Showing papers on "Wavelength-division multiplexing published in 1988"

LED spectral slicing for single-mode local loop applications

Abstract: An approach towards a single-mode local loop is presented in which each customer is given a dedicated wavelength channel by taking different wavelength slices from identical LEDs. This is accomplished by means of wavelength division multiplexing (WDM) components. Results from a fourchannel system operating at 2 Mbit/s over 2.2 km, together with a theoretical analysis of a ten-channel system, are presented.

Experimental demonstration of a passive optical subscriber loop architecture

Abstract: The authors report the experimental demonstration of a new passive optical subscriber loop architecture employing 20 channel WDM with 2 nm channel spacings. The experiment includes the demonstration of LED transmission in a dense, multi-wavelength single-mode fibre network. The experiment also features simultaneous, bidirectional transmission with both LEDs (384 kb/s) and DFB lasers (up to 1.2 Gb/s). >

A photonic knockout switch for high-speed packet networks

Abstract: A high-performance packet switch is discussed which uses a photonic interconnect fabric to route very-wideband data packets from input to output. Packet contention is accomplished using a much slower electronic controller, based on the knockout principle operating in parallel with the optical interconnect. Specifically, the use of a wavelength-division-multiplex fabric whereby high-speed (2-4 Gb/s) packets are regenerated before modulating a single-frequency laser at each switch input. The optical signals from various inputs are summed in a star coupler and then broadcast to the different coupler outputs. Each coupler is equipped with a small number (L) of tunable receivers arranged in a parallel manner, each preceded by a power splitter so that up to L simultaneous packets can be received by each output. The L packets so received are stored in an L-input one-output first-in first-out (FIFO) buffer so that the FIFO packet sequence is always guaranteed. Not only does this architecture achieve the best delay-throughput performance, but, remarkably, modularity is such that the optical complexity grows linearly with the number of switch ports./. >

High-speed data transmission on an optical fiber using a byte-wide WDM system

Abstract: The advantages and problems of using wavelength division multiplexing (WDM) to transmit byte-wide data in parallel through a single-mode optical fiber are studied. The principle problem which is particular to byte-wide transmission is shown to be bit skew caused by group delays of the different transmission wavelengths. The aggregate bit rate of the byte-wide link is shown to be equal to the aggregate bit rate of the serial link for all byte sizes. >

Multiwavelength optical crossconnect for parallel-processing computers

Abstract: A multiwavelength optical interconnection architecture for parallel-processing computers is presented. This fully connected, internally nonblocking network, using tunable lasers, requires only two optical fibres per node. Wavelength switching measurements (access times <20ns) and calculated throughput are presented. Critical target parameters are established for optical device development.

Wavelength-tunable 16 optical channel transmission experiment at 2 Gbit/s and 600 Mbit/s for broadband subscriber distribution

Abstract: We report a 16 optical-channel single-mode fibre transmission experiment based on dense-WDM and tunable-etalon channel selection. Experiments at 2 Gbit/s and 600 Mbit/s over 10 km of single-mode fibre show little crosstalk penalty when the optical channel spacing is 2 nm. The system architecture is useful for high-capacity broadband subscriber distribution.

Compensation of nonlinearity in semiconductor optical amplifiers

Abstract: The nonlinearity inherent in semiconductor optical amplifiers can cause adverse system effects, such as intermodulation distortion (IMD) in FDM systems, crosstalk in on/off-keying WDM systems, and pulse distortion in multi-Gbit/s on/offkeying systems. We present a practical, feed-forward linearisation scheme that is capable of reducing these effects significantly. A two-tone experiment confirms the reduction of the IMD by about 14 dB.

WDM coherent optical star network

Abstract: The results obtained with a fiber-optical star network using densely-spaced wavelength division multiplexing (WDM) and heterodyne detection techniques are reported. The system consists of three lasers transmitting at optical frequencies around 234000 GHz, spaced at a frequency interval of 300 MHz. The lasers are frequency-shift-key (FSK) modulated at 45 Mb/s. A 4*4 optical star coupler combines the three optical signals. The WDM signals received from one of the four outputs of the star coupler are demultiplexed by a heterodyne receiver. The minimum received optical power needed to obtain a bit-error rate of 10/sup -9/ is -61 dBm or 113 photon/bit, which is 4.5 dB from the shot noise limit. The degradation caused by co-channel interference was measured and found to be negligible when the channels, modulated at 45 Mb/s, are spaced by more than 130 MHz in the IF domain. These results indicate that a WDM coherent optical star network of this type has a potential throughput of 4500 Gb/s. >

Photorefractive dynamic optical interconnects

Abstract: We present and demonstrate a set of dynamic optical interconnects which are based on the double phase conjugate mirror with photorefractive wave mixing. These devices are bidirectional, self-adjusting, and controllable in real time. Uses in various interconnection modes are given.

