A signal acquisition and distance variation measurement system for laser ranging interferometers having a signal acquisition unit, comprising: - a frequency detection subsystem for detecting the frequency of a measurement signal of a received laser beam which is buried in noise wherein the frequency detection subsystem comprises an acquisition subsystem and a phase/frequency detector PLL, the frequency detection subsystem comprising a wavelet decomposition unit, a signal power estimation unit and an upsampling unit, wherein the wavelet packet decomposition unit is adapted to cut the electronics frequency range into several sub-bands, wherein the signal power estimation unit is adapted to detect the presence of a measurement signal in any of the frequency sub-bands, wherein the upsampling unit is adapted to process only the sub-band with the highest output power, and wherein the upsampling unit and all the units after it are not triggered by the wavelet packet decomposition unit and the signal power estimation unit in case no measurement signal is received; - a main PLL unit being coupled to the frequency detection subsystem for receiving the detected frequency of the measurement signal for phase estimation of the measurement signal; - a phasemeter band detection subsystem for detecting whether the frequency of the measurement signal is higher or lower than the frequency of a reference signal of a reference laser beam by operating a known change to the frequency of the reference signal and measuring the consequent change in the frequency of an interference signal for having the phase of the reference signal locked to the phase of the measurement signal. - a frequency detection subsystem for detecting the frequency of a measurement signal of a received laser beam which is buried in noise wherein the frequency detection subsystem comprises an acquisition subsystem and a phase/frequency detector PLL, the frequency detection subsystem comprising a wavelet decomposition unit, a signal power estimation unit and an upsampling unit, wherein the wavelet packet decomposition unit is adapted to cut the electronics frequency range into several sub-bands, wherein the signal power estimation unit is adapted to detect the presence of a measurement signal in any of the frequency sub-bands, wherein the upsampling unit is adapted to process only the sub-band with the highest output power, and wherein the upsampling unit and all the units after it are not triggered by the wavelet packet decomposition unit and the signal power estimation unit in case no measurement signal is received; - a main PLL unit being coupled to the frequency detection subsystem for receiving the detected frequency of the measurement signal for phase estimation of the measurement signal; - a phasemeter band detection subsystem for detecting whether the frequency of the measurement signal is higher or lower than the frequency of a reference signal of a reference laser beam by operating a known change to the frequency of the reference signal and measuring the consequent change in the frequency of an interference signal for having the phase of the reference signal locked to the phase of the measurement signal.