individual laser beams at slightly different wavelengths is integrated in a common electro-optic material. The wavelength of each laser source is determined by the geometry of the array and the diffraction grating design. The output of all the channels can be collected into a concentrator or lens to be multiplexed in a single output. Applications include a WDM optical amplifier and WDM laser source.

A full transparent fiber-optic ring architecture for WDM networks

Abstract: A fully transparent fiber-optic ring architecture for wavelength division multiplexed (WDM) networks is proposed. The physical topology of the proposed network is based on a single or multifiber ring. The nodes at the periphery of the network are connected onto the ring via a polarization-independent acoustically tunable optical filter (PIATOF). This device is used for injecting the transmission from each node at a predefined wavelength onto the ring and at the same time for accessing the transmission of the other nodes. Expressions are derived for the throughput of different network configurations. >

Analytic modeling of high-gain erbium-doped fiber amplifiers.

Abstract: We describe an analytic method that calculates accurately (within a 1.5-dB discrepancy with numerical models) the gain of an erbium-doped fiber amplifier. Amplified spontaneous emission (ASE) is taken into account so that the gain of ASE-saturated erbium-doped fiber amplifiers is calculated properly. It is effective for wavelength multiplexing (several signals) and for different pumping schemes (copropagating or counterpropagating or both).

Gain equalization multiwavelength lightwave systems using acoustooptic tunable filters

Abstract: An acoustooptic tunable filter is used to compensate for the gain spectrum variations in multiwavelength lightwave systems containing cascaded fiber amplifiers. Demonstrations of such systems using a circulating loop containing a fiber amplifier and an acoustooptic tunable filter have shown that differential gain compensations of up to 14 dB can be achieved for two arbitrary injected wavelengths. >

Distributed and Multiplexed Fiber Optic Sensors

Abstract: Many authors have recognised the unique advantages afforded in a number of application areas by the use of distributed fiber-optic sensor (DFOS) systems, which can be formed by combining fiber sensing and telemetry [1-11]. Approaches described to date can be categorized as being either 'intrinsic distributed' or 'quasi-distributed'. In the case of intrinsic distributed sensing, a single length of fiber forms an extended sensor element which senses the measurand field continuously over its entire length, whereas quasi-distributed sensing approaches utilize discrete sensor elements [12-15] arranged in a linear array or other, more geometrically versatile network topology.

Balanced optical amplifier

Abstract: A balanced doped fiber optical amplifier is disclosed which requires only a single wavelength division multiplexer to provide pump and signal inputs to multiple amplifier stages. In particular, a first section of doped fiber is coupled to an "input" port of the multiplexer and a second section of doped fiber is coupled to an "output" port of the multiplexer. First and second pump signals are coupled to the remaining ports to provide a counter-propagating pump signal to the first doped fiber section and a co-propagating pump signal to the second doped fiber section. The parameters of each doped fiber section (e.g., length, dopant concentration, pump power, pump wavelength) may be individually tailored to provide the desired results (pre-amplification or power boosting, for example). A plurality of balanced optical amplifiers may be cascaded to provide multi-stage amplifiers, and the pump signal levels may be controlled to provide gain equalization. Preferably, the balanced amplifier is spliceless and comprises only two sections of doped fiber, the multiplexer formed as a coupling region between the fibers.

Chromatic dispersion compensated optical fiber communication system

Abstract: An optical fiber communication system according to the invention comprises, in addition to conventional single mode (SM) optical fiber, dispersion compensating (DC) optical fiber. The DC fiber is selected such that its chromatic dispersion (DDC (λ)) and first derivative of the chromatic dispersion with respect to wavelength (D'DC (λ)) at a wavelength λ=λop have opposite sign from those of the SM fiber. Advantageously, the DC fiber is selected such that LDC ·DDC (λ)+L·D(λ) is approximately zero at λ=λop, and such that D'DC (λ) is approximately equal to --(L/LDC)·D'(λ) at λ=λop, where LDC and L are appropriate lengths of DC and SM fiber, respectively. Typically, L is much greater than LDC, and λop typically is about 1.5 μm, e.g., about 1.56 μm. Preferred embodiments of the invention have low chromatic dispersion over a substantial wavelength region (e.g., dispersion less than 1.5 ps/nm·km over at least 50 nm) that includes λo, facilitating wavelength division multiplexing.

