Patent ID: 11959799
Assignee: ASELSAN ELEKTRONIK SANAYI VE TICARET ANONIM SIRKETI
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 15:
16. A phase sensitive optical time domain reflectometry based distributed acoustic sensing method eliminating a degradation in a sensing performance encountered due to a finite extinction ratio of optical elements, comprising the steps of;
generating a coherent Continuous Wave (CW) laser beam with a first linewidth for detecting vibration sources near a fiber optical cable,
adjusting a power of the coherent CW laser beam and filtering to eliminate at least some frequency components that are introducible during a power adjustment,
shaping the coherent CW laser beam into optical pulses by an optical pulse generator with a pulse shape,
generating an incoherent CW laser beam with a second linewidth, which is larger than the first linewidth, for degrading a coherence interference effect or a coherence length for a light injected into the fiber optical cable when the optical pulse generator is in an OFF state,
adjusting a power of an incoherent light and filtering the incoherent light, wherein a resulting incoherent light has a linewidth with a power of the resulting incoherent light that mimics a power of a coherent leakage light injected when the optical pulse generator is in the OFF state,
combining optical signals coming from optical paths with a combiner and forwarding the optical signals to a circulator,
injecting the optical signals to the fiber optic cable and forwarding back reflected Rayleigh scattering signals coming from the fiber optic cable to a gain and filter block,
adjusting a power level of the optical signals and filtering out the at least some frequency components on a returned Rayleigh backscattered signal,
measuring an optical power of the returned Rayleigh backscattered signal,
digitizing a measured analog optical power and processing a digitized optical signal power.