Showing papers on "Frequency-division multiplexing published in 1990"
TL;DR: The general technique of parallel transmission on many carriers, called multicarrier modulation (MCM), is explained, and the performance that can be achieved on an undistorted channel and algorithms for achieving that performance are discussed.
Abstract: The general technique of parallel transmission on many carriers, called multicarrier modulation (MCM), is explained. The performance that can be achieved on an undistorted channel and algorithms for achieving that performance are discussed. Ways of dealing with channel impairments and of improving the performance through coding are described, and implementation methods are considered. Duplex operation of MCM and the possible use of this on the general switched telephone network are examined. >
3,995 citations
TL;DR: Recent progress in multiwavelength networks are reviewed, some of the limitations which affect the performance of such networks are discussed, and examples of several network and switch proposals based on these ideas are presented.
Abstract: The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to time and space, in network and switch design The independence of optical signals at different wavelengths makes this a natural choice for multiple-access networks, for applications which benefit from shared transmission media, and for networks in which very large throughputs are required Recent progress in multiwavelength networks are reviewed, some of the limitations which affect the performance of such networks are discussed, and examples of several network and switch proposals based on these ideas are presented Discussed also are critical technologies that are essential to progress in this field >
1,382 citations
TL;DR: Recent advances in fully integrated acoustically tuned optical filters (ATOFs) for use in wavelength-division multiplexing (WDM) are reviewed and experiments in parallel processing of wavelength channels are described.
Abstract: Recent advances in fully integrated acoustically tuned optical filters (ATOFs) for use in wavelength-division multiplexing (WDM) are reviewed. Experiments in parallel processing of wavelength channels are described. The ATOF uses the photoelastic effect induced by a surface acoustic wave (SAW) to flip the polarization state of a narrow phase-matched band of wavelengths. A unique feature of the ATOF is that many wavelengths can be simultaneously and independently processed, because the associated SAW beams can be superimposed with negligible interaction at the drive levels required for complete polarization conversion. This parallel processing capability has been used to select as many as five out of eight laser channels in an experiment in which each channel was tagged by a separate microwave subcarrier. Polarization-independent devices are also discussed. A polarization-diversity ATOF that decomposes an input beam into TE (horizontal) and TM (vertical) components, interchanges TE and TM roles for the resonant wavelength, and reroutes the filtered beam into a spatially distinct port is described. >
179 citations
TL;DR: In this article, the limiting effects of four-wave mixing on optical frequency-division multiplexing (OFDM) systems are described and the theoretical and experimental results of the effects of FWM in OFDM systems are presented.
Abstract: The limiting effects of four-wave mixing on optical frequency-division multiplexing (OFDM) systems are described. The optical nonlinearity in a single-mode fiber imposes a fundamental limitation on the capacity of optical frequency-division multiplexed systems. In particular, four-wave mixing (FWM) crosstalk may severely degrade the system performance when the fiber input powers are large and/or the channel spacing is too small. Theoretical and experimental results of the effects of FWM in OFDM systems are presented. The theoretical results demonstrate the dependence of FWM on various system parameters. An analysis of FWM in both undirectional and bidirectional transmission systems is included. The receiver sensitivity degradation from FWM crosstalk is measured in a 16-channel coherent system. >
152 citations
TL;DR: In this article, the feasibility of a polarization-insensitive waveguide frequency selection switch for 10-GHz intervals and a frequency-shift-keying (FSK) direct-detection scheme employing a Mach-Zehnder filter is verified.