A multibus train communication (AMTRAC) architecture for high-speed fiber optic networks

Abstract: A multibus train (ordered demand assignment) communication architecture, using the AMTRAC protocol (for efficient utilization of fiber-optic-based very-high-speed networks) is presented. Taking advantage of the emerging WDM (wavelength-division multiplexing) and FDM (frequency-division multiplexing) technologies, the proposed solution introduces a coordinated multichannel control combining the performance advantages of two known approaches for high-speed communication: multichannel and train protocols. As a result an AMTRAC-based high-speed network achieves channel utilization significantly higher than previous approaches. For a network consisting of N stations, with propagation delay to packet transmission time ratio given by a, the AMTRAC architecture reaches a capacity of 1/(1+a/N/sup 2/). >

Optical interference in lightwave subcarrier multiplexing systems employing multiple optical carriers

Abstract: It is shown that when multiple optical carriers are used in a subcarrier multiplexing system, the mixing of the optical fields in the photodetector leads to interference which may impose a limitation on the system bandwidth or the number or available channels.

Optical fiber communications system with optical fiber monitoring

Abstract: Optical communications fibers extend from a central office to subscribers' premises for carrying signals in both directions between optical transmitters and receivers. Each subscriber's optical receiver continuously reflects back to its fiber, and then to the central office, about 20 percent of the light which it receives. At the central office the reflected light is monitored in turn for each subscriber, and is correlated with the signal transmitted to that subscriber to provide a signal for optical time domain reflectometry of the respective subscriber's fiber connection.

Fault monitoring system for optical fiber communication systems

Abstract: A fault monitoring system for optical fiber communication system having a bidirectional optical amplifier between first and second optical fiber transmission lines. An optical monitoring signal of a first frequency different from frequencies of communication signal light of the optical fiber communication system is applied to the first input/output port of the bidirectional optical amplifier through the first optical fiber transmission line and then branched through a first optical filter passing therethrough of the first frequency to apply the branched optical monitoring signal of the first frequency to the second input/output port of the bidirectional amplifier. Another optical monitoring signal of a second frequency different from the first frequency and frequencies of the communication signal light is applied to the second input/output port of the bidirectional optical amplifier through the second optical transmission line and then branched through a second optical filter passing therethrough of the second frequency to apply the branched optical monitoring signal of the second frequency to the first input/output port of the bidirectional amplifier. A fault of the bidirectional amplifier can be detected by monitoring the optical monitoring signals of the first frequency and of the second frequency at respective ends of the first optical fiber transmission line and the second optical fiber transmission line.

Wavelength-routed optical networks using coherent transmission

Abstract: The authors consider future networks in which the electronic switches are replaced by passive optical nodes, using the 50-THz bandwidth of silica fiber to provide an optical ether with communications routed by wavelength. They identify a class of such networks which would use coherent transmission for wavelength selectivity, and optical amplifiers for simple multiwavelength repeaters. The motivation to investigate and develop these technologies thus stems from the potentially large reductions in the cost of switching, rather than the diminishing returns on transmission. The practicability and scope of such networks are considered. >

Inline tunable etalon filter for optical channel selection in high density wavelength division multiplexed fibre systems

Abstract: We report an inline angle-tuned Fabry-Perot etalon for optical channel selection in a high-density wavelength division multiplexed (WDM) direct-detection experiment. Feasibility is demonstrated in experiments with two different etalons: one for 5 distributed feedback (DFB) lasers in the 1550 nm region (1527–1559 nm), each spaced by 8 nm, and the other for 12 lasers (1527–1549nm), each spaced by 2 nm.

Four-port fibre-optic ring resonator

Abstract: A novel device is described, formed by taking one of the outputs of a 3 × 3 fused optical coupler back to one of the inputs to form a fibre optic ring resonator with two inputs and two outputs. The device can be used for narrowband wavelength division multiplexing and for switching of optical signals.

