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Lightwave Technology, Journal of

Issue 1 • Date Jan 1993

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Displaying Results 1 - 20 of 20
  • Optical coherent broad-band transmission for long-haul and distribution systems using subcarrier multiplexing

    Publication Year: 1993 , Page(s): 116 - 127
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1012 KB)  

    Signal multiplexing techniques for coherent optical transmission are compared, and appropriate application for a coherent subcarrier multiplexing (SCM) system is discussed. Optical frequency modulation (FM) using direct modulation of a distributed-feedback laser diode (DFB-LD) and a heterodyne detection is shown to be feasible. A transmission system using a local laser in the transmitter is unaffected by polarization and is cost effective. Phase noise can be suppressed by a phase-noise-canceling circuit (PNC) in a heterodyne receiver. This circuit can also effectively compensate for the frequency of instability of light sources. A theoretical simulation of a coherent SCM system showed that 100 channels of 30-MHz FM signal or 15 channels of 155-Mb/s signal can be distributed to 10000 subscribers using single-stage or double-stage optical amplifiers View full abstract»

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  • Progress in externally modulated AM CATV transmission systems

    Publication Year: 1993 , Page(s): 82 - 105
    Cited by:  Papers (53)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2016 KB)  

    Recent advances in electronic linearization of AM CATV transmitters based on externally modulated diode pumped Nd:YAG lasers are presented. The theoretical principles and practical issues related to the methods of feedforward and predistortion linearization, the factors affecting system performance and the emerging devices, circuits, subsystems, and systems architectures are reviewed. In experiments based on a predistortion linearized system, transmission over two fibers of 30 km each, wherein each fiber carries 80 NTSC channels, is now routinely achieved with a CNR>50 dBc, a CTB<-65 dBc, and a CSO of typically -70 dBc. As the number of channels broadcast over each fiber is reduced from 80 to 60, CNR increases to 52 dBc. The fiber links served by the system under test each have 12-dB link budget, and include four connectors per fiber, with no degradation observed in one link when the connectors were opened on the other link View full abstract»

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  • Analysis and design for optical video transport distribution system with video on demand service

    Publication Year: 1993 , Page(s): 106 - 115
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (852 KB)  

    A cost-effective methods of multiplexing, transmitting, and selecting optical video signals is proposed and demonstrated by using appropriate combinations of bidirectional optical trunk-amplifier, medium-density wavelength division multiplexing (WDM) and optical space switching techniques for rapid cost-effective construction. The major factors affecting optical video transport/distribution system design are described. In particular, a tapping-type optical loop-shaped trunk section network is proposed from the viewpoint of system reliability, probability of call-loss, and B-ISDN with analog overlay. The experimental results and design philosophy for an optical selector composed of WDM filters and space switches connected by silica-based waveguide on a chip are also discussed View full abstract»

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  • Intermodulation distortion in high dynamic range microwave fiber-optic links with linearized modulators

    Publication Year: 1993 , Page(s): 3 - 6
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    Linearization of integrated optic intensity modulators significantly reduces the two-tone intermodulation distortion. The resulting intermodulation distortion produced by these modulators then varies as the input power to the fifth-order link system, the overall intermodulation product is a combination of third-order and higher-order terms. The authors determine the dynamic range of a cascaded microwave network consisting of a preamplifier, a high-dynamic-range fiber-optic link with a highly linear modulator, and a postamplifier. An expression is found that relates the intermodulation power at the output to the relative suppression from the signal level. As an example, a hypothetical 10-GHz low-distortion fiber-optic link that has a dynamic range of 125 dB in a bandwidth of 1 Hz is cascaded with various preamplifiers, and it is shown that the dynamic range of the system is reduced by as much as 20 dB, depending on the third-order intercept of the amplifier View full abstract»

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  • Optimization of fiber amplifier SCM lightwave video systems using direct and external modulation