Abstract: A 100-channel optical frequency-division multiplexing (FDM) transmission/distribution experiment at 622 Mb/s is demonstrated for a fiber length of 50 km. The feasibility of a polarization-insensitive waveguide frequency selection switch for 10-GHz intervals and a frequency-shift-keying (FSK) direct-detection scheme employing a Mach-Zehnder filter is verified. The demodulation circuit employs a Mach-Zehnder filter and a balanced receiver, which utilizes optical power more efficiently than the Fabry-Perot filter. No receiver sensitivity degradation is observed due to interchannel crosstalk of the 128-channel tunable waveguide frequency selection switch (FS-SW) or fiber four-wave mixing for transmissions over a 50-km-long nondispersion-shifted (NDS) fiber and a 26-km-long dispersion-shifted (DS) fiber. >
132 citations
TL;DR: In this paper, the results for coherent digital subcarrier multiplexed (SCM) lightwave system experiments are described, including carrier-to-noise ratio, crosstalk, intermodulation distortion, and receiver sensitivity.
Abstract: The results for coherent digital subcarrier multiplexed (SCM) lightwave system experiments are described. A total of 20 frequency-shift-keyed (FSK) channels at 100 Mb/s each were transmitted on one optical carrier using microwave subcarriers in a multioctave configuration. A complete description of the system performance, including carrier-to-noise ratio, crosstalk, intermodulation distortion, and receiver sensitivity, is given. With a phase modulation index of beta =0.13, a receiver sensitivity of -27 dBm was obtained, representing a 14-dB improvement over a 20-channel direct detection SCM system. Crosstalk due to adjacent channels is negligible with a channel spacing of twice the data rate (200 MHz). Theoretical and experimental results are compared, and conditions for optimal performance as a function of channel number and phase modulation index are discussed. >
110 citations
TL;DR: In this article, a 1.2-Gb/s optical PSK heterodyne transmission system operating at 560 Mb/s and 1 2 Gb/s was studied.
Abstract: Modulation and demodulation techniques are described for an optical PSK heterodyne transmission system operating at 560 Mb/s and 1.2 Gb/s. Performance limitations affecting the receiver sensitivity in a 1.2-Gb/s DPSK system, such as laser phase noise, phase modulation depth, IF center frequency deviation, and local laser power, are studied. High receiver sensitivities for PSK systems were achieved. The applicability of the Mach-Zehnder modulator as a phase modulator for 1.2-Gb/s DPSK is also demonstrated. A 1.2-Gb/s DPSK transmission of over 100 km, using polarization diversity with novel polarization-insensitive automatic frequency control in an attempt to overcome signal fading caused by polarization fluctuation in the transmitting fiber, is also described. A receiver sensitivity of less than -42.8 dBm and varying within 1.4 dB for all states of polarization was achieved. A multichannel high-definition TV (HDTV) transmission experiment using a DPSK polarization-diversity tunable receiver is described. >
96 citations
TL;DR: In this paper, three component concepts for use in high-density wavelength division multiplexed optical systems are described, and applications envisaged for these components include broadband overlay for subscriber access networks and ultrahigh-capacity packet switching for telecommunications or parallel processing computer applications.
Abstract: Three component concepts for use in high-density wavelength-division-multiplexed optical systems are described. The applications envisaged for these components include broadband overlay for subscriber access networks and ultrahigh-capacity packet switching for telecommunications or parallel processing computer applications. The components each use a dispersive optical grating and integrated array of optoelectronic transducers to form a component with precisely defined multiple operating wavelength channels. Multichannel laser transmitter and direct detection receiver components suitable for up to about 50 independent channels separated by 1-2 nm in the 1300- to 1600-nm-wavelength range are described. >
67 citations
TL;DR: It was found that NDS fibers operated at a wavelength of 1550 nm can be widely deployed in multichannel systems both for the long-haul and information distribution transmissions, if the signal waveform distortion due to fiber chromatic dispersion is precluded.
