Amplitude-modulated Vestigial-sideband Research Articles

Fiber-optic CATV system performance improvement by using split-band technique and photonic crystal fiber

A directly-modulated amplitude modulation-vestigial sideband (AM-VSB) cable television (CATV) erbium-doped fiber amplifier (EDFA)-repeated system that uses split-band technique and photonic crystal fiber (PCF) as a broadband dispersion compensation device is proposed and demonstrated. In contrast to a conventional externally-modulated fiber-optic CATV system, good performance of carrier-to-noise ratio (CNR), composite second order (CSO) and composite triple beat (CTB) were obtained in our proposed systems over a combination of 100-km single-mode fiber (SMF) and 3.6km PCF.

Improved performance of an externally modulated system with external light injection technique

An externally modulated amplitude modulated-vestigial sideband (AM-VSB) CATV erbium-doped fiber amplifier (EDFA)-repeated system that uses external light injection technique is proposed and demonstrated. Good performances of carrier-to-noise ratio, composite second order, and composite triple beat were achieved with 0-dBm light injection over a 100-km single-mode fiber transport.

Bit-error rate of M-QAM signal and its analysis model for composite distortions in AM/QAM hybrid transmission

In cable television (CATV) systems that deliver digital video services by employing a hybrid fiber and coaxial network, it is important to consider digital channel deterioration due to composite distortions, as well as the amplitude-modulation vestigial-sideband channel. Furthermore, it is essential to clearly estimate a digital channel's quality in designing CATV transmission systems. However, there have been few studies on statistical models and an analysis method to estimate the bit-error rate (BER) of M-ary quadrature amplitude-modulation signals for composite distortions. This paper shows statistical properties of composite distortions and a new BER analysis method to handle them. In the evaluations, the amplitude distributions of composite distortions are given by Weibull distributions with skewness levels of 2.3 for composite second-order distortion and 1.5 for composite triple-beat distortion. We propose a new BER analysis method that uses the Weibull distributions for the composite distortion statistical features and demonstrate the effectiveness of the new BER analysis method in estimating BER by comparing its measurement results to calculation results.

37-GHz fiber-wireless system for distribution of broad-band signals

We present a millimeter (mm)-wave fiber-wireless system suitable for the transport and distribution of broad-band signals. We show transmission over fiber and wireless distribution of subcarrier multiplexed amplitude-modulation vestigial-sideband (AM-VSB) video and a digital data stream at 37 GHz using optical carriers generated by a hybrid mode-locked laser (HMLL). We also present a simple model to characterize the effect of fiber chromatic dispersion on the transport of mm-wave modulated signals over fiber, and calculations show that by using an HMLL, broad-band signals can be transported successfully over fiber lengths greater than 150 km using subcarrier frequencies <1 GHz and more than 50 km for subcarrier frequencies <3 GHz.

Optimal predistortion of Gaussian inputs for clipping channels

For a clipped channel with a Gaussian input, a predistortion/restoration technique to reduce clipping-induced nonlinear distortion is proposed and analyzed. The input signal is processed by a nonlinear predistorter circuit, reducing the probability of clipping. The receiver output signal passes through a restorer having an inverse transfer characteristic, which yields the original signal. For both one-sided and two-sided limiter channels, the optimal predistortion curves are determined analytically. A limiter channel with Gaussian input may be used to model clipping-induced nonlinear distortion in optical-fiber common antenna television (CATV) distribution systems using multiple intensity-modulated subcarriers. When applied to an amplitude-modulated vestigial-sideband (AM-VSB) CATV system, the optimal predistortion curves yield sensitivity improvements of 5.3 and 4.4 dB for oneand two-sided limiter channels, respectively.

Amplified Recirculating Delay Lines as Fiber-optic Decoders in TV Systems

A novel approach to decoding chrominance signal in amplitude-modulated vestigial-sideband (AM-VSB) television systems is described. The decoding scheme is achieved by means of amplified recirculating delay lines as fiber-optic filters. The technique is experimentally verified by decoding the chrominance components of the UHF channel 21 of G PAL standard.

