Patent ID: 8891071

Claim:
An apparatus comprising: an optical fiber measurement element disposed around at least a portion of a conduit; a reflector coupled to one end of the optical fiber measurement element; a narrowband light source to inject a first optical signal into a first beam splitter/coupler to split the first optical signal into a second optical signal propagating in a first optical fiber and a third optical signal propagating in a second optical fiber; a delay section disposed in the second optical fiber; a second beam splitter/coupler to combine and direct the second optical signal and the third optical signal into the optical fiber measurement element to the reflector, the reflector reflecting the second optical signal and the third optical signal back through the second beam splitter/coupler such that at least a portion of the reflected second optical signal propagates through the second optical fiber and at least a portion of the third optical signals propagates through the first optical fiber; and an optical detector to sense an interference between the reflected second optical signal and the reflected third optical signal caused by an encoded pressure signal propagating in a fluid flowing in the conduit and to output a first signal related thereto.