Abstract: Transmission limitations due to stimulated Brillouin scattering and four-wave mixing processes are investigated for optical frequency division multiplexing (FDM) systems. The applicability of the dispersion-shifted (DS) and nondispersion-shifted (NDS) fibers is discussed, taking account of channel frequency separation, total channel numbers, input signal power, transmission length, and receiver sensitivity degradation. Experimental results on Brillouin gain spectra and the wave generation efficiency in four-wave mixing processes are also presented to discuss the applicability of the two types of single-node fiber. It was found that NDS fibers operated at a wavelength of 1550 nm can be widely deployed in multichannel systems both for the long-haul and information distribution transmissions, if the signal waveform distortion due to fiber chromatic dispersion is precluded. The delay equalizer will be useful for a high-speed system employing bit rates over 10 Gb/s and repeaterless spans over 300 km. For such an application, DS fiber is preferable. Concerning information distribution network applications, the NDS fiber should be more attractive as a transmission medium for FDM system applications. >
65 citations
TL;DR: A novel approach is described that utilizes a passive star coupler for distribution, a multiplicity of frequency-shift keyed tunable lasers to provide a frequency division multiplexed (FDM) network, and a tunable optical fiber Fabry-Perot filter to select the channels and convert the FSK signal to ASK (amplitude-shift keying) for direct detection.
Abstract: High-performance optical data networks of the future may interconnect hundreds of users at gigabit rates for a reasonable cost. A novel approach is described that utilizes a passive star coupler for distribution, a multiplicity of frequency-shift keyed (FSK) tunable lasers to provide a frequency division multiplexed (FDM) network, and a tunable optical fiber Fabry-Perot filter to select the channels and convert the FSK signal to ASK (amplitude-shift keying) for direct detection. The design of high-speed FDM-FSK direct detection networks and the performance of critical devices, such as tunable FM lasers, tunable filters, integrated star couplers, and optical amplifiers, are reviewed and discussed. >
65 citations
03 Jun 1990
TL;DR: The multihop architecture, which provides a way of tapping the capacity potential available in lightwave networks, is described and solutions in which the traffic flows over a derived connectivity diagram such that the largest flow on any link is minimized are sought.
Abstract: The multihop architecture, which provides a way of tapping the capacity potential available in lightwave networks, is described. Within this architecture, each network node is equipped with some small number of transmitters and receivers, each of which can communicate on one wavelength. Transmitters and receivers are connected to an optical medium, which is physically configured in such a way that the entire spectrum of wavelengths in use is potentially accessible by each node. Then, an assignment of transmit and receive wavelengths to each node defines the logical connectivity among nodes. Furthermore, the use of optically agile transceivers (i.e. slowly tunable lasers or optical filters) permits the logical connectivity to be updated in response to changing traffic patterns and failure/recovery of nodal transmitters and receivers. The flow and wavelength assignment problem is studied. Solutions in which the traffic flows over a derived connectivity diagram such that the largest flow on any link is minimized are sought. Examples of the resulting connectivity diagram and traffic flow are presented for selected nonuniform point-to-point traffic matrices. >
TL;DR: In this article, the design, performance, and optical link requirements are discussed for a 2-Gb/s subcarrier-multiplexed (SCM) system with 20 microwave subcarriers modulated at 100 Mb/s and using a frequency-shift-keyed format.
Abstract: Microwave subcarriers have been used to demonstrate an optical communication system suitable for the distribution of digital video channels. The design, performance, and optical link requirements are discussed for a 2-Gb/s subcarrier-multiplexed (SCM) system with 20 microwave subcarriers modulated at 100 Mb/s and using a frequency-shift-keyed format. The system uses the 2-6-GHz bandwidth and represents the first example of an SCM system using more than one octave of bandwidth. The bit error rate was measured for all 20 channels; results for five typical channels are shown and discussed. The performance results show that a digital SCM approach is attractive in an optical link for a multichannel wide bandwidth video distribution system made from standard microwave components. >
30 Sep 1990
TL;DR: In this paper, a combined demultiplexer and demodulator using digital signal processing is described which uses frequency domain filtering to separate the signals and a shared structure for the demodulation process.
