LIGO (source code)
= LIGO
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<LIGO> measures <gravitational wave>-induced changes in the relative lengths of widely separated <interferometer> arms. <Laser> light travels along perpendicular arms, reflects from suspended <mirrors> and recombines; a change in relative optical <phase> alters the detected signal. Arm <optical cavities> increase the interaction time, while vibration isolation and mirror suspension reduce unwanted motion.<Advanced LIGO by J. Aasi and others>[Abstract and detector configuration: Michelson geometry, arm cavities and noise-control systems]{ref}
The <strain> scale is roughly the differential length change divided by arm length. Calibration converts the optical readout into <strain>, and agreement between separated observatories helps distinguish an astrophysical signal from a local disturbance.
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