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Issue 7 • Date Sep 1990

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Displaying Results 1 - 22 of 22
  • Distributed feedback laser diode and module for CATV systems

    Publication Year: 1990 , Page(s): 1359 - 1364
    Cited by:  Papers (14)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    Harmonic distortion of distributed feedback laser diodes (DFB-LDs) for analog transmission systems is investigated. It is shown that, under a modulation frequency of less than 1 GHz, the harmonic distortion depends on the nonlinearity of the light output power-current (P-I) curve under the continuous wave (CW) condition, which is determined by the coupling constant κ L, and that the distortion can be minimized at κ L~1. A 1.3 μm wavelength InGaAsP DFB-PPIBH (p-substrate partially inverted buried heterostructure) LD and its module, with low distortion by the control of a coupling constant, have been developed View full abstract»

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  • Fiber induced distortion in a subcarrier multiplexed lightwave system

    Publication Year: 1990 , Page(s): 1296 - 1303
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    The harmonic and intermodulation distortions induced by fiber dispersions are analyzed. The concept of the common frequency (or common period) is introduced for the analyses of intermodulation. It is shown that both the magnitude and shape of the sum terms of the intermodulation are quite similar to those of the harmonic distortions of the same order. The difference terms of the intermodulation are much smaller if the subcarrier frequencies are not far apart from one another. It is concluded that the influence of dispersion-induced distortions depends on the subcarrier frequency, the dispersion constant, the length of the fiber, and the modulation indexes. Accompanied by the development of high-frequency and large capacity systems and single-mode lasers with extra narrow spectrum, the dispersion-induced distortions may become one of the most important factors in determining information capacity and transmission distance View full abstract»

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  • Frequency-dependent distortions of composite triple beat in lightwave CATV transmission systems

    Publication Year: 1990 , Page(s): 1365 - 1368
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The frequency-dependent distortion of composite triple beat (CTB) for analog AM multichannel lightwave transmission systems is studied. A modified circuit model which takes into account the small signal behavior of the leakage path is developed, and it is shown that it is adequate to describe the measured frequency-dependent behavior of CTB in a 42-channel load lightwave CATV (cable television) transmission system using a cap-mesa buried-heterostructure (CMBH) distributed-feedback (DFB) laser inside the transmitter module View full abstract»

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  • FM-FDM optical CATV transmission experiment and system design for MUSE HDTV signals

    Publication Year: 1990 , Page(s): 1257 - 1267
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (908 KB)  

    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 μm 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 View full abstract»

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  • A hybrid architecture for analog video broadcast and B-ISDN services in customer premises networks

    Publication Year: 1990 , Page(s): 1327 - 1339
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1296 KB)  

    The use of SCM (subcarrier multiplexing) transmission to deliver broadcast analog video signals within a CPN (customer premises network) as an overlay to an all-digital B-ISDN (broadband integrated services digital network) is considered. The feasibility of a proposal where the analog and digital signals are carried on different wavelengths is shown. An architecture for an optical CPN, termed H-Bus and incorporating emerging broadband SONET and ATM (asynchronous transfer mode) standards, is taken as a baseline for the delivery of switched digital, two-way voice, data, and video services. An optical overlay for the distribution of analog, broadcast video services using subcarrier multiplexing is considered. Several key alternatives associated with the delivery of broadcast video services are assessed, including signal quality, number of simultaneous channels, number of user terminals to be served, and modulation format. These issues are considered in terms of their impact on the interface with the public local exchange network and on the complexity, topology, and cost of the CPN View full abstract»

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  • Overmodulation in subcarrier multiplexed video FM broad-band optical networks

    Publication Year: 1990 , Page(s): 1285 - 1289
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    The probability of an SCM (subcarrier multiplexed) signal falling outside the linear region of a laser diode is calculated in order to determine the overmodulation that may be practically employed for multichannel video distribution in single-octave SCM networks. The overmodulation is predicted as a function of the number of subcarriers in single-octave SCM systems supporting up to about 70 FM video channels, for SNRs (signal-to-noise ratios) of 47 dB (I/PAL), and 56 dB (M/NTSC). The RMS optical modulation index (OMI) is demonstrated to be a more useful performance parameter than the linear OMI in SCM systems carrying a large number of channels. A 47 dB weighted SNR (with 4 dB margin) is deemed sufficient for acceptable picture quality in cable distribution systems, whereas a 56 dB value would be required for long-distance point-to-point optical links. RMS OMI values of around 70 and 50, respectively, can be employed View full abstract»