Abstract: Low to medium bit rate digital transmission formats are increasingly being used for satellite communications to reduce the size and cost of earth stations. A combined demultiplexer and demodulator using digital signal processing is described which uses frequency domain filtering to separate the signals and a shared structure for the demodulation process. A special-purpose, high-speed fast Fourier transform (FFT) processor is designed which operates on a 20-MHz bandwidth that contains carriers ranging in bit rate from approximately 1.5 to 11.3 Mb/s. An interpolating filter is used between the demultiplexer and the demodulator to provide the two samples per symbol required for the demodulation process. The major components of the demultiplexer/demodulator are described. The implementation concentrated on designs using low-power complementary metal-oxide semiconductor (CMOS) circuitry. In addition, a testbed was designed and fabricated to provide the multicarrier inputs needed to demonstrates system capability. >
TL;DR: Wavelength-selective characteristics in the AO module are established and the crosstalk from other wavelengths is found to be reduced by decreasing slightly the switching transfer efficiency.
Abstract: Optical integrated switching systems using collinear acoustooptic (AO) interactions for wavelength division multiplexing (WDM) systems are discussed. The AO switch module has excellent advantages compared to electrooptic switches. Optical WDM signals can be wavelength-selectively switched by frequency multiplexed surface acoustic waves. WDM switching systems are proposed as an application of this AO switch, and optical insertion loss, crosstalk, and optical frequency shift are discussed. Wavelength-selective characteristics in the AO module are established. The crosstalk from other wavelengths is found to be reduced by decreasing slightly the switching transfer efficiency. The wavelength-selective switching was experimentally demonstrated with a slab-type module of a 4-mm interaction region, where the WDM interval of 25.2 AA was realized. This wavelength interval can be decreased by increasing the interaction length. >
TL;DR: In this paper, a total of 16 DFB lasers with 10 GHz frequency spacing were combined to transport 160-channel FM television signals to 16 locations; each link distance was 9 km with an average power margin of 7.5 dB.
Abstract: A total of 16 DFB lasers with 10 GHz frequency spacing were combined to transport 160-channel FM television signals to 16 locations; each link distance was 9 km with an average power margin of 7.5 dB. The 16 optical carriers were simultaneously modulated by a composite of 10 FM-video signals. A high-finesse optical Fabry–Perot etalon with a half-intensity width of about 1.5 GHz and a free spectral range of 4 nm was used, both as an optical channel filter and as a frequency discriminator. An erbium doped fibre amplifier was used to provide a net gain of 9.2 dB.
02 Dec 1990
TL;DR: The flow and wavelength assignment problem is studied, and solutions are sought which flow the traffic over a derived connectivity diagram such that the largest flow on any link is minimized.
Abstract: Within the multihop architecture, each network node is equipped with some small number of transmitters and receivers, each of which can communicate on one wavelength. Transmitters and receivers are connected to an optical medium, which is physical configured in such a way that the entire spectrum of wavelengths in use is potentially accessible by each node. Then, an assignment of transmit and receive wavelengths to each node defines the logical connectivity among nodes. The use of partially agile transceivers provides some ability to update the logical connectivity in response to changing traffic patterns and failure/recovery of nodal transmitters and receivers. The flow and wavelength assignment problem is studied, and solutions are sought which flow the traffic over a derived connectivity diagram such that the largest flow on any link is minimized. Examples of the resulting connectivity diagram and traffic flow are presented for selected nonuniform point to point traffic matrices, and for different ranges of transmitter/receiver tunability. >
TL;DR: In this paper, the effect of correlation between the gate and the drain HEMT noise sources and the design of tuning networks to obtain partial noise cancellation were investigated, and an optimization algorithm was used to determine the tuning elements values for minimizing noise of 16 dB for a 60-video-channel subcarrier multiplexing (SCM) system, and 12 dB for an 120-channel system.
Abstract: An analysis of tuned optical-receiver noise performance for microwave subcarrier multiplexed lightwave systems is presented. The effect of correlation between the gate and the drain HEMT noise sources and the design of tuning networks to obtain partial noise cancellation were investigated. Anoptimization algorithm is used to determine the tuning elements values for minimizing noise of 16 dB for a 60-video-channel subcarrier multiplexing (SCM) system, and 12 dB for a 120-channel system, which allows a significant increase in passive optical network distribution capacity. Design results for tuned front-end receivers encompassing the effects of p-i-n, HEMT, and SCM band parameters are presented. >
TL;DR: Analyses of four broadband fiber-optic subscriber loop architectures indicate that splitter-based passive loops share electronics more effectively among subscribers than loop architectures requiring dedicated (per-subscriber) electronic interfaces, resulting in projected cost advantages for the splatter-based networks.