Multiwavelength ring networks for switch consolidation and interconnection

Abstract: The authors investigate self-healing ring networks that utilize wavelength-division multiplexing (WDM) to provide survivable transport without the need for high-speed electronic add-drop multiplexers. They propose three specific multiwavelength ring networks, two designed for consolidation of switching resources at a single node on the ring, and one that supports symmetrical interconnection between all pairs of nodes. The maximum number of nodes and the maximum total capacity for the three networks are compared, as governed by the characteristics of the optical amplifiers and WDM techniques employed. It is found that all three networks are capable of supporting on the order of ten or more nodes with throughputs of 2.5 Gb/s to 10 Gb/s per node. The descriptions of the proposed networks assume an interoffice-network application, in which the nodes on the ring are central offices. >

Cascadability and fanout of semiconductor optical amplifier wavelength shifter

Abstract: Data at bit rates of 1 or 2 Gb/s are transferred through two cascaded, broadband wavelength shifters, which operate using gain saturation in semiconductor optical amplifiers. Such devices copy data from a modulated pump signal, in which the intensity of the marks is sufficient to significantly compress the gain of the amplifier, to a CW probe signal, producing the complement of the data. Furthermore, fanout (multicasting) is demonstrated in a single device by using two input CW probe signals. Such devices may find importance in wavelength division multiplexed systems requiring wavelength reuse and reassignment. >

2.5 and 10 Gb/s transmission experiments using a 137 photon/bit erbium-fiber preamplifier receiver

Abstract: An optical-preamplifier receiver with sensitivity of 137 photons/bit at 2.5 Gb/s and 1.530- mu m wavelength is presented. The sensitivity is 193 photons/bit at 10 Gb/s. The authors discuss the degradations from the quantum-limited value of 38 photons/bit. By employing an optical power amplifier at the transmitter, the authors demonstrate 2.5 Gb/s-250 km and 10 Gb/s-220 km transmission through dispersion-shifted fiber. >

Channel capacity optimization of chirp-limited dense WDM/WDMA systems using OOK/FSK modulation and optical filters

Abstract: Frequency chirp in semiconductor lasers that are directly modulated through carrier injection not only induces dispersion in long-haul single-mode fiber communication systems, but also causes energy loss and signal distortion when frequency selective elements such as Fabry-Perot filters are present. This effect is significant for high-bit-rate channels in a dense wavelength-division-multiplexed system in a LAN/MAN environment which requires narrow-band filters to suppress crosstalk from adjacent channels. A simulation approach is used to determine the channel capacity in the presence of chirp and crosstalk. The results show that a minimal channel spacing of less than 37 and 10 GHz with each channel operating at 2 Gb/s using OOK and FSK, respectively, can be achieved by a dense wavelength division multiple access system. It is also shown that this system performance can be optimized through adjusting various parameters of the laser and the filter. >

All-optical FM mode-locking of fibre laser

Abstract: A novel method of all-optical active mode locking which relies on the nonlinear process of crossphase modulation is described. Mode locking is achieved by using a stream of optical pulses propagating along a length of optical fibre to provide a periodic phase perturbation of the laser cavity. The technique is demonstrated using an erbium-doped fibre ring laser.

Remote pumping for active optical devices

Abstract: Optical amplifiers and other active optical components along a signal distribution path are remotely pumped by a common pump laser. The pump energy can be transmitted over the signal path or over a separate pump path. Pumping of rare earth doped optical fiber amplifiers, such as erbium doped fiber amplifiers is illustrated. The pump energy can be provided at about 1480 nanometers to take advantage of reduced attenuation at this wavelength along the fiber path.