A passive photonic loop architecture employing wavelength-division multiplexing

Abstract: The authors present a fiber subscriber-loop architecture that uses multichannel wavelength-division multiplexing (WDM) to eliminate outside-plant electronics while providing each subscriber with dedicated channels to and from the central office. The approach has a number of attractive features, such as reduced maintenance requirements at remote sites in the loop plant and enhanced flexibility in the provisioning of services. The authors report an experimental demonstration of the architecture utilizing LEDs (light-emitting diodes) and low-cost receivers for narrowband ISDN (integrated services digital network) transmission and DFB (distributed feedback) laser for broadband transmission (up to 1.2 Gb/s). >

Microwave subcarrier multiplexing: new approach to wideband lightwave systems

Abstract: Wideband communication systems for providing voice, data, and video services to the subscriber over optical fibers are discussed. The principles of microwave-multiplexed lightwave systems are introduced, and several transmission experiments that demonstrate the concepts are described. >

Narrowband GaInAsP/InP waveguide grating-folded directional coupler multiplexer/demultiplexer

Abstract: We demonstrate a GaInAsP/InP waveguide, grating-folded directional coupler which provides narrowband (7 A FWHM) wavelength dependent interwaveguide coupling for multiplexing/demultiplexing applications.

A tunable 16 optical channel transmission/distribution experiment at 2 Gb/s and 600 Mb/s for broadband subscriber distribution

Abstract: Describes the first experiment demonstrating 16-optical-channel single-mode fiber transmission/distribution with tunable channel selection Based on high-density WDM and tunable optical etalons, 16 2-Gb/s channels (32 Gb/s total) can be distributed to the subscribers for selection For future B-ISDN (broadband integrated services digital network) applications such tunable multichannel broadband distribution technology is of great interest >

Crosstalk between intensity-modulated wavelength-division multiplexed signals in a semiconductor laser amplifier

Abstract: The performance of a 1.5- mu m Fabry-Perot type laser amplifier having two input signals at different wavelengths is experimentally studied. Crosstalk between the two signals at the output of the amplifier is measured. The crosstalk is strongly dependent on the input powers and on the signal gain, and is found to be very sensitive to the relative wavelengths of the input signals. The crosstalk can be either positive or negative, depending on the wavelength offsets. A theoretical model taking gain saturation and wavelength shift of the amplifier spectrum into account is shown to explain the experimental results well. Using this model, some general aspects on crosstalk in semiconductor laser amplifiers are discussed. >

An Introduction to Fiber Optics System Design

Abstract: 1. Introduction to Fiber Optics. Review of conventional transmission media. Introduction to fiber optics transmission. Transmission power-level diagrams. Radiation effects. Summary. Exercises. References. 2. Optical Fiber. Preliminaries. Composition. Manufacture. Dimensions. Characteristics. Fiber types. Fiber splicing. Light guidance. Other single-mode considerations. Comparison: metallic versus fiber waveguides. Radiation effects. Summary. Exercises. References. 3. Electro-Optical Conversion Devices. Electrical to optical conversion. Optical to electrical conversion. Coupling efficiency. Safety considerations. Radiation effects. Summary. Exercises. References. 4. Circuits: Transmitting and Receiving. Circuits. Transmitting circuits. Receiver circuits. Radiation effects. Summary. Exercises. References. 5. Modulation Techniques. Generalities. Analog modulation. Pulse analog modulation. Frequency modulation. Digital. Digital carrier. Choice of modulation technique. Summary. Exercises. References. 6. Systems. Systems considerations. Signal to noise ratio considerations. Bandwidth and attenuation. Loss budget. Bandwidth considerations. Size considerations. Weight considerations. Other considerations. High-frequency requirements. Costs. System loss-budget examples. Terrestrial system examples. Local area networks. Experimental systems. Radiation effects. Summary. Exercises. References. 7. Futures. Futures. Ultra low-loss fiber. Wavelength division multiplexing. Coherent detection techniques. Photonic switches. Photonic logic. Light-domain amplifiers. Integrated optics. Solitons. Optical phase conjugation. IV-VI compounds. New applications. Summary. Exercises. References. Appendices: A. Apparatus and Instrumentation. B. Useful Relations. C: Exercise Solutions. Glossary. Bibliography. Index.