Abstract: Analyses of four broadband fiber-optic subscriber loop architectures, including active (high-speed time division multiplexing (TDM)-based) and passive (dense wavelength division multiplexing (WDM)-based, WDM-based with an analog subcarrier-multiplexing overlay, and splitter-based) double-star topologies, are presented. The analyses focus on specific demonstrated architectures and use component cost projections based on learning curves to estimate future network costs on a per-subscriber basis. Also investigated is the sensitivity of projected cost-per-subscriber to remote multiplexing node size and to double-star prove-in distance. The results indicate that the four architectures have very different double-star prove-in distances and that loop costs are minimized for much smaller remote node sizes than active loops, thus permitting cost-effective deployment of passive loops for smaller groups of subscribers. In addition, cost breakdowns for the four architectures indicate that splitter-based passive loops share electronics more effectively among subscribers than loop architectures requiring dedicated (per-subscriber) electronic interfaces, resulting in projected cost advantages for the splitter-based networks. >
Patent•
29 Aug 1990TL;DR: In this paper, an optical frequency division multiplexing (OFDM) transmitter is described, which comprises a plurality of optical transmitters having different optical frequencies, an optical combiner multiplexer having optical signals outputted by the different transmitters, and an optical filter having passbands, each of which is approximately in accordance with the frequency of each of the signals.
Abstract: An optical frequency division multiplexing transmitter is disclosed, which comprises a plurality of optical transmitters having different optical frequencies; an optical combiner multiplexing optical signals outputted by the different optical transmitters; and an optical filter having passbands, the frequency of each of which is approximately in accordance with the frequency of each of the signals, in which the signal thus multiplexed is inputted.
TL;DR: In this article, the progress towards developing AM lightwave links for the transmission of multiple TV signals is reported, while the signal quality objectives and transmission distances are appropriate for CATV trunking, the technology is expected to have applicability to the distribution of video signals in the subscriber loop.
Abstract: The progress towards developing AM lightwave links for the transmission of multiple TV signals is reported. While the signal-quality objectives and transmission distances are appropriate for CATV trunking, the technology is expected to have applicability to the distribution of video signals in the subscriber loop. Highly linear 1.3- mu m distributed feedback (DFB) lasers designed expressly for analog requirements are used to transmit 42 continuous wave carriers according to the standard US CATV frequency plan. For the best lasers, when evaluated over 12 km of fiber, carrier to noise was >52 dB, composite second-order distortion was >70 dBc, and composite triple beat was >70 dBc. The relationship between measurements with continuous wave carriers and actual video signals is discussed. System design rules are offered. Properties that lead to superior analog performance are discussed. Data from 700 links indicate that composite third-order distortion generally scales with product count but that composite second-order distortion has a significant frequency-dependent component. >
TL;DR: FM-FDM (frequency division multiplexing) optical transmission equipment has been developed for 34-channel MUSE HDTV signals to realize optical CATV (cable television) systems and the method of system design is clarified for an optical trunk line CATV system.
Abstract: FM-FDM (frequency division multiplexing) optical transmission equipment has been developed for 34-channel MUSE HDTV (high-definition television) signals to realize optical CATV (cable television) systems. The equipment uses an LD (laser diode) with a 1.3 mu m wavelength, a single-mode optical fiber, and an avalanche photodiode (APD). A good picture is received after a 42 km transmission. A part of the multiplexed signals is distorted near or below the threshold of an LD. When the number of transmission channels is small and the total optical modulation depth is large, this nonlinearity governs the power ratio of an FM signal to one distortion component-the DU ratio. However, when the number of transmission channels is large, the DU ratio is determined by the effective optical modulation depth rather than the total optical modulation depth. Furthermore, the method of system design is clarified for an optical trunk line CATV system. If no restriction on the transmission bandwidth of optical devices exists, approximately 30 km transmission of 100-channel MUSE HDTV signals is available with a received CN ratio of 17.5 dB. >
TL;DR: Frequency-division multiple access appears in general to be the more capable system, because CDMA can better absorb Doppler and multipath effects and permits higher rate coding.
