  We present a review of modern optical techniques being used and developed for
the field of gravitational wave detection. We describe the current
state-of-the-art of gravitational waves detector technologies with regard to
optical layouts, suspensions and test masses. We discuss the dominant sources
and noise in each of these subsystems and the developments that will help
mitigate them for future generations of detectors. We very briefly summarise
some of the novel astrophysics that will be possible with these upgraded
detectors.
