Use of a fiber-optic Mach-Zehnder interferometer for creating a deformometer with extended gage length

Use of 3×3 Coupler in the Fiber Optic Strainmeter Based on Mach-Zehnder Interferometer

“…Sensing optical fiber wound between mobile (4) and fixed (6) half of the cylinder. A mobile half of the cylinder fastens by the end of an extensive rope (2) which second end is fixed on a column (1). Afterword the signal and reference waves are combined at the 3×3 coupler (9).…”

“…In fiber optic strainmeter the optical scheme of the Mach-Zehnder interferometer [1] providing a possibility of registration of deformations to 10 −12 m is convenient for application. However, the high sensitivity of the interferometer leads to the drift of working point caused by changes of conditions of the environment, for example, of temperature and pressure.…”

Fiber Optic Long Baseline Deformometer for Pit Wall Rock Monitoring System

“…For FOS based on the Mach−Zehnder interferometer there is a problem of the output signal fading of the strainmeter when the external temperature changes, and false signals about the rocks displacement appear. Also note the rather complex design of FOS [5]. Taking into account the above and the world experience in the FOS design to monitor the rocks deformation, it was decided to create a fundamentally new simplified design of long-base strainmeters operating on a completely different principle, with their subsequent use for monitoring systems to prevent the collapse of quarry walls.…”

“…1 shows the measuring circuit of the FOS, which was used in the experiment. The proposed FOS design is similar to the FOS design described in [5], but differs from it in the principle of operation of the measuring part. Its basis is a single-mode optical fiber type G 652 (9/125 µm), which effectively operates in the light wavelength range from 1310 to 1625 nm with rather low losses (up to 0.2 dB /km).…”

“…The advantages of FOSs use (their ability to work in explosive environments and low power consumption) are described in [1][2][3]5]. Instruments used in the experiment: optical radiation source SmartPocket OLS-34/35/36 (USA); optical power meter SmartPocket OLP-38 (USA) with measurement error ±3% and dynamic measurement range from −50 to +26 dB; measuring scale with division value 1 mm and measurement error 0.5 mm.…”