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Journal ArticleDOI

Optimistation of the Bias of an Injection Laser in a Digital Fibre Optic Communication System

01 Jul 1986-Iete Journal of Research (Taylor & Francis)-Vol. 32, Iss: 4, pp 343-345
TL;DR: In this paper, the effects of lasing time delay of injection laser diodes in digital fiber optic communication systems are considered and the solution of applying a constant dc bias is considered taking into account the resulting non-zero extinction ratio which increases the shot noise.
Abstract: The effects of lasing time delay of injection laser diodes in digital fibre optic communication systems are considered. The solution of applying a constant dc bias is considered taking into account the resulting non-zero extinction ratio which increases the shot noise. An optimisation procedure is formulated for the bias of a laser diode and optimum bias values for different cases are calculated.
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Journal ArticleDOI
TL;DR: In this article, it is shown that a proper front-end design incorporates a high-impedance preamplifier which tends to integrate the detector output, and this must be followed by proper equalization in the later stages of the linear channel.
Abstract: This paper is concerned with a systematic approach to the design of the “linear channel” of a repeater for a digital fiber optic communication system. In particular, it is concerned with how one properly chooses the front-end preamplifier and biasing circuitry for the photodetector; and how the required power to achieve a desired error rate varies with the bit rate, the received optical pulse shape, and the desired baseband-equalized output pulse shape. It is shown that a proper front-end design incorporates a high-impedance preamplifier which tends to integrate the detector output. This must be followed by proper equalization in the later stages of the linear channel. The baseband signal-to-noise ratio is calculated as a function of the preamplifier parameters. Such a design provides significant reduction in the required optical power and/or required avalanche gain when compared to a design which does not integrate initially. It is shown that, when the received optical pulses overlap and when the optical channel is behaving linearly in power,1 baseband equalization can be used to separate the pulses with a practical but significant increase in required optical power. This required power penalty is calculated as a function of the input and equalized pulse shapes.

700 citations

Journal ArticleDOI
TL;DR: In this paper, the inter/cross modulation levels occurring in signals from stripe-geometry (GaAl) were investigated by computer simulation for the case of time-division multiplexed (TDM) pulse-analog modulation (PAM).
Abstract: Inter/cross modulation levels occurring in signals from stripe-geometry (GaAl)As double-heterostructure diode lasers are investigated by computer simulation for the case of time-division multiplexed (TDM) pulse-analog modulation (PAM). It is shown that pulse-position modulation (PPM) is the preferred modulation scheme for high pulse rates, and inter/cross modulation levels are evaluated for the format TDM-PPM. It is shown that the inter/cross modulation level is greatly improved when diode lasers are biased above threshold. Based on this evaluation, it is concluded that effectively inter/cross modulation-free optical transmission at a pulse rate up to 108 \times 10^{6} pulses per second by TDM-PPM is feasible. This limiting rate permits the transmission of 12 color TV channels or 10800 telephony channels.

5 citations

Journal ArticleDOI
TL;DR: In this article, the influence of the source-drive duty factor on the performance of a digital fiber-optic communication system was explored and it was shown that, for a fiber with known dispersion, an optimum duty factor exists which offers significant s.n.r.d. advantages over a system with impulsive excitation.
Abstract: The influence of the source-drive duty factor on the performance of a digital fibre-optic communication system is explored. The system considered utilises an l.e.d. source and either a p?i?n or avalanche photodetector. It is shown that, for a fibre with known dispersion, an optimum duty factor exists which offers significant s.n.r. advantages over a system with impulsive excitation.

1 citations