Spectral predictions for pulse interval and width modulation

An expression for the frequency spectrum of pulse interval and width modulation (PIWM) is presented. Experimental results obtained have shown close agreement with spectral predictions from the formula. Performance figures are also included from a practical PIWM optical-fibre transmission system intended for use with TV and video signals.<>     

Bidirectional Wavelength Reconfigurable Module Based on Tunable Fiber Bragg Grating and Remote Pump Amplifier

Abstract

This article presents a novel bidirectional wavelength reconfigurable optical network utilizing a remotely pumped erbium-doped fiber amplifier and tunable fiber Bragg gratings. The system is experimentally demonstrated at a 10-Gb/s per channel over 20-km fiber span that verifies the metro-network range system performance. The achieved power penalty is less than 1 dB when compared to the back-to-back transmission link. An example of practical application where the proposed module is used as an add/drop multiplexer and a remote node in the bidirectional wavelength division multiplexing passive optical network system is described.     

Performance characteristics of cascaded delay‐line node architectures in single‐path interconnection networks

Internally buffered multistage interconnection network architectures have been widely used in parallel computer systems and large switching fabrics. Migration from electrical domain to optical domain has raised the necessity of developing node architectures with optical buffers. Cascaded fibre delay line architectures can be seen as possible realizations of output and shared buffering in a 2 × 2‐switching element. These approaches can be used as buffered node architecture in a Banyan like interconnect. In this paper, we investigate and compare these approaches by using simulation methods. Different performance metrics, such as normalized throughput, average packet delay, packet loss rate and buffer utilization have been used under uniform and non‐uniform traffic models. Results show that the TC‐chain node Banyan network offer an improved normalized throughput and average packet delay performances under both traffic models without disrupting first‐in‐first‐out order of arrivals. The switched delay‐line requires fewer switching elements than TC and TTC architectures but at the cost of high packet delay. Copyright © 2004 John Wiley & Sons, Ltd.     

Differential phase error in pulse-width-modulated TV transmission systems

A simple method is presented for prediction of the lower limit of differential phase error in TV transmission systems employing pulse width modulation (PWM). Comparison with measured data over a range of modulation indices demonstrates very close agreement.     

Spectral predictions for hybrid pulse frequency and widthmodulation

An expression for the modulation spectrum of the recently developed hybrid pulse frequency and width modulation technique (PFWM) is presented. Spectral predictions obtained from the formula show close agreement with experimental results obtained from a practical PFWM optical-fibre transmission system     

BPSK Subcarrier Intensity Modulated Free-Space Optical Communications in Atmospheric Turbulence

Free-space optical communications (FSO) propagated over a clear atmosphere suffers from irradiance fluctuation caused by small but random atmospheric temperature fluctuations. This results in decreased signal-to-noise ratio (SNR) and consequently impaired performance. In this paper, the error performance of the FSO using a subcarrier intensity modulation (SIM) based on a binary phase shift keying (BPSK) scheme in a clear but turbulent atmosphere is presented. To evaluate the system error performance in turbulence regimes from weak to strong, the probability density function (pdf) of the received irradiance after traversing the atmosphere is modelled using the gamma-gamma distribution while the negative exponential distribution is used to model turbulence in the saturation region and beyond. The effect of turbulence induced irradiance fluctuation is mitigated using spatial diversity at the receiver. With reference to the single photodetector case, up to 12 dB gain in the electrical SNR is predicted with two direct detection PIN photodetectors in strong atmospheric turbulence.     

Bit-error-rate analysis for a 100-Gbit/s nonlinear optical loop mirror demultiplexer employing soliton control and signal pulses

On the basis of a previously derived mathematical model, the power penalty associated with a nonlinear optical loop mirror (NOLM) demultiplexer was calculated, with timing jitter noise, bit-to-bit cross talk, and channel cross talk taken into consideration. Simulation results show that a 3-dBm improvement in the receiver sensitivity at a bit error rate of 10(-9) can be achieved by choice of the appropriate walk-off time between the control and the signal pulses within the NOLM demultiplexer.     

Noise performance of the pulse slope modulation system

A simple formula for the signal-to-noise ratio (SNR) at the output of the pulse slope modulation system is derived. The predicted SNR performance is compared with measured data obtained from a hardware model of the system. Practical results are in good agreement with predictions.<>     

Spectral structure of multitone pulse width modulation

The multiple sidetone structure recently reported in pulse width modulation arising from multitone inputs can now be accurately predicted by a newly derived modulation formula. Excellent agreement is demonstrated between measurements and theoretical calculations.<>     

A feature extraction and pattern recognition receiver employing wavelet analysis and artificial intelligence for signal detection in diffuse optical wireless communications

Optical wireless diffuse indoor infrared communication systems have as yet large unrealized bandwidths that are not subject to the same regulatory control as radio frequency systems. Usually, well established RF techniques are used to combat channel imperfections for IR implementations. Here, we introduce a novel receiver system based on the multiresolution time-frequency feature extraction capabilities of wavelet analysis, coupled with the well recognized pattern recognition performance of artificial neural networks for mitigating the effects of bandwidth limiting channel-induced distortion.