    Publication Year: 1993 , Page(s): 76 - 81
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    An analysis of the design factors involved in optimizing laser transmitters for SCM video distribution networks is presented. This includes optimization of the erbium-doped amplifier, linearized external modulation, and laser overmodulation to increase the optical loss budget. A full nonlinear distortion spectral analysis is employed to determine the dependence of the optimum optical modulation index on the allowable postamplifier loss. A general optimization procedure has been developed for the fiber amplifier and modulator to maximize the postamplifier loss for a specified CNR objective. Results are presented showing a comparison between the distribution capacity of direct and externally modulated SCM-EDFA systems for VSB-AM and FM-SCM transmission systems View full abstract»

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  • All-fiber video distribution (AFVD) systems using SCM and EDFA techniques

    Publication Year: 1993 , Page(s): 128 - 137
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (876 KB)  

    The authors describe the design and performance of all-fiber video distribution (AFVD) systems based on AM/FM FDM subcarrier multiplexing (SCM) and erbium-doped fiber amplifiers (EDFAs). The impact of applying EDFAs to SCM analog video distribution systems is investigated. AM/FM hybrid systems, which can simultaneously distribute 11 AM TV channels and 50 FM TV channels are proposed and discussed. Four-stage amplifier-branch transmission experiments are introduced. The construction and performance of a newly designed 50-channel FM tuner are also presented View full abstract»

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  • Fundamental nonlinear distortions in analog links with fiber amplifiers

    Publication Year: 1993 , Page(s): 7 - 15
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (868 KB)  

    The author analyzes the second-order distortion in a modulated laser-based AM subcarrier multiplexed (AM-SCM) video transport system using fiber amplifiers for power boosting. All three of the involved system elements: the laser, the fiber amplifier, and the transmission fiber, contribute to the system distortion. The laser distortion originates from the internal photon-electron interaction, whereas the fiber amplifier and dispersive distortion are directly related to the intrinsic frequency chirping of the modulated laser. From the distortion magnitude and phase analysis, the author finds that under most situations the distortions have an electronic counterpart and can be electronically compensated. In addition, the system distortion can be minimized with a combination of critically chosen elements that have minimum or counteracting distortion mechanisms. Optically amplified AM-SCM systems can thus be engineered to perform well within the stringent distortion requirements for both 1.3- and 1.55-μm wavelength ranges View full abstract»

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  • Clipping distortion in lightwave CATV systems: models, simulations, and measurements

    Publication Year: 1993 , Page(s): 138 - 146
    Cited by:  Papers (37)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    Theoretical, numerical, and experimental investigations of clipping distortions in CATV systems are reported. The applicability of A.A.M. Saleh's (1989) calculation of the carrier-to-nonlinear-distortion ratio (CNLD) is extended by incorporating a more precise spectral analysis and further analytic results. An effective transfer function model which spectrally resolves the clipping distortion at intermodulation products (IMPs) of all orders and frequencies, and features closed-form analytic calculation of the second- and third-order distortions (CSO and CTB) from basic principles, as well as the CNLD, is introduced. It is found that Saleh's model slightly overestimates the simulation results for the CNLD, while the new model is in essential agreement with the simulation for all three distortion measures. Experimental measurements of the CSO, CTB, and CNLD over a 50-dB range in distortion exhibited excellent agreement with the simulations and the new model over the entire range. The unified nature of the model allows standard CATV, CSO, and CTB measurements to be theoretically connected to the CNLD and clipping boundary View full abstract»

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  • Fiber-optic digital video multiplexing using optical CDMA

    Publication Year: 1993 , Page(s): 20 - 26
    Cited by:  Papers (35)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    The use of laser pulsing in the form of code-division multiple access (CDMA) to multiplex a set of digital video signals over a fiber network is proposed. The laser pulsing is used to generate unique code sequence addresses which identify each source, and the video data are modulated on these sequences. Digital encoding using pulse position modulation (PPM) is proposed, having advantages that permit efficient integration of optical and electronic processing. Data recovery is achieved by optical correlation for sequence recognition, followed by standard electronic PPM decoding. The relation between key system parameters of the encoding, decoding, and optics is derived, and indicates that compressed video rates between 5 and 20 Mb/s/channel, with 25-50 channels, is possible with relatively standard hardware. Experimental breadboard results being carried out at USC on this system indicate the feasibility of the CDMA concept for fiber multiplexing View full abstract»