Improvements in Carrier-to-Noise-Ratio (CNR) of Lightwave Amplitude Modulated Vestigial-Sideband (AM-VSB) Transmission Systems by the Use of Optical Isolators

In lightwave community antena television (CATV) systems as well as other optical fiber communication networks, a transmitted optical signal is known to be degraded by an intensity noise produced within the fiber due to the interference between the signal and doubly reflected light. We report on the improvements to the signal degradation due to the double Rayleigh backscattering by inserting optical isolators in the trunk lines of the systems. A carrier-to-noise ratio (CNR) has been calculated as a function of the number and the insertion loss of the isolators. The calculated results indicate that there is an optimum number of isolators, and if the insertion loss is less than 0.3 dB, the CNR degradation can be restored by more than 60%. To test the calculated results, we conducted experiments for the specific case of employing one isolator, and obtained good agreements between the two.

Optical fiber amplifiers for optical amplitude‐modulated vestigial sideband transmission systems

AbstractAn optical fiber amplifier for an optical amplitude‐modulated vestigial sideband (AM‐VSB) transmission system has been developed. Various pumping methods in an Er‐doped optical fiber for a high‐power and low‐noise performance are discussed. The bidirectional pumping method was found to be the best. A high‐performance Er‐doped optical fiber has been fabricated, and an optical amplifier has been made with it. The loss budget of 14 dB was obtained in 40‐channel transmission with 51‐dB carrier‐to‐noise ratio (CNR) by using this prototype optical amplifier, which is 6 dB better than before.

Analog video distribution system with three cascaded 980 nm single-pumped EDFA's and 73 dB power budget

A FTTH (fiber to the home)-system for 35 AM-VSB (amplitude modulation vestigial sideband) PAL TV-signals is presented with three cascaded EDFAs (erbium-doped fiber amplifiers) single-pumped with commercially available 980 nm semiconductor laser diodes, with only one optical isolator per amplifier and without any optical filter. This EDFA design leads to an optical distribution system that is cost competitive as compared to coax solutions. The high-optical output power (+13 dBm) in conjunction with the low noise performance (max NF=4.5 dB) allows a 73-dB power budget for a weighted video signal to noise ratio of 45 dB. A high split count of 4*32*64*64=524288 subscribers is realized.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Brillouin scattering in externally modulated lightwave AM-VSB CATV transmission systems

The authors measure the stimulated Brillouin scattering threshold for a CW (continuous wave) laser externally modulated with an AM-VSB (amplitude modulation vestigial sideband) CATV (cable television) signal. The threshold is essentially unchanged from the unmodulated case. For injected powers above the threshold power, substantial degradation of the carrier to noise ratio is seen. >

Optimized performance of erbium-doped fiber amplifiers in subcarrier multiplexed lightwave AM-VSB CATV systems

The authors study the effects of noise when erbium-doped fiber amplifiers are used as signal boosters for signal distribution in amplitude modulation, vestigial-sideband (AM-VSB) subcarrier multiplexed lightwave cable television (CATV) systems. A procedure for finding the amplifier length required to achieve a desired carrier-to-noise ratio at the receiver, while maximizing the allowed post-amplifier splitting ratios and transmission losses has been developed. A simple and easy-to-use approach that circumvents the computationally intensive optimization procedure and allows the design of systems whose performance is very close to optimal is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multiple-reflection-induced intensity noise studies in a lightwave system for multichannel AM-VSB television signal distribution

In a lightwave system used for transmission and distribution of multichannel AM-VSB (amplitude-modulated vestigial side-band) television signals, the dependence of multiple-reflection-induced intensity noise on laser diode linewidth, fiber jumper length, modulation index, and the number of connectors is studied. The noise is investigated for systems both with and without optical amplifiers. The requirements on the reflectance of fiber connectors/splices, the maximum number of connectors, and the usable optical amplifier gain are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Applications of traveling-wave laser amplifiers in subcarrier multiplexed lightwave systems

Describes applications of traveling-wave laser amplifiers (TWLAs) in subcarrier-multiplexed distribution systems for both frequency-modulated (FM) and amplitude-modulated vestigial-sideband (AM-VSB) video signal distribution. The characteristics of a 1300-nm facet-angled and antireflection-coated TWLA are described. Analytical carrier-to-noise ratio (CNR) characterizations of subcarrier-multiplexed systems employing TWLAs are given. Experimental results of using TWLAs in multichannel FM and AM-VSB video signal systems are described. The potential optical-reflection problems associated with the residual reflectivities of optical fiber connectors and splices while using TWLAs are briefly described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>