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N. Albakay, A. Alotham, I. Barshushi“Bit Error Rate Monitoring for Automatic Bias Control of Quadrature Amplitude Modulators" 2021 World Academy of Science, Engineering and Technology International Journal of Information and Communication Engineering, June 2021.

The paper titled "Bit Error Rate Monitoring for Automatic Bias Control of Quadrature Amplitude Modulators," authored by Naji Ali Albakay, Abdulrahman Alothaim, and Isa Barshushi, was published in the World Academy of Science, Engineering and Technology International Journal of Information and Communication Engineering in June 2021.

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This research addresses the issue of bias drift in Mach-Zehnder Modulators (MZMs) used in quadrature amplitude modulation (QAM) transmitters. Bias drift, caused by factors such as temperature changes, vibration, and aging, can distort the QAM signal and degrade bit error rate (BER) performance. To combat this, the authors propose an automatic bias control (ABC) technique that utilizes BER measurements in conjunction with a gradient descent optimization algorithm. This method aims to lock the MZM's operating point, or Q point, to its optimal position, thereby enhancing signal integrity. 

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The proposed ABC technique is particularly advantageous because it focuses directly on BER, a critical performance metric, and compensates for bias drifting independently of other system variations, such as fluctuations in laser source output power. The authors validated their approach through simulations using OptiSystem software, demonstrating its effectiveness for both 4-QAM and 16-QAM transmitters.