Abstract: A comparison between frequency-division multiple access (FDMA) and code-division multiple access (CDMA) when both methods operate in the mobile satellite communication environment is presented. The mobile satellites under consideration use multiple beams or scan beam antennas and employ frequency reuse of the allocated L-band frequency spectrum. Because CDMA can better absorb Doppler and multipath effects and permits higher rate coding, it appears in general, with practical considerations set aside, to be the more capable system. >
NEC1
TL;DR: In this paper, a coherent optical frequency-division-multiplexing (FDM) experimental system for an optical CATV distribution service has been developed, which employs a channel frequency spacing locked optical FDM transmitter and a random access optical heterodyne receiver.
Abstract: A coherent optical frequency-division-multiplexing (FDM) experimental system for an optical CATV distribution service has been developed. This system employs a channel frequency spacing locked optical FDM transmitter and a random access optical heterodyne receiver. In the transmitter, ten 1.54- mu m wavelength tunable distributed-Bragg-reflector laser-diode (DBR LD) modules were FSK modulated with a 400-Mb/s PN pattern. A reference pulse method is used for channel space control. Individual channel spacings for ten LDs are stabilized to 8 GHz. The random access optical heterodyne receiver is realized with a wavelength tunable local DBR LD, polarization diversity reception technique, and random access automatic frequency controller. A current address method realizes the random access function. The results of a ten-channel FDM transmission experiment carried out to evaluate these techniques are presented. It is estimated that over 80 channel high-definition TV signals can be distributed to 2000 subscribers with 500-GHz frequency tunable DBR LD. The feasibility of expanding the subscriber number to over 10000 was confirmed by an experiment with a traveling-wave optical amplifier. >
TL;DR: The approach achieves high throughput by reusing the same channels, that collectively occupy a tiny fraction of the optical band, among all interconnecting links and, with the exception of large-dimensional switch arrays, employs readily available technology.
Abstract: The technical feasibility of a lightwave communication system capable of providing service to thousands of subscribers within cities or large suburban areas is examined. Each subscriber in this system has available upon demand an aggregate bit rate of up to 100 Mb/s. The aggregate bit rate of the entire network is on the order of 5 Tb/s. The network topology is that of a star-on-star wherein each subscriber line terminates on one of a multitude of remote concentrators. Each high-speed link from a remote concentrator to a centrally located time-multiplexing photonic switch consists of a single-mode fiber carrying several wavelength-division multiplexed (WDM) channels. Each channel operates in a time-division multiplexed (TDM) mode at a data rate of 2 Gb/s and is powered by a multimode laser. No regeneration is required at the central switch, and at the remote concentrators, each channel is terminated by a direct-detection receiver. The approach achieves high throughput by reusing the same channels, that collectively occupy a tiny fraction of the optical band, among all interconnecting links and, with the exception of large-dimensional switch arrays, employs readily available technology. >
TL;DR: The results obtained with a densely spaced frequency division multiplexing (FDM) optical star network providing random channel selection by a digitally tuned high-sensitivity heterodyne receiver indicate that this system has potential throughput of 2000 Gb/s.
