Journal article

Enabling Complex Modulation of Directly Modulated Signals Using Laser Frequency Chirp

Di Che, Qian Hu, Feng Yuan, Qi Yang, William Shieh

IEEE Photonics Technology Letters | IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC | Published : 2015

Abstract

Directly modulated laser (DML) with direct detection (DD) dominates the commercial optical short reach applications. When upgrading the DML-DD to higher data rate, the frequency chirp is commonly regarded as a performance barrier. On the contrary, in this letter, we take advantage of the chirp to generate phase modulation along with the intensity, namely, realize complex modulation at transmitter using a single DML. Coherent detection (CD) is applied to recover this 2 dimensional (2-D) signal. A modified Viterbi algorithm (VA) conducts maximum likelihood decoding utilizing the signal intensity and differential phase in receiver digital signal processing (DSP). By making decision using 2-D in..

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