Modified sagnac/mach-zehnder interferometer for distributed disturbance sensing

A distributed fiber vibration sensor utilizing dispersion induced walk-off effect in a unidirectional Mach-Zehnder interferometer

“…For distributed optical fiber sensing systems demonstrated so far, a large number of signals are acquired and processed in order to obtain a reasonable signal to noise ratio (SNR), so the acquisition time is typically on the order of few minutes. They fall into two categories, one is based on optical fiber interferometers [1][2][3][4][5][6][7][8][9][10] and the other is based on optical backscattering [11][12][13][14][15].…”

“…In order to obtain the vibration location of distributed optical fiber sensor system, either modified optical interferometer structures are adopted or two kinds of optical interferometer structures are merged together, such as incorporating an MZI with a Sagnac loop [3], modified Sagnac/MZI [4], twin Sagnac interferometers [5,6], merged Sagnac-Michelson interferometers [7], dual Michelson interferometers [8], dual MZIs [9] and scanning MZI [10]. Due to the differences between correlated signals in separate interferometers caused by noises or changes of polarization states, both the spatial resolution and measurement range for twin optical interferometer structures are limited.…”

Interferometric distributed sensing system with phase optical time-domain reflectometry

“…Up to now, the distributed optical fiber measurements mainly include optical fiber interferometer sensors and optical backscattering based sensors. Interferometer sensors acquire distributed information by integration of the phase modulation signals, and usually two interferometers are used to determine the position, including combining the Sagnac to a Michelson interferometer [1], modified Sagnac/Mach-Zehnder interferometer [2], twin Sagnac [3]/Michelson [4]/Mach-Zehnder [5] interferometers, and adopting a variable loop Sagnac [6]. Another distinguished technique is the use of optical backscattering based sensors.…”

Modified Sagnac interferometer for distributed disturbance detection

“…For many years, fiber optic distributed sensor based on Sagnac interferometer [1][2][3][4][5][6][7][8][9][10] has been used to locate a disturbance applied to its sensing fiber, because of its inherent balance and high sensitivity. It includes Sagnac and Mach-Zehnder [1,8], Sagnac and Michelson [2,7], Sagnac and Sagnac [2,5,6], Sagnac [3,10], and differentiating ring [4,9].…”

“…It includes Sagnac and Mach-Zehnder [1,8], Sagnac and Michelson [2,7], Sagnac and Sagnac [2,5,6], Sagnac [3,10], and differentiating ring [4,9]. However, the sensing loop structure of the Sagnac interferometer brings some troubles, which prevent its further application especially in the field of monitoring longdistance pipeline.…”