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  • Optical receiver for VHF multichannel video transmission

    Publication Year: 1990 , Page(s): 1382 - 1386
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Optical receivers for multichannel TV transmission in the VHF band are analyzed and tested from the viewpoints of linearity, sensitivity, and frequency response. Photodiodes and avalanche photodiodes are compared for use as a front-end detector. Optimization of the preamplifiers is studied in terms of both configurations and biasing conditions. Improvement of frequency characteristics, using a Percival coil, is also investigated. It is concluded that a receiver using a photodiode can attain as high a sensitivity as and a greater linearity (around 5 dB) than one using an avalanche photodiode View full abstract»

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  • Design and performance of a fiber-optic video distribution system using BPSK microwave subcarriers

    Publication Year: 1990 , Page(s): 1304 - 1312
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    The design and performance of a fiber-optic video distribution system using bi-phase shift keyed (BPSK) microwave subcarriers to provide each subscriber with 20 107 Mb/s digitized video channels and one voice/data channel at 2.048 Mb/s are described. The combined microwave subcarriers are used to intensity-modulate a 1.3 μm single-mode laser, one dedicated to each subscriber. The penalty in system sensitivity resulting from the use of more than one subcarrier is calculated. The design and implementation of subcarrier generation, BPSK modulation, multiplexing/demultiplexing, and subscriber receivers are described. An experiment procedure to obtain an optimum laser driver level is also described. A bit error rate of 10-9 or less is achieved at a received optical power of -12 dB (1 mW) for all channels for each subscriber View full abstract»

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  • Subcarrier multiplexed coherent lightwave systems for video distribution

    Publication Year: 1990 , Page(s): 1268 - 1275
    Cited by:  Papers (24)  |  Patents (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    The application of subcarrier multiplexing techniques to coherent lightwave systems designed for video transmission is described. The theory of the intrinsic receiver sensitivity of multichannel coherent SCM (subcarrier multiplexing) systems is presented. Specific implementations of SCM coherent systems transmitting 60 FM video channels and 20 100 Mb/s FSK (frequency shift keying) channels are described. It is shown that a simple phase noise canceling circuit can be implemented, which allows these systems to be built with wide-linewidth DFB (distributed feedback) lasers. Several applications of multichannel coherent SCM systems to video distribution networks are proposed View full abstract»

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  • AM video on fiber in CATV systems: need and implementation

    Publication Year: 1990 , Page(s): 1229 - 1239
    Cited by:  Papers (43)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (996 KB)  

    Limitations of current CATV (cable television) system architecture are described. A hybrid optical fiber/coaxial cable architecture is introduced, and the performance levels necessary for the optical portions of that system are explored. Optical device performance is outlined as it applies to such a hybrid system, and various optical components with the potential to be used in such a system are examined. It is concluded that the hybrid fiber backbone/coaxial distribution architecture outlined meets a number of needs within the CATV industry. It provides a means of significantly improving the operation of CATV plant while laying the foundation of future evolution View full abstract»

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  • Synchronous quantized subcarrier multiplexing for transport of video, voice, and data

    Publication Year: 1990 , Page(s): 1351 - 1358
    Cited by:  Papers (2)  |  Patents (69)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    A quantized subcarrier multiplexing approach for the transmission of video, voice, and data information over optical fiber networks is explored. The basis of this technique is to utilize a single high-speed analog-to-digital converter to digitize a composite analog signal. Conventional subcarrier multiplexing methods are used to form the composite from multiple NTSC video, voice, and data signals. The process of synchronous multiplexing, quantization, serialization, transmission, and waveform recovery is explored for an experimental prototype system. Noise performance and the impact on laser linearity requirements are discussed View full abstract»

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  • Dual parallel modulation schemes for low-distortion analog optical transmission

