Vestigial Sideband Research Articles

Optical performance monitoring using narrowband radio-frequency analysis at the half-clock frequency

Feature Issue on Optical Performance Monitoring (OPM). A new technique for monitoring the signal-to-noise ratio (SNR) of a randomly modulated optical data signal is proposed and demonstrated. The signal is detected and then subjected to a narrowband rf demodulation at precisely half the data clock frequency. Because of symmetries present in the modulation spectrum at the half-clock frequency, the demodulated signal is confined to a single dimension in the recovered phase space. In contrast, the noise power is distributed isotropically within the phase space, and the SNR is measured by taking the ratio of the power recovered along the signal dimension to the power recovered along the orthogonal dimension. The narrowband nature of the measurement makes it highly sensitive. The technique is demonstrated for return-to-zero modulated data at 10 Gbits/s, where it accurately tracks OSNR variations from 10 to 26 dB with only -24 dBm of optical input. The measurement is also shown to be sensitive to chromatic dispersion and can be made to track OSNR variations in the presence of large amounts of chromatic dispersion with vestigial sideband optical filtering. These properties make this technique an ideal candidate for optical performance monitoring in transparent optical networks, where a sensitive, low-cost monitoring solution is needed for effective fault localization.

Multicarrier modulation with blind detection capability using cosine modulated filter banks

The cosine modulated filter bank (CMFB) is introduced as a multicarrier modulation (MCM) technique for wideband data transmission over wireless channels. Under the name discrete wavelet multitone modulation, CMFB has been considered for data transmission over digital subscriber lines. We propose a new receiver structure that is different from those proposed previously. The new structure simplifies the task of channel equalization, by reducing the number of equalizer parameters significantly. We also propose a novel blind equalization algorithm that fits very nicely in the proposed structure. Moreover, we discuss the bandwidth efficiency of the proposed CMFB-MCM system and show that it is superior to the conventional (single carrier) quadrature amplitude modulation (QAM) and orthogonal frequency-division multiplexing (OFDM). The CMFB is found to be a signal processing block that stacks a number of vestigial sideband modulated signals in a number of overlapping subchannels in the most efficient way. The proposed CMFB-MCM is also compared to OFDM with respect to bit-error rate performance. Under the conditions that the channel impulse response duration remains less than the length of cyclic prefix, OFDM is found marginally superior to CMFB-MCM. However, OFDM degrades very fast when the channel impulse response duration exceeds the length of the cyclic prefix. CMFB-MCM, on the other hand, is found less sensitive to variations in channel impulse response duration.

Countermeasures of Stimulated-Raman-Scattering-Induced Video Distortion in 1.65 µm Optical Time-domain Reflectometer On-line Monitoring 1.55 µm Cable Television System

The countermeasures of stimulated-Raman-scattering (SRS)-induced baseband video distortion in the 1.65 µm optical time-domain reflectometer (OTDR) on-line monitoring 1.55 µm amplitude modulation with vestigial sideband (AM-VSB) cable television (CATV) transmission system are investigated theoretically and experimentally. The countermeasures entail the reduction in the optical modulation index (OMI) of the AM transmitter, OTDR peak power and/or pulse width. The results of numerical simulations and experimental measurements are in good agreement. Moreover, the countermeasure for eliminating the SRS-induced baseband video distortion by the 1.31 µm OTDR on-line monitoring technique is investigated and demonstrated.

Fiber optical CATV system-performance improvement by using external light-injection technique

A directly modulated amplitude modulation with vestigial sideband cable television (CATV) erbium-doped fiber amplifier-repeated system that uses an external light-injection technique is proposed and demonstrated. The external light-injection technique greatly enhances the frequency response of the laser diode, and thus improves the overall performance of the fiber optical CATV system.

Mathematical Modeling of VSB-Based Digital Television Systems

We mathematically analyze the passband vestigial sideband (VSB) system for the Advanced Television Systems Committee (ATSC) digital television standard and present a baseband-equivalent VSB model. The obtained baseband VSB model is represented by convolution of the transmission signal (before modulation) and the baseband equivalent of the complex VSB channel. Due to the operation of the physical channel as an RF passband and the asymmetrical property of VSB modulation, it is necessary to use a complex model. However, the passband channel may be reduced to an equivalent baseband. We show how to apply standard channel model information such as delay, gain, and phase for multiple signal paths to compute both the channel frequency response with a given carrier frequency and the resulting demodulated impulse response. Simulation results illustrate that the baseband VSB model is equivalent to the passband VSB model.