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  • Fundamental limitations in EDFA-based subcarrier-multiplexed AM-VSB CATV systems

    Publication Year: 1993 , Page(s): 42 - 48
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    The authors present and discuss fundamental limitations for erbium-doped fiber amplifier (EDFA)-based subcarrier-multiplexed AM-VSB CATV distribution systems. The impairments they consider are shot noise, amplifier spontaneous emission noise, and laser clipping-induced nonlinear distortion. Treating the amplifier input signal power and pump power as resources, they obtain limits on the number of receivers to which one can deliver, say, 60 (or 80) channels at a carrier-to-noise ratio (CNR) of 55 dB (or 48 dB). A simple approach that can be used to recalculate the results presented here for different system and amplifier fiber parameters is presented View full abstract»

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  • Subcarrier multiplexed broad-band service network: a flexible platform for broad-band subscriber services

    Publication Year: 1993 , Page(s): 60 - 69
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (964 KB)  

    The concept of the subcarrier multiplexed broadband service network (SCM-BSN) has been developed in response to the need to provide low-cost integrated broadband services in the local loop. The SCM-BSN architecture incorporates three elements which have been identified over the past few years as key cost-saving features: passive optical splitting, fiber-to-the-curb, and subcarrier multiplexing of video signals. The SCM-BSN concept, a prototype system that has been built at the GTE Laboratories, and some possible evolutionary scenarios to integrated digital services are described View full abstract»

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  • Influence of the carrier density dependence of the absorption on the harmonic distortion in semiconductor lasers

    Publication Year: 1993 , Page(s): 16 - 19
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    It is shown that the carrier density dependence of the absorption can result in a significant increase of the harmonic distortion caused by gain suppression or by spatial hole burning in distributed-feedback (DFB)-lasers. This carrier density dependence of the absorption is often neglected in theoretical studies, but the author found that it may result in a dominant contribution to the second-order distortion in the AM response, especially at high output powers. The distortion then mainly depends on material parameters such as differential gain, differential absorption and the gain suppression method View full abstract»

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  • The use of fiber optics in cable communications networks

    Publication Year: 1993 , Page(s): 154 - 166
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1168 KB)  

    The authors discuss past, present, and future use of fiber optics and optoelectronics, in conjunction with coaxial communications networks, to provide enhanced communications and networking capabilities. The role of network architectures and various options regarding wavelengths and modulation techniques are discussed and compared, as are several scenarios of fiber to the neighborhood, service area, curb, and home View full abstract»

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  • Implementation and evaluation of a dual parallel linearization system for AM-SCM video transmission

    Publication Year: 1993 , Page(s): 34 - 41
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (652 KB)  

    An externally modulated transmitter was linearized for AM subcarrier multiplexing (AM-SCM) video transmission. Linearization was accomplished by combining the outputs of two lithium niobate Mach-Zehnder interferometers which were simultaneously modulated. By controlling the optical and RF power at each modulator, more than 20 dB of third-order distortion cancellation was demonstrated for a multitone video spectrum. Results are presented for both NTSC and PAL B/G frequency plans. The effects of modulator nonideality on system performance are analyzed and confirmed experimentally. In particular, overall system performance is shown to be very sensitive to acoustic effects and to optical and electrical multipath interference. System modeling is used to provide tolerances on various critical parameters View full abstract»

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  • Optimum range for DFB laser chirp for fiber-optic AM video transmission