    Publication Year: 1990 , Page(s): 1377 - 1381
    Cited by:  Papers (60)  |  Patents (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The use of two integrated-optical modulators operated in parallel to attain low-distortion analog optical transmission is examined. This static feedforward approach achieves significantly improved linearity at the expense of small increases in the required optical power and moderate increases in the required drive voltage. A novel variation that uses the unique characteristics of an integrated-optical modulator to correct the dominant quadratic distortion of a directly modulated laser is proposed View full abstract»

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  • An evolutionary transport structure for local loop distribution using RF subcarriers

    Publication Year: 1990 , Page(s): 1340 - 1350
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    An evolutionary transport structure for local loop distribution based on RF subcarrier multiplexing and wavelength-division multiplexing is discussed. Issues relating to technology and cost are discussed. The transport structure provides private, high-bit-rate, premium services to business sites, and broadcast, low-bit-rate, low-cost services to residential users. The structure is transparent to various protocols or modulation schemes and can be configured to suit different needs. Up to 60 analog FM broadcast video channels downstream and 4 analog FM video channels upstream (or a single 155-Mb/s broadband ISDN channel) per subscriber can be provided for 16 subscribers per fiber feeder. It is possible that the transport structure could be deployed affordably in the near future. Future upgrades and expansions are possible because the transport structure is compatible with most promising future technologies. Various tradeoffs are also discussed View full abstract»

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  • Fiber-optic transmission of microwave 64-QAM signals

    Publication Year: 1990 , Page(s): 1320 - 1326
    Cited by:  Papers (13)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    Experimental results on fiber-optic transmission of microwave 64-level quadrature amplitude modulated (QAM) signals at a 1.3 μm wavelength at a 90 Mb/s transmission rate are presented. Two important methods of improving the system performance are discussed and demonstrated: laser intensity noise minimization and error-correction coding using a self-orthogonal convolutional code. The applicability of this transmission technique to the distribution of digital TV services is assessed View full abstract»

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  • Optical interference in subcarrier multiplexed systems with multiple optical carriers

    Publication Year: 1990 , Page(s): 1290 - 1295
    Cited by:  Papers (40)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    It is shown that, when multiple optical carriers are used in a subcarrier multiplexing system, optical interference noise limits the system bandwidth or the number of available channels. Results of a statistical analysis are presented for a system with multilongitudinal mode semiconductor lasers. The results of the statistical calculations indicate that, when one channel per optical source is transmitted, then the system will be limited to only 16 video-quality channels. However, this number can be increased carefully by choosing and maintaining separate wavelengths for the lasers, in order to minimize the interference noise View full abstract»

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  • A new possibility of detecting lightwave signals through IMPATT oscillators

    Publication Year: 1990 , Page(s): 1387 - 1396
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    A novel, yet simple, scheme for detecting intensity-modulated lightwave signals in subcarrier multiplex systems with the help of IMPATT diode oscillators is proposed. The discriminator is seen to exhibit fairly linear characteristics over a moderate band of frequencies. A method of extending the bandwidth without sacrificing the linearity of the system is also suggested. The basic parameters of the system agree closely with the available experimental results View full abstract»

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  • A broad-band distributed-star network using subcarrier fiber transmission

    Publication Year: 1990 , Page(s): 1223 - 1228
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    The development of British Telecom's distributed-star system through the 1980s is described, with particular reference to the development of the optical transmission of video channels. The latest all-fiber network design is detailed, with an explanation of the thinking behind the transmission parameters for the subcarrier scheme adopted. The future policy on modulation techniques is reviewed in light of likely technology and service developments View full abstract»

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  • Erbium-doped fiber amplifier for video distribution networks

    Publication Year: 1990 , Page(s): 1249 - 1256
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    The possibility of an application of Er-doped fiber amplifiers to AM-FDM (frequency division multiplexing) or FM-FDM video distribution networks is discussed. The measured noise and modulation distortion properties of ER-doped fiber amplifiers are good enough to meet even the severe quality standards set for trunk lines. A carrier-to-noise ratio (CNR) of 57 dB for an AM-FDM transmission was measured. A second-order harmonic distortion (HD2) of less than -56 dB was measured by the monotone method (modulation depth m=50%), and a cross modulation distortion (XM) of less than -63 dB was measured by the two-tone method (m=25%×channel). On the basis of these values, composite second-order distortion (CSO) and XM in a 40-channel transmission were estimated as less than -57 dB and -73 dB, respectively. Significant reduction of noise and modulation distortion is made possible by optimizing the length of Er-doped fiber amplifiers and using input- and output-port isolators View full abstract»

