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Department of Engineering, ICT and Technologies for Energy and Transport Patent Title 10.88 BOFDA Optical demodulation based technique Method for measuring the Brillouin 10.86 distri on along an cal Įber based on the 10.84 cal demodul of the signals, and related 10.82 apparatus. Brillouin frequency shift [GHz] 10.80 10.78 Ref. CNR 1745 10.76 Assignee(s): CNR 10.74 10.72 CNR In ute: IREA 0 50 Position along the fiber [m] 200 250 100 150 Main Inventor: Romeo Bernini Countries: US Priority date: 09/06/2006 Abstract The patent refers to a system and a method for measurement of the Brillouin frequency shi ƉƌŽĮůe along an l Įber. The proposed approach is based on the s ed Brillouin shi s ering - available also in standard telecomm n ĮďĞƌƐ – and permits to performs distributed strain/temperature measurements. The proposed approach performs frequency domain measurements, avoiding the need to detect fast signal as usually happen in me domain approaches. In par cular, the system is based on an al n of the signals that permits to measure the Brillouin prŽĮůe with high res n and accuracy. Background Nowadays, distributed Įďer sensors based on s mulated Brillouin s ering are widely used for distributed strain monitoring. However, the sensors developed at the state of the art require measurement system working in me domain that requires the use of high frequency electronics. Technology The method can be implemented using two approaches. In the Įƌst one, a pump signal with sinusoidal modul on at frequency f1 and an op cal probe signal with sinusoidal modul on at frequency f2 are launched into the Įber. In the second one, a con nuous pump signal and an op cal probe signal with sinusoidal mo on at frequency f2 are used. The probe signal at the exit of the measurement Įber is y demodulated at a frequency f1. Advantages and Applica ons The patent refers to a system and a method for measurement of the Brillouin frequency shi proĮle along an ŽƉƟĐĂů ĮďĞƌ͘ /Ŷ ƉĂƌƟĐƵůĂƌ͕ ŽƉƟĐĂů ĚĞŵŽĚƵůĂƟŽŶ ƚĞĐŚŶŝƋƵĞƐ ĂƌĞ ƵƐĞĚ͕ ŝŶ ŽƌĚĞƌ ƚŽ ŝŶĐƌĞĂƐĞ ƚŚĞ ƌĞƐŽůƵƟŽŶ ĂŶĚ ƚŚĞ ĂĐĐƵƌĂĐLJ ĂŶĚ͕ ĨƵƌƚŚĞƌŵŽƌĞ͕ ƚŽ ƉĞƌŵŝƚ Ă ƐŝŵƉůŝĮĐĂƟŽŶ ŽĨ ƚŚĞ ŵĞĂƐƵƌŝŶŐ ƐLJƐƚĞŵƐ ĂǀŽŝĚŝŶŐ ƚŚĞ ƵƐĞ ŽĨ ŚŝŐŚ ĨƌĞƋƵĞŶĐLJ ĞůĞĐƚƌŽŶŝĐƐ͘ /Ŷ ĨĂĐƚ͕ ƚŚĞ ƐŝŐŶĂů ƚŽ ďĞ ŵĞĂƐƵƌĞĚ ŝƐ Ă ůŽǁ ĨƌĞƋƵĞŶĐLJ ƐŝŐŶĂů Ăƚ Ă ĮdžĞĚ ĨƌĞƋƵĞŶĐLJ Ĩŵ͘ Development stage The proposed approach has been validated by some experimental laboratory tests with a sp al re of 3m along a 230m long Įber. 43