Abstract: Closed-form solutions are presented for frequency mismatch estimation in burst-mode coherent receivers. The expressions also apply to periodic pilot-signal bursts inserted into a continuous bit stream. The solutions are optimal in the mean-square-error sense for coherent optical receivers subject to random-walk phase fluctuations and high short-term laser-frequency stability. Low computational time-complexity of only O(n) and space-complexity as low as O(log(n)) are obtained, where n is the size of the estimation block. Better yet, when the pilot-signal is a Continuous Wave tone, the estimator is able to extend its performance up to the maximum correctable frequency-mismatch, which is one-half of the baud rate. We believe that these results contribute to fostering low-power transceiver technology for green communication networks Ver menos