Optically preamplified receiver performance due to VSB filtering for 40-Gb/s optical signals modulated with various formats

Optically preamplified receiver performance according to the vestigial sideband (VSB) filtering has been numerically investigated for 40-Gb/s optical signals modulated with nonreturn-to-zero, duobinary nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed RZ, and duobinary carrier-suppressed RZ formats. The VSB filtering enables the spectral widths of NRZ, duobinary NRZ, and RZ signals to be reduced without severe power penalties at the receiver. On the other hand, carrier-suppressed RZ and duobinary carrier-suppressed RZ signals have no large advantages over VSB filtering because of the characteristics of their signals. Our results suggest that RZ signals are the most suitable modulation format for VSB filtering, without considering the filter loss, because of the tolerance of the intersymbol interference and a large spectral width. However, duobinary NRZ signals are the most suitable modulation format for VSB filtering, considering the filter loss, because of their narrow spectral width.

0.8 bit∕s∕Hz spectral efficiency at 10 Gbit∕s via vestigial-sideband filtering

The first 10 Gbit/s DWDM transmission at 12.5 GHz spacing without polarisation division multiplexing or polarisation interleaving is demonstrated. This dense channel spacing is accomplished via vestigial sideband filtering and 8×10 Gbit/s has been transmitted over 200 km of SMF-28 fibre.

Chromatic dispersion monitoring technique using sideband optical filtering and clock phase-shift detection

We propose and demonstrate a novel technique for 40- and 10-Gb/s chromatic dispersion monitoring that uses an optical filter to select the upper and lower vestigial-sideband (VSB) signals in the transmitted optical data and determine the relative clock phase shift caused by dispersion. Without modification of transmitters, this technique provides low cost chromatic dispersion monitoring for WDM systems, <3 ps/nm dispersion resolution for 40-Gb/s data, and greatly reduced sensitivity to the influence of polarization mode dispersion.

Spectrally efficient multiplexing of O-QPSK or VSB signals using wavelet packet-based filter banks

This paper presents fundamental principles for the design of a data transmission scheme that obtains spectrally efficient orthogonal frequency division multiplexing of digital vestigial sideband (VSB) signals. Real binary input data streams are fed into a synthesis filter bank from wavelet packet theory. Mobile satellite and personal communications applications are considered. Desirable properties of this approach are identified and discussed. A new proof of the equivalence between digital vestigial sideband and OQPSK is derived that enables convenient use of real binary signal inputs and descriptions in terms of VSB concepts. Two new closely related digital filters are added at the roots of two identical trees to obtain VSB multiplexer channels that are closely packed in frequency. Frequency and time resolution from multiresolution theory are related to bandwidth concepts. It is shown how bandwidth on demand by factors of 2 can be obtained.

Enhanced VSB system

Enhancements to the existing ATSC (Advanced Television Systems Committee) VSB (vestigial sideband) digital television standard (A/53) were developed independently at the authors' companies. Each company's private tests showed its system to be backward compatible with existing ATSC receivers and to offer improvements in flexibility and signal robustness to meet broadcasters' needs. When both systems were submitted to the ATSC committee on enhancements, the two companies found their proposals to be very complementary, resulting in the formation of a joint proposal for enhancement of the VSB digital TV broadcasting system. The combined proposal is described along with its technical benefits.

Hybrid 10-Gb/s, 2.5-Gb/s, 64-QAM, and AM-VSB high-capacity wavelength-division-multiplexing transport systems using SMF and LEAF fibers

A four-wavelength high-capacity hybrid wavelength-division-multiplexing (WDM) system separately over 100-km standard single-mode fiber and nonzero dispersion-shifted fiber of large effective area fiber is demonstrated. The WDM wavelengths contain one 10-Gb/s signal, one 2.5-Gb/s signal, one 64-quadrature amplitude modulator signal of 110 channels, and one amplitude module with vestigial sideband signal of 80 channels. Satisfaction of a huge variety of receiving requirements and reduction of fiber nonlinearities-induced degradations by controlling channel powers are also considered. Such a hybrid WDM system would be attractive for multiservice trunk applications in advanced transport systems for providing both CATV and telecommunication services.

Design method for FIR-based Hilbert transform filters suitable for broadband AM-SSB

A new synthesis approach to the design of finite impulse response (FIR) filters with a close approximation to the Hilbert transform for AM-SSB generation of wideband signals is discussed. It is shown that the new method can reduce the vestigial sideband by up to 59% compared with that obtained with a conventional FIR filter design method.

