Loop topology based white light interferometric fiber optic sensor network for application of perimeter security

Abstract

A loop topology based white light interferometric sensor network for perimeter security has been designed and demonstrated. In the perimeter security sensing system, where fiber sensors are packaged in the suspended cable or buried cable, a bi-directional optical path interrogator is built by using Michelson or Mach-Zehnder interferometer. A practical implementation of this technique is presented by using an amplified spontaneous emission (ASE) light source and standard single mode fiber, which are common in communication industry. The sensor loop topology is completely passive and absolute length measurements can be obtained for each sensing fiber segment so that it can be used to measure quasi-distribution strain perturbation. For the long distance perimeter monitoring, this technique not only extends the multiplexing potential, but also provides a redundancy for the sensing system. One breakdown point is allowed in the sensor loop because the sensing system will still work even if the embedded sensor loop breaks somewhere.

Intelligent detection and identification in fiber-optical perimeter intrusion monitoring system based on the FBG sensor network

“…In particular, OFS does not need any power supply along the fiber link, and hence it is an ideal choice for long or medium long distance applications in harsh field environments. Typical OFS technologies in the security area include the phase-sensitive optical time domain reflectometry (Φ-OTDR) [5][6][7] and many other OTDR technologies [8], Sagnac, Michelson, Mach-Zehnder (M-Z) and their combination structures [9][10][11][12], white light interferometers [13], and quasi-distributed FBG sensor networks [14][15][16][17][18][19].…”

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.…”

Analog processing based vibration measurement technique using michelson interferometer

“…Many other parameters are also measured using the change in the pathlength of the interferometer, for example, strain/pressure, temperature etc. [14,15].…”