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  • Fiber-optic subcarrier multiplexing video transport employing multilevel QAM

    Publication Year: 1990 , Page(s): 1313 - 1319
    Cited by:  Papers (16)  |  Patents (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    The technical feasibility of applying a fiber-optic multilevel QAM (quadrature amplitude modulation) subcarrier multiplexing scheme to a multichannel conventional TV signal transport is explored. This transport scheme has some advantageous features. Because a digital subcarrier modulation scheme is used, a high-quality transmission performance is expected to be achieved, if the bit error is sufficiently small over a transmission line and the required carrier-to-noise ratio (CNR) is relatively small among the many candidates of subcarrier modulation schemes. The use of multilevel modulation allows the bandwidth to be efficiently utilized; consequently, up to 40-channel uncompressed digital TV signals are estimated to be accommodated in the frequency region of the VHF and UHF bands, where well-developed and inexpensive electronics can be easily applied View full abstract»

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  • Design techniques for subcarrier multiplexed broadcast optical networks

    Publication Year: 1990 , Page(s): 1276 - 1284
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    Design techniques which enable the performance of subcarrier multiplexed FM broadcast optical networks to be optimized at the planning stage are described. At the transmitter node, criteria for maximizing the subscriber carrier-to-noise ratio (CNR) are presented. At the subscriber node, it is shown that under the majority of circumstances, the optimum direct detection receiver consists of a low-noise III-V avalanche photodiode and high-impedance front-end preamplifier. Sensitivities approaching -40 dB (1 mW) for 16.5 dB CNR in 36 MHz subscriber bandwidth are predicted for a 60-channel system. Preliminary experimental tests on an optical-feedback subcarrier receiver showed -34 dB (1 mW) sensitivity at 1.55 μm from 16.5 dB CNR in a 36 MHz bandwidth centered on 1.2 GHz with a 12% modulation index single-channel FM test signal View full abstract»

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  • Multichannel AM video transmission using a high-power Nd:YAG laser and linearized external modulator

    Publication Year: 1990 , Page(s): 1369 - 1376
    Cited by:  Papers (36)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    A high-power Nd:YAG laser with a linearized external modulator-based system is demonstrated for a transmission of 50 channels of vestigal sideband amplitude modulated (VSM AM) video. The 1320-nm diode-pumped Nd:YAG laser is an attractive source for AM video transmission due to the high output power (~200 mW) and low relative intensity noise (<-170 dB/Hz). However, the required external modulator generates third-order distortion products, which limit the performance of such a system. A predistortion linearization technique is described. It reduces the modulator generated third-order distortion products by 16.4 dB, allowing a modulation index of 3.37% per channel. When combined with the Nd:YAG laser, this yields a 50-channel video transmission system with a 12 dB optical power budget for video carrier-to-noise ratios of 52 dB and composite distortion products (CSO and CTB) of less than -60 dBc. The demonstrated power budget is sufficient to allow four-way power splitting, with the remaining margin comparable to the test results obtained with DFB (distributed-feedback) laser-based AM transmission systems View full abstract»

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  • Subcarrier multiplexing for lightwave networks and video distribution systems

    Publication Year: 1990 , Page(s): 1240 - 1248
    Cited by:  Papers (118)  |  Patents (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    Applications for subcarrier multiplexing include a variety of analog and digital lightwave transmission systems. An overview of the requirements and capabilities of these systems is presented by describing specific examples of the most popular system types. These examples include multiuser interactive local area networks and multichannel digital, FM, and AM-VSB (vestigal sideband) video distribution systems. Limitations imposed on each by the linearity of directly or externally modulated sources, receiver noise, and relative-intensity noise are discussed View full abstract»

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Aims & Scope

IEEE Journal on Selected Areas in Communications focuses on all telecommunications, including telephone, telegraphy, facsimile, and point-to-point television, by electromagnetic propagation.

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Editor-in-Chief
Muriel Médard
MIT