Analog Transmission Research Articles

Comparison of optimum EDFA designs for in-line amplification in multichannel AM-VSB video lightwave trunking systems

Performance limitations of single- and two-stage EDFAs used as in-line devices in a multichannel hybrid AM-VSB/QAM video lightwave transmission system were studied. It was found that the two-stage EDFA has a much higher saturated NF (>5 dB) compared with the single-stage device when operating at the input signal levels (/spl ges/0 dBm) needed for analog transmission. In the 120-km SMF link with two identical in-line EDFAs, the best-achievable CNR of 50.3-dB was obtained using the single-stage devices, as compared to the CNR of 47.8 dB obtained using the two-stage devices under the same operating conditions. While the optimized two-stage EDFA design provides good performance characteristics as in-line amplifiers for long-haul digital transmission, it is shown experimentally and by simulations that the single-stage design with forward-pumping provides better performance than the two-stage design for in-line amplification in hybrid AM-VSB/QAM video lightwave trunking systems.

Performance of a 16-QAM channel in a hybrid AM-VSB/QAM fiber-optic transmission system based on a subcarrier-multiplexing (SCM) technique

The performance of a hybrid multichannel optical-fiber system for the transmission of analog (AM) and digital (QAM) channels by a subcarrier-multiplexing (SCM) technique is presented. The experimental results are compared with a theoretical model recently proposed that takes into account the clipping effect in semiconductor lasers, which gives rise to an impulsive noise affecting system performance. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 15: 39–43, 1997.

Double-end crosslinked electro-optic polymer modulators with high optical power handling capability

Integrated Mach–Zehnder and straight channel electro-optic modulators have been fabricated with a double-end crosslinked polymer containing amino-sulfone chromophores. The optical power handling capability of these modulators was tested at 1.32 μm wavelength and at input optical power levels compatible with commercial analog transmitters. At a cw peak intensity of 0.9 MW/cm2 inside the waveguide, the double-end crosslinked polymer waveguide modulators exhibited no observable increase in optical loss or degradation of nonlinearity during the experiment period. The poled polymer showed a long-term thermal stability of the electro-optic coefficient at 100 °C and photochemical stability at 633 nm wavelength.

Analog optical transmission of fast photomultiplier pulses over distances of 2 km

New LED transmitters have been used to develop a new method of fast analog transmission of PMT pulses over large distances. The transmitters, consisting basically of InGaAsP LEDs with the maximum emission of light at 1300 nm, allow the transmission of fast photomultiplier pulses over distances of more than 2 km. The shape of the photomultiplier pulses is maintained, with an attenuation less than 1 dB/km. Typical applications of analog optical signal transmission are surface air shower detectors and under water/ice neutrino experiments, which measure fast Cherenkov or scintillator pulses at large detector distances to the central DAQ system.

High-power fibre-coupled 1550 nm DFB laser modulesfor externally-modulated fibre-optic transmission

Singlemode output powers exceeding 165 mW (CW, 25°C) are demonstrated from 1550 nm DFB lasers designed for externally-modulated analogue and digital transmission. The devices have been incorporated into a commercial high-reliability fibre-pigtailed butterfly module which offers output powers up to 40 mW, linewidth < 1 MHz, and RIN < 160 dB/Hz.

Optically linearized modulators: chirp control for low-distortion analog transmission

We show that an increase of composite-second-order (CSO) distortion with increasing fiber length can occur in analog transmission systems using optically linearized Mach-Zehnder modulators and that the degradation is due to generation of chirp in the modulator. We extend a first-principles model to calculate the modulator chirp parameter and show that system CSO calculations using this model are in excellent agreement with measured results. Finally we propose and demonstrate a novel modulator design where chirp is greatly reduced while preserving excellent linearity. For an 80-channel North American frequency plan an optimized low-chirp modulator is predicted to extend the CSO-limited range of the system over standard single-mode fiber from approximately 50 km to greater than 300 km.

Compatibility of FM hybrid in-band on-channel (IBOC) system for digital audio broadcasting

A robust in-band on-channel (IBOC) digital audio broadcast (DAB) system for improved performance over existing FM broadcasting is under development by Westinghouse for USA Digital Radio. Both the analog FM and the DAB signals are transmitted simultaneously in the FM hybrid IBOC system. Broadcasters can simultaneously transmit both analog and digital signals within the allocated channel mask, allowing full compatibility with existing analog receivers. It is shown here that the solution is tolerant of interference from adjacent channels, or interference from the co-channel analog transmission, even in a multiple station, strong-signal urban market. Although the primary focus of this paper is to discuss the compatibility issues between the existing FM and the DAB signals, the paper also briefly describes spectral occupancy, power ratios, modulation formats, and coding, as well as the introduction of frequency and time diversity.

