Sleep centre (sleep laboratory)
A unit where sleep tests are done, where you stay overnight, and that works with sleep physicians and technologists.
A little more detail
A unit with sleep medicine physicians and technologists where tests such as attended polysomnography, titration studies and the MSLT are done. It is where the diagnosis is made when a home test is not suitable or is inconclusive.
Source: Kapur VK, Auckley DH, Chowdhuri S et al. Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2017;13(3):479-504. doi:10.5664/jcsm.6506