The Laser Interferometer Gravitational Wave Observatory ( LIGO ) consists of two widely separated 4 km laser interferometers designed to detect gravitational waves from distant astrophysical sources in the frequency range from 10 Hz to 10 kHz .
The first observation run of the Advanced LIGO detectors started in September 2015 and ended in January 2016 .
A strain sensitivity of better than 10 ^ { -23 } / \sqrt { \text { Hz } } was achieved around 100 Hz .
Understanding both the fundamental and the technical noise sources was critical for increasing the astrophsyical strain sensitivity .
The average distance at which coalescing binary black hole systems with individual masses of 30 M _ { \odot } could be detected above a signal-to-noise ratio ( SNR ) of 8 was 1.3 Gpc , and the range for binary neutron star inspirals was about 75 Mpc .
With respect to the initial detectors , the observable volume of the Universe increased by a factor 69 and 43 , respectively .
These improvements helped Advanced LIGO to detect the gravitational wave signal from the binary black hole coalescence , known as GW150914 .