As a future plan, an advanced gravitational-wave detector will employ an optical configuration of resonant sideband extraction (RSE), achieved with an additional mirror at the signal-detection port of the power-recycled Fabry-Perot Michelson interferometer. To control the complex coupled cavity system, one of the most important design issues is how to extract the longitudinal control signals of the cavities. We developed a new signal-extraction scheme which provides an appropriate sensing matrix. The new method uses two sets of sidebands: one of the sideband components satisfies the critical coupling ondition for the RSE interferometer and reaches the signal-extraction port, and the other sideband is completely reflected by the Michelson interferometer. They provide a diagonalized sensing matrix and enable the RSE control to be robust.
@article{arxiv.0805.3960,
title = {Development of signal-extraction scheme for Resonant Sideband Extraction},
author = {K. Kokeyama and K. Somiya and F. Kawazoe and S. Sato and S. Kawamura and A. Sugamoto},
journal= {arXiv preprint arXiv:0805.3960},
year = {2008}
}