Abstract: The results obtained with a densely spaced frequency division multiplexing (FDM) optical star network providing random channel selection by a digitally tuned high-sensitivity heterodyne receiver are presented. The experimental system consists of six 200-Mb/s frequency-shift keyed (FSK) modulated channels, spaced by 2.2 GHz and multiplexed by a star coupler. Channel selection is performed by a computer-controlled random-access heterodyne receiver having a sensitivity of 74 photons/b at a BER of 10/sup -9/, which is 1.7 dB from the quantum limit. The digital-tuning random-access capability (which depends on the frequency-tuning current relationship of the local oscillator (LO) laser) is protected against frequency drifts of the LO laser. The receiver can also detect the absence of a selected channel. In this case, the receiver locks to the next available channel and displays which channel is received instead. The results obtained indicate that this system has potential throughput of 2000 Gb/s. >
TL;DR: Topics covered include optical FDM transmission/distribution experiments; augmenting dense WDM with subcarrier multiplexing; the feasibility of distributing analog and digital video signals to 4096 subscribers; dense W DM component technology advances; and demultiplexing of WDM signals.
Abstract: Since great progress has occurred recently, a short summary is presented of some of the most significant results reported in a period of six months. Topics covered include optical FDM (frequency division multiplexing) transmission/distribution experiments; augmenting dense WDM with subcarrier multiplexing; the feasibility of distributing analog and digital video signals to 4096 subscribers; dense WDM component technology advances; and demultiplexing of WDM signals. >
TL;DR: An analysis of crosstalk in multichannel wavelength-division multiplexing (WDM) systems is presented, deriving new expressions for system degradations and taking into account both receiver design and the practical limitations of regenerator electronics.
Abstract: An analysis of crosstalk in multichannel wavelength-division multiplexing (WDM) systems is presented, deriving new expressions for system degradations and taking into account both receiver design and the practical limitations of regenerator electronics. This theoretical study is corroborated by measured results obtained on a commercially available digital transmission system and is then used to determine the optimum multiplexer design for multichannel wavelength division multiplexed systems. From this study, the optimum multiplexer design for giving acceptable transmission performance is determined. >
TL;DR: The performance of a 5-GHz-spaced, 16-channel frequency selection switch (FS-SW) for optical frequency division multiplexing (FDM) distribution systems is described and the desired channel can be selected successfully from among 16 optical carriers under an average crosstalk level of less than -20 dB.
Abstract: The performance of a 5-GHz-spaced, 16-channel frequency selection switch (FS-SW) for optical frequency division multiplexing (FDM) distribution systems is described. The silica waveguide-type FS-SW is constructed with four serially connected periodic filters integrated on a silicon chip. The required crosstalk level for each periodic filter of the FS-SW was estimated to be -21.0 dB for a 16-channel FS-SW and 23.6 dB for a 128-channel FS-SW. Crosstalk can be independent of the power coupling ratio of the 3-dB-coupler regions by choosing suitable connecting configurations for the periodic filters. A controller for the switch is also described and the desired channel can be selected successfully from among 16 optical carriers under an average crosstalk level of less than -20 dB. >
TL;DR: In this article, a new form of diode laser source for wavelength division multiplexing (WDM) applications is reported. The source is designed to operate in systems requiring wavelength separations between channels of more than 1 nm and provides exact control of channel separation with low crosstalk.
Abstract: A new form of diode laser source for wavelength-division multiplexing (WDM) applications is reported. The source has been designed to operate in systems requiring wavelength separations between channels of more than 1 nm and provides exact control of channel separation with low crosstalk. Simultaneous multiwavelength generation is also possible. >
TL;DR: In this article, the authors report the experimental demonstration of a new passive fiber-optic subscriber loop architecture, which provides each of 16 subscribers with a dedicated, two-way broadband channel for switched services, as well as with an array of broadcast video channels.
Abstract: We report the experimental demonstration of a new passive fibre-optic subscriber loop architecture. The architecture provides each of 16 subscribers with a dedicated, two-way broadband channel for switched services, as well as with an array of broadcast video channels. The dedicated channels are provided via 16-channel dense wavelength-division multiplexing (WDM), and the broadcast channels are transported over the same loop fibre via FM subcarrier multiplexing. A number of potential advantages of this hybrid (switched/broadcast) approach are foreseen.