Digital Video and Audio Transmission Alternatives

As television plants convert to serial digital video and digital audio, it becomes apparent that the analog and digital transmission requirements are vastly different. In analog video transmission, it is common to use custom equalizers for long cable lengths, where in digital video transmission, automatic equalization is provided for up to 300 m (1000 ft) of coaxial cable. Where longer transmission paths are required, fiber-optic links offer a better solution. Single-mode fiber-optic transmitters and receivers for serial digital video meeting the proposed SMPTE standards for a serial digital fiber transmission system for ANSI/SMPTE 259M signals' and coaxial cable distribution for AES/EBU digital audio 2 offer several advantages that are described in this paper.

Fabrication and characterization of high-speed polyurethane-disperse red 19 integrated electrooptic modulators for analog system applications

The fabrication and characterization of polymeric electrooptic modulators, made of a thermally crosslinkable polyurethane with Disperse Red 19 side chains, are summarized in this paper. Straight channel and Mach-Zehnder modulators have been fabricated, packaged and tested for the fiber-optic analog transmission system applications. Device performances including halfwave voltage, insertion loss, on-off ratio, and modulation frequency responses were measured. Long-term halfwave voltage stability, dc-bias voltage stability, and optical power handling capability at 1.3-/spl mu/m wavelength were investigated. A carrier-to-noise ratio of 53 dB and 80-channel television transmission have been demonstrated using the packaged polymer modulators.

1.3-μm strained MQW-DFB lasers with extremely low intermodulation distortion for high-speed analog transmission

The intermodulation distortion and the noise characteristics of 1.3-/spl mu/m strained multiquantum-well distributed feedback (MQW-DFB) lasers have been investigated under the modulation frequency of 1.9 GHz in connection with the device structure. In this study, a strained MQW with strain-compensated layers has been introduced in order to increase in the quantum-well number and well width. This causes increase in the differential gain, resulting in increase of the resonance frequency (FR). The FR as high as 5.1 GHz/mW/sup 1/2/ has been obtained which is in good agreement with the theoretical calculation. In addition to the strained MQW structure, a new buried heterostructure entirely grown by MOCVD, named as FSBH (facet selective growth buried heterostructure), has been developed to minimize the leakage current which degrades L-I characteristics at high bias current causing the high distortion. The third-order-intermodulation distortion (IMD3) of -88 dBc and relative intensity noise (RIN) of -152 dB/Hz have been obtained under a two-tone test at 1.9 GHz. This suggests that this newly developed laser is quite suitable for high-speed-subcarrier multiplexing transmission.

Effect of clipping impulsive noise in a hybrid optical-fiber/coaxial network for transmission of subcarrier-multiplexing (SCM) analog and digital channels

In Italy, Telecom Italia has started a plan to develop a broadband network platform that will offer broadcast video, interactive multimedia, and telecommunication services: The SOCRATE project is based on analog and digital channel transmission, the subcarrier multiplexing technique, and hybrid fiber / coaxial architecture. In this article, the effect of clipping impulsive noise is considered in the evaluation of the performance of the analog / digital multichannel transmission system. © 1996 John Wiley & Sons, Inc.

Low-Distortion and High-Output Optical Power Amplifier for Analog Transmission Employing Hybrid Erbium-Doped Fiber Configuration

We have proposed a novel configuration of erbium-doped fiber amplifier (EDFA) which realizes both a flat spectral gain and high output power for analog transmission. This EDFA uses hybrid EDF which consists of serially cascaded EDFs with different glass compositions, based on the fact that EDFs with certain glass compositions exhibit gain tilt of opposite signs in the wavelength range of interest. It is theoretically shown that, in the hybrid EDFA, the gain flattening under any required optical input/output conditions is possible without sacrificing output power by optimizing the constituent EDF lengths. By using thus designed hybrid EDFAs, 50-channel amplitude-modulated vestigial-sideband signals were successfully amplified in four stages with no significant degradation of signal distortions.

Frequency division algorithm for multi-path ghost cancellation

The frequency division algorithm for multi-path ghost cancellation is described through the frequency-domain optimization method for analog and digital TV transmission. Some guidelines for the frequency division method are provided. A novel method to calculate the FIR and IIR coefficients of the deghost systems from the results of the frequency division is proposed. The simulation results are presented by using a Grand Alliance vestigial sideband channel model.

Analogue transmission at 1.55 µm using linearisedelectroabsorption modulator/DFB laser and fibre amplifier

Electrical predistortion is used to linearise an integrated 1.55 µm DFB laser/electroabsorption modulator, yielding a 77-channel CTB of –54.1 dBc and CSO of –61.3 dBc. No significant increase in distortion is measured after Er-doped fibre amplification and propagation through 13 km of non-dispersion-shifted fibre.

Voice communication between humans and machines--an introduction.