2 Tbit∕s (200×10 Gbit∕s) over 9240 km transmission experiment with 0.15 nm channel spacing using VSB format

2 Tbit/s (200 WDM/spl times/10 Gbit/s) transmission over 9240 km using only a C-band erbium-doped fibre amplifier is demonstrated. A vestigial sideband modulation scheme was adopted to realise 0.15 nm channel separation. Ultra-high spectral efficiency of 53% was achieved. All channels showed better than 9 dB Q-factor, which can be corrected to less than 10/sup -9/ BER after OSW Super forward error correction.

Vestigial sideband filtering at 10 Gbit∕s using 12.5 GHz channel-spacing demux

A 32-channel 12.5 GHz-spaced free-space demux with low crosstalk and low polarisation dependent loss has been constructed. Using this demux, vestigial sideband filtering at 10 Gbit/s has been studied. It is shown that this demux can achieve very high spectral efficiency without polarisation division multiplexing.

10 Gbit/s 177 km transmission over conventional singlemode fibre using a vestigial side-band modulation format

The transmission of 10 Gbit/s vestigial-side-band (VSB) signals over 177 km of conventional singlemode fibre is demonstrated. The dispersion penalty was measured to be &lt; 3 dB. The simulation analysis shows that the small dispersion penalty comes from the combination of reduced spectral width of the VSB signal and the negative dispersion of the VSB filter.

NTSC in-band data broadcasting using orthogonal frequency division multiplexing

This paper presents a new data broadcasting technique for transmitting data using the orthogonal frequency division multiplexing modulation scheme, within the NTSC television signal. The data signal is inserted in the vestigial sideband of the video signal. The advantages of this implementation are that the shape of the data spectrum minimizes the degradation of the picture quality and increases the noise margin of the data signal. Two approaches are taken to evaluate the performance of this system. In the first one, computer simulations are used to determine the available bit rate by varying the number of carriers. Bit error rate measurements are also done to evaluate the performance of the system when the data signal is combined with the NTSC television signal. In the second approach, the perceptual impact is determined, using accepted subjective assessment methodology, when varying levels of OFDM carriers are injected into the NTSC signal. The results show that the proposed system has the potential to offer higher data rate throughput than existing data broadcasting systems, with negligible degradation effects on the NTSC picture quality.

An adaptive pre-distorter for the compensation of HPA nonlinearity

A high power amplifier (HPA) is used for the amplification of transmitting communication signals. However, it produces distortions by creating AM/AM and AM/PM modulations in the transmitting signal, Accordingly, this nonlinearity results in bandwidth expansion and nonlinear distortion in the in-band signal. This paper proposes an algorithm for the operation of a pre-distorter, which is composed of a look-up table (LUT), that can compensate for the distortion produced by an HPA. For the fast initialization of the LUT, an estimation algorithm is also proposed for the HPA characteristics. Furthermore, an adaptive algorithm based on the minimization of the mean square error is proposed to compensate for the time-varying property of an HPA. The performance of the proposed algorithm is analyzed by applying the algorithm to an 8-level vestigial sideband (VSB) modulation to be used in the ATSC terrestrial digital TV system.

8-VSB channel coding analysis for DTV broadcast

This article analyzes channel coding and equalization stages in the 8-level vestigial sideband transmission for the digital television broadcast system developed by ATSC, the Advanced Television Systems Committee. We present bit error rate versus C/N performance for a simulator developed by the authors for the purpose of assessing the robustness of the ATSC 8-VSB coding and equalization stages in the presence of multipath propagation, additive Gaussian noise and of channel impulsive noise surges. Implementation aspects for the developed simulator are discussed.

A design of VSB receiver IC for digital television

This paper describes a single ASIC chip that demodulates and decodes vestigial side band (VSB) digital TV signals. The VSB IC has been implemented for the receiver based on the ATSC digital TV standard. It features fast digital carrier recovery and robust channel equalization. The IC is fabricated with 0.35 /spl mu/m CMOS technology with 3 metal layers. It can be applied to both modes of signal reception -8 VSB for terrestrial broadcast and 16 VSB for cable transmission.

Preliminary DTV field test results and their effects on VSB receiver design

The Federal Communication Commission (FCC) has selected the Advanced Television System Committee (ATSC) digital television (DTV) standard (except for video formats) as the new terrestrial standard for the United States. The U.S. has begun the transition from the 50+-year old analog NTSC system to the new digital ATSC system. A brief overview of ATSC's digital vestigial sideband (VSB) transmission system is covered, as well as the methodology used in field-test data gathering and data analysis. Results from DTV field tests in several U.S. cities by early adopter DTV broadcasters are summarized. Finally, FCC planning factors for consumer DTV receivers that are used in allocating spectrum for the 1600+ broadcast stations based on NTSC replication are discussed along with digital VSB receiver target design parameters that were developed as a result of these VSB field tests.