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Proceedings Paper

Optical waveform generation using a directly modulated laser
Author(s): John C. Cartledge; Abdullah S. Karar; Kim Roberts
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Paper Abstract

The capability of a directly modulated laser (DML) can be dramatically enhanced through precise control of the drive current waveform based on digital signal processing (DSP) and a digital-to-analog convertor (DAC). In this paper, a novel method to pre-compensate fiber dispersion for metro and regional networks is described for a bit rate of 10.709 Gb/s using a DML. A look-up table (LUT) for the drive current is optimized for dispersion mitigation. The entries of the LUT are determined based on the effects of the DML adiabatic and transient chirp on pulse propagation, the nonlinear mapping between the input current and the output optical power, and the bandwidth of the DML package. A DAC operating at 2 samples per bit (21.418 GSa/s with 6 bit resolution) converts the digital samples at the output of the LUT to an analog current waveform driving the DML. Experimental results for a bit rate of 10.709 Gb/s and on-off keying demonstrate a transmission reach of 252 km using a DML intended for 2.5 Gb/s operation and 608 km using a chirp managed laser intended for 10 Gb/s operation. Using this approach (DSP + DAC), the generation of 10.709 Gb/s differential phase shift keying (DPSK) and 56 Gb/s 16-ary quadrature amplitude modulation, sub-carrier multiplexed (QAM SCM) optical signals using the direct modulation of a passive feedback laser is also presented. 6-bit DACs operating at sampling rates of 21.418 GSa/s and 28 GSa/s, respectively, was used to generate the requisite analog current waveform.

Paper Details

Date Published: 11 October 2013
PDF: 15 pages
Proc. SPIE 8915, Photonics North 2013, 89150J (11 October 2013); doi: 10.1117/12.2037997
Show Author Affiliations
John C. Cartledge, Queen's Univ. (Canada)
Abdullah S. Karar, Queen's Univ. (Canada)
Kim Roberts, Ciena Corp. (Canada)

Published in SPIE Proceedings Vol. 8915:
Photonics North 2013
Pavel Cheben; Jens Schmid; Caroline Boudoux; Lawrence R. Chen; André Delâge; Siegfried Janz; Raman Kashyap; David J. Lockwood; Hans-Peter Loock; Zetian Mi, Editor(s)

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