    Publication Year: 1993 , Page(s): 55 - 59
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Simple expressions for the impact of the distributed feedback (DFB) laser chirp on the system noise and distortion specifications of AM CATV fiber links are derived. These· expressions are found to agree well with measured results. There is a narrow range of chirp for which the degradation of both noise and distortion is low. 1310-nm lasers are found to have chirp within the acceptable range. 1550-nm lasers are found to have chirp that is unacceptably large for most CATV applications View full abstract»

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  • Semiconductor pump laser technology

    Publication Year: 1993 , Page(s): 167 - 175
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    Recent progress in high-power semiconductor lasers for erbium-doped fiber amplifiers is described, focusing on 1.48-μm InGaAsP/InP lasers and 0.98-μm InGaAs/GaAs lasers. The experimental output powers exceed 200 mW (the maximum power was 325 mW) for 1.48-μm lasers, and simulation results indicate that over 400 mW could be obtained by optimizing parameters in strained-layer (SL) multiple-quantum-well (MQW) lasers. Stable operation over a few thousand hours under 100-mW power is demonstrated for liquid-phase-epitaxy-grown lasers, MQW lasers, and SL-MQW lasers grown by all-metal organic vapor-phase epitaxy (MOVPE). For 0.98-μm lasers, improvement in the fiber coupling efficiencies and long-term reliabilities are described. Their power coupled into a single-mode fiber has reached over 100 mW, with coupling efficiencies of approximately 40%. Although reliability seems to be one of the drawbacks compared with 1.48-μm lasers, stable operation for over 10,000 h at 50°C and 30 mW has been reported View full abstract»

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  • Transmission characteristics of DFB laser modules for analog applications

    Publication Year: 1993 , Page(s): 147 - 153
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    Analog transmission characteristics of highly linear 1.3- and 1.55-μm distributed feedback (DFB) laser modules are described. To obtain high-power and high-performance DFB lasers, the bias dependence of distortion characteristics is discussed. The carrier-to-noise ratio, the composite second-order distortion, and the composite triple beat of the DFB laser module which is developed for analog CATV applications are presented. The analog transmission characteristics, such as CNR degradation, after fiber transmission, dispersion-induced distortion, and the influence of reflection, have been made clear. The stable high linearity of the DFB laser also has been confirmed by the composite distortion measurement under an accelerated aging test View full abstract»

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  • Solid-state laser pumping of 1.5-μm optical amplifiers and sources for lightwave video transmission

    Publication Year: 1993 , Page(s): 27 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    An optical power amplifier and a laser source are demonstrated at 1.5 μm. A diode-pumped Nd:YAG laser is used as the pumping source for an Er/Yb co-doped gain medium. The power scaling advantages of this approach are demonstrated. Up to +21 dBm of output power is obtained from the Er/Yb amplifier and up to +19 dBm is obtained from the laser source. The Er/Yb power amplifier was deployed in a 42-channel AM link with 40 km of fiber, and an optical loss budget of 18 dBm was demonstrated View full abstract»

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  • A new compound modulation technique for multichannel analog video transmission on fiber

    Publication Year: 1993 , Page(s): 49 - 54
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    An analog transmission technique for multichannel TV transmission on fiber using frequency-modulated/time-division multiplexing (FM/TDM) is described and compared with present digital and analog systems. Analysis and simulations indicate that the proposed system has a very low sensitivity to nonlinearities, similar to digital systems, and much better than current frequency-modulated/frequency-division multiplexed (FM/FDM) systems. This permits the use of higher optical modulation depth (as high as digital systems), which results in achieving high signal-to-noise ratio, large power budget, and/or the use of lower cost optical components. Furthermore, a better spectrum efficiency is possible View full abstract»

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  • Digital video compression-an overview

    Publication Year: 1993 , Page(s): 70 - 75
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    Some of the more commonly used video compression schemes are reviewed. They are differential pulse code modulation (DPCM), Huffman coding, transform coding, vector quantization (VQ), and subband coding. The use of motion compensation to improve compression is also discussed View full abstract»

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Aims & Scope

The Journal of Lightwave Technology contains articles on current research, applications and methods used in lightwave technology and fiber optics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs