Abstract: Methods, structures, devices and systems are disclosed for implementing optical seismometers that detect seismic information based on optical interferometry. In one aspect, a device includes a first retroreflector attached to a mass of a seismometer, a second retroreflector attached to a member of a frame of the seismometer, the frame structured to suspend the mass, and optical components attached to the member of the frame and configured with the first and second retroreflectors to form an interferometer, in which a change in position of the mass is identified by detecting by a change in an optical path of a light beam generated by a light energy source transmitted to the interferometer.

Abstract: Methods, structures, devices and systems are disclosed for implementing optical seismometers that detect seismic information based on optical interferometry. In one aspect, a device includes a first retroreflector attached to a mass of a seismometer, a second retroreflector attached to a member of a frame of the seismometer, the frame structured to suspend the mass, and optical components attached to the member of the frame and configured with the first and second retroreflectors to form an interferometer, in which a change in position of the mass is identified by detecting by a change in an optical path of a light beam generated by a light energy source transmitted to the interferometer.

Abstract: Analog-to-digital conversion apparatus provides high-resolution conversion of input signals. Summing elements combine an analog input signal and an analog offset signal to generate a residual signal. A first integrator element integrates the residual signal, and a second integrator processes the first integrator output signal to produce a second integrator output signal. A comparator processes the first and second integrator output signals to produce a digital offset signal, the second integrator output signal is converted into a digital representation, and output elements process the digital offset signal and second integrator output signal to produce a digital representation of the analog input signal.