Fast optical packet switching based on WDM

Abstract: An optical switch capable of routing a 3-Gb/s bit stream in 10-ns packets between ten different destinations is demonstrated. Switching time between destinations is 2 ns. The switch is based on wavelength division multiplexing (WDM) technology. It uses a fast tunable laser capable of addressing 24 discrete optical frequencies spaced by 40 GHz. >

Optical wavelength demultiplexing filter for passing a selected one of a plurality of optical wavelengths

Abstract: A method and apparatus for selecting an optical wavelength is provided incorporating a layer of silicon with two juxtaposed partially-reflective mirrors to provide a Fabry-Perot cavity and ohmic contacts to the silicon layer for heating the silicon layer to provide a temperature change to change its index of refraction. The invention overcomes the problem of mechanically tuning a Fabry-Perot cavity for wavelength division multiplexing (WDM).

Dispersion compensation in 1310 nm-optimised SMFs using optical equaliser fibre, EDFAs and 1310/1550 nm WDM

Abstract: A strategy is presented for the dispersion-compensated, flexible upgrading of existing 1310 nm-optimised interoffice fibre networks by using an optical equaliser fibre for dispersion compensation, an erbium-doped fibre amplifier for loss compensation and 1310/1550 nm WDM. This allows an upgrade to higher network capacities including long-distance, multigigabit per second SONET systems as required in future survivable interoffice networks. The feasibility of this concept is demonstrated with dispersion-free transmission at both 1310 and 1550 nm wavelengths over a 60 km conventional singlemode fibre, as well as with dispersion-compensated 1550 nm transmission over a 110 km conventional singlemode fibre at 2.5 Gbit/s.

Power requirements for erbium-doped fiber amplifiers pumped in the 800, 980, and 1480 nm bands

Abstract: The authors examine relative merits of exciting Er/sup 3+/ amplifiers at the three wavelengths for which high-power laser diodes are available at 800, 980, and 1480 nm Model calculations are confirmed by a detailed experimental comparison of the power requirements for pumping in the 800-nm band and at 980 nm To obtain comparable performance with respect to gain and noise figure, 7-8 dB more power is required when pumping in the 800-nm-band >

Optical time domain reflectometry in optical transmission lines containing in-line Er-doped fiber amplifiers

Abstract: Optical time domain reflectometry (OTDR) in an optical transmission line containing in-line Er-doped fiber amplifiers is investigated. The proposed Er-doped fiber amplifiers are based on optical circulators, which support both OTDR and digital signal transmission. The measurable limit of OTDR fault location in optical transmission lines containing in-line amplifiers is discussed. Fault location and 1.8-Gb/s digital signal transmission are demonstrated in a 316.9 km, optical transmission line constructed with three in-line Er-doped fiber amplifiers. >

Wavelength-division-multiplexing and -demultiplexing by using a substrate-mode grating pair

Abstract: We present theoretical and experimental studies of a novel substrate-mode grating pair structure for wavelength-division-multiplexing/demultiplexing applications. Normally incident coupling and on-axis output imaging with this device provide easier alignment with coupled optical fibers. We have designed and fabricated wavelength-division-multiplexing devices that are implemented by polarization-insensitive high-efficiency (> 85%) substrate-mode holograms. Three-channel demultiplexing experiments have also been successfully demonstrated with the limited available wavelength range of our diode-laser system.

Optical frequency division multiplexing transmission system

Abstract: An optical frequency division multiplexing transmission system for sending a large volume of information by a single optical fiber is disclosed. Each of an optical frequency division multiplexing transmitter equipment and an optical frequency division multiplexing receiver equipment has an optical filter having a periodic optical transmission characteristic therein. Each optical filter is stabilized with an absolutely-stabilized standard optical frequency. Each optical signal frequency is stabilized to a periodic transmission characteristic of the optical filter arranged in the optical frequency division multiplexing transmitter equipment, and each local frequency to a periodic transmission characteristic of the optical filter arranged in the optical frequency division multiplexing receiver equipment. Even in the case where no optical signal is applied to the optical frequency division multiplexing receiver equipment due to such causes as a fault of the transmission optical source or the breakage of an optical fiber, the local optical source frequency continues to be controlled in stable fashion.