This article explores two types of feedback used to control optical traps: position feedback, which was shown to be equivalent to force feedback, and integral feedback. The ability of each of these types of feedback to lower the measurement SNR in single molecule experiments is evaluated and compared to the open-loop case. While position feedback did not result in any improvement in the SNR, the case of integral feedback results in an improvement. Integral feedback is shown to improve the SNR of the measured signal of interest, and is relatively robust and easy to implement. It is also shown that integral feedback acts as an exogenous force estimator.

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