Some great pundit once remarked, Every time has its technology, and every technology has its time. Although this is a somewhat simplistic view of technology, it is indeed true that when one thinks of a time period (especially in modern times) one always associates with it the key technologies that revolutionized the way people lived then. For example, key technologies that came of age in the 1970s include the VLSI integrated circuit, the photocopier, the computer terminal, MOS memory, and scanners. In the 1980s we saw the advent and growth of the personal computer, fiber optics, FAX machines, and medical imaging systems of all types. It is not too difficult to predict what some of the key technologies of the 1990s will be; these include voice processing, image processing, wireless communications, and personal information terminals. If we examine the various technologies noted above and look at the interval between the time the technology was and the time the technology began to mature and grow, we see a very complex and intricate relationship. For example, the basic principles of FAX were well understood for more than 150 years. However, until there were established worldwide standards for transmission and reception of FAX documents, the technology remained an intellectual curiosity that was shown and discussed primarily in the research laboratory. Similarly, the concept (and realization) of a videophone was demonstrated at the New York World's Fair in 1964 (so-called Picturephone Service), but the first commercially viable instruments were actually produced and sold in 1992. In this case it took a bandwidth reduction (from 1.5 Mbps down to 19.2 Kbps) and a major cost reduction, as well as algorithm breakthroughs in voice and video coding and in modem design, to achieve this minor miracle. Other technologies were able to leave the research laboratory rather rapidly, sometimes in response to national imperatives (e.g., miniaturization for the space program), and sometimes in response to business necessities. Hence, when fiber optic lines were first mass produced in the 1980s, it was estimated that it would take about two decades to convert the analog transmission facilities of the old Bell System to digital form. In reality the long-distance telephone network was fully digital by the end of 1989, fully 10 plus years before predicted. Similarly, in the case of telephony, it was predicted that it would be about a decade before there would be 1 million phones in use in the United States. By the end of 1992 (i.e., about 8 years after the beginning of the cellular revolution), the 10-millionth phone was already operating in the United States, and the rate of growth of both and wireless telephony was continuing unabated. Now we come to the decade of the 1990s and we have already seen strong evidence that the key technologies that are evolv-

New GMSK transmitter structure for mobile radio systems

Abstract A new parallel transmitter structure is proposed for the gaussian minimum shift keying (GMSK.) modulation scheme. While preserving the same bit error rate performance as existing transmitter configurations, the proposed structure possesses the attractive feature of being highly spectrally efficient. In comparison wilh commercially-available GSM systems, it offers an additional out-of-band attenuation of nearly 15 dB. The performance of the proposed system is investigated under a variety of impairments usually encountered in mobile radio channels, such as noise and fading.

The Japanese scene [digital HDTV

Japan is the only country, so far, to be actually broadcasting high-definition television services. MUSE (multiple sub-Nyquist sampling encoding) is the basis for systems applying bandwidth compression to the transmission of both analog and digital signals. It encodes a signal of 1125 lines and 60 fields per second, a high-definition television (HDTV) signal into an 8-Hz bandwidth. Experimental MUSE broadcasts started in 1990 and have continued ever since. Meanwhile, work has been in progress in areas other than MUSE. Enhanced-definition television, a terrestrial system, is entering its second generation. Integrated digital broadcasting looks to spin many services into a single digital thread for transmission over a single channel. Digital sound broadcasting and hierarchical television transmission will also come in for consideration. The MUSE system depends on digital technology for signal processing, but the HDTV signal that is broadcast is analog, the outcome of frequency modulation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Fabry-Perot laser diode modeling

A model of a single-mode Fabry-Perot semiconductor laser that predicts laser performance in analog transmission has been developed. The model is based on a time domain simulation of the rate equations for a semiconductor laser. The model can be used to simulate laser characteristics such as light versus current, step response, harmonic and intermodulation distortion. Simulated distortion results agree with experimentally measured results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Video bandwidth allocation for multimedia teleconferences

To ensure the quality of a multimedia teleconference, it is essential that sufficient bandwidth be allocated for its use. In this paper a conference traffic model is formulated and link level and conference level congestion measures are derived. Motivated by the advantages of sharing transmission resources in TASI related voice communication systems, an analogous transmission policy for conference videos is proposed. The quantification of conference traffic also enables us to set an admission policy so that the network can accommodate as many conferences as possible without violating conference quality constraints. >

DFB Laser Diodes for Analog Transmission.

DFB laser diodes (LD) have been expected to be attractive light sources for analog transmission, because they have low noise characteristics in radio frequency. However, the early DFB-LD was difficult to apply to practical use because of their large modulation distortion. Main factors of the modulation distortion include 1) intrinsic nonlinear response, 2) spatial hole burning (SHB), and 3) leakage current. This paper reviews technologies of analog DFBLDs focused on the modulation distortion and a device structure to reduce them. CATV system is the most successful analog application for DFB-LDs. In addition, recent progress has been expanding new applications such as a microcellular radio communication. Here, the performance of DFB-LDs for those systems is shown. Furthermore, future trends of analog transmission and what the future analog application requires of DFB-LDs are also described.