An overview is given of the direct modulation performance of high-speed semiconductor lasers. The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.

High-speed modulation of semiconductor lasers

Chirp-induced dispersion penalties in high-bit-rate optical fiber transmission are assessed using numerical integration of laser rate equations and a Fourier transform fiber dispersion routine. The roles of the imposed modulation waveform and laser design parameters are evaluated from computer generated eye diagrams and simple analytical observations. Consistent with experiment, we find device dependent optimum laser extinction ratios. In addition, we address the delicate balance between nonlinear chirp-induced dispersion penalties and the speed limitations imposed by linear current filtering on both the laser transmitter and the receiver. These considerations become increasingly important at higher bit rates such as 8 Gbit/s.

Computer simulation of high-bit-rate optical fiber transmission using single-frequency lasers

This paper presents an introduction to the principles of lightwave system engineering. The treatment is historical rather than categorical-lightwave systems are described in terms of their evolution through four generations of technology, from a first generation operating at 0.85 μm wavelength over multimode fiber to a fourth generation employing coherent techniques at 1.55 μm. Basic engineering considerations such as fiber dispersion and receiver sensitivity are introduced early, then refined as the discussion progresses toward higher-performance, more sophisticated systems. The fundamental mechanisms that limit the performance of a given technology are quantified, and a figure of merit, the product of bit rate times maximum repeater spacing, is estimated. Values of this product range from about 2 Gbits/s . km for first-generation technology to roughly 900 Gbits/s . km for coherent systems.

http://ieeexplore.ieee.org/iel5/3/23078/01072601.pdf

Lightwave primer

The 25 years since the founding of the Journal of Lightwave Technology have seen more than three orders of magnitude increase in the capacity of optical transmission systems. This dramatic increase was brought about by the deployment of WDM and advances in high-speed transmission technologies.

High-Capacity Optical Transmission Systems

Techniques for the synthesis of an optical signal predistorted to compensate for fiber dispersion are discussed theoretically. A scheme for very high bit rate (>10 Gbit/s) time-division-multiplexed transmission is proposed which neither requires extremely short pulse sources nor suffers from their inherent dispersion limitations. The rudimentary aspects of the techniques have been verified experimentally by demonstrating both enhanced and degraded transmission of a 4-GHz modulated signal at 1.55 μm over 10-30 km of optical fiber.

Dispersion compensation by active predistorted signal synthesis

Using a multiplexer and demultiplexer built from discrete GaAs FET's, a directly modulated distributed feedback laser, and a low capacitance avalanche photodiode receiver, we have achieved transmission at 4 Gbit/s over 103 km of single-mode optical fiber at 1.54 μm.

R. Yen

Papers

4-Gbit/s transmission over 103 km of optical fiber using a novel electronic multiplexer/demultiplexer