Loop distribution using coherent detection (fiber optic networks)

Abstract: A novel architecture is described for point-to-multipoint distribution using coherent detection and a totally passive fiber bus. Coherent technology is used initially to provide transmission at rates of a few hundred Mb/s without the need for a local oscillator at each station. It is expected that this architecture can then be expanded via WDM (wavelength-division multiplexing) to transport multiple wavelengths as coherent technology matures. The performance of the proposed topology is analyzed and compared to that of previous bus structures using variable and fixed taps with direct-detection receivers. This performance analysis consists essentially of a loss budget calculation intended to determine the relative numbers of stations which each of the architectures could support. Because the rates and loop lengths are modest and the spectral width of the sources associated with coherent communication are very small, dispersion (or rise-time budgeting) is not expected to present any real limitation for the systems considered here. A performance analysis and comparison of three tree structures is presented. Engineering issues and open questions are discussed. >

Wavelength selection with nanosecond switching times using distributed-feedback laser amplifiers

Abstract: Wavelength selection with 1 ns switching times is demonstrated using DFB semiconductor laser amplifiers with net gain of 10 dB. Dynamic selection of packets from two wavelength-multiplexed 1.2 Gbit/s channels, separated by 0.23 nm, is demonstrated with BER<10/sup -9/.

Optical line test system

Abstract: PURPOSE: To supervise the test of a cable for all over a waveguide path without affecting a communication signal by providing a multiplexer/demultiplexer type optical coupler, a 1×N optical switch and a controller on the way of the optical fiber cable between optical transmission equipments. CONSTITUTION: The 1×N optical switch 11 selects the optical test light insertion port 92 of the multiplexer/demultiplexer type optical coupler 10 by the program control of the controller 14, and connects it to an optical pulse tester 12. The loss characteristic is measured and the fault position is detected in a coated optical fiber conductor 82 to be tested by a test optical pulse from the tester 12. Next, the switch 11 selects a port 94, and similarly conducts a test. By repeating the operation, a large number of coated optical fibers can automatically be tested and supervised for all over the optical fiber cables 31 and 32 between the light transmission terminal stations 1 and 2. By setting the wavelength area of a light receiver of the tester 12 to be a narrow one which does not receive a communication wavelength light, the test can be conducted without affecting communication. COPYRIGHT: (C)1990,JPO&Japio

Designs For High Channel Density Single-Mode Wavelength-Division-Multiplexers

Abstract: SUMMARY The multiplexer lengths and relative bandwidths for the various designs are summarised in Table 1. The lengths are also shown in figure 9 plotted as a functionof the required channel spacing. E 00 00.01 lens or waveguide spacing. x = 125 ymA = 1300 nm 2 tan e _ 1 twin and single-gratingwith identical lensessingle-grating with nonidentical lenses conventionalmultiplexer 10 100 Channel spacing, 3A / nm Figure 9. Multiplexer lengths. Although the conventional multiplexer has only areciprocal dependence on the channel spacing, itrequires either etched fibres 1I or waveguideconcentrators 181 to achieve high relative bandwidths.This would also increase the number of channels, whichis otherwise limited by the lens aberration. The twin - grating design, and the single- grating with identical lenses, offer very high relative bandwidths, but at theexpense of requiring long devices when multiplexingchannels with very close centre wavelengths. However, the single -grating multiplexer with dissimilar lensespossesses the same reciprocal dependence of length onchannel spacing as the conventional multiplexer. It alsohas the highest relative bandwidth of the multiplexersdescribed in this paper.

Fiber optic sensing apparatus for multiplexing a plurality of optical signals of different wavelengths over a single fiber optic cable

Abstract: An optical fiber system for gathering and transmitting data about a plurality of operating parameters in an aircraft gas turbine engine is disclosed. Broadband light from a light source is conducted through an optical fiber to a wavelength splitter/combiner which separates the received light signal into a number of discrete output wavelengths. Each wavelength is transmitted to a corresponding optical switch which is responsive to a monitored engine or environmental parameter to reflect all, none or a portion of the received light wavelength. The wavelength splitter/combiner multiplexes the reflected wavelengths into a single signal containing information pertaining to all monitored parameters.

Wavelength demultiplexing using bends in a single-mode optical fiber

Abstract: A method of wavelength demultiplexing is developed that makes use of the wavelength and bend-radius dependence of the pure bend loss at single radius bends in a single-mode fiber. The light leaving the fiber at a bend forms one output of the demultiplexer. Equations are derived that predict the bend radii for the most-efficient operation of the demultiplexer and the power extracted from the fiber at each wavelength. The demultiplexer operates over the wavelength range corresponding to V numbers from 2.4 to 1.6. A two-wavelength demultiplexer formed from 90 degrees bends is constructed and tested. Collection efficiencies of 70% and insertion losses of less than 2 dB are shown to be possible. Crosstalk isolation in excess of 40 dB can be achieved with the aid of optical wavelength filters. The performance of a three-wavelength demultiplexer is also considered. >