Simultaneous measurement of strain and torsion based on a seven-core fiber Mach-Zehnder interferometer

A Mach-Zehnder interferometer based on seven-core fiber (SCF) and muti-mode fiber (MMF) is proposed and experimentally demonstrated. The interferometer is fabricated by splicing a segment of SCF spliced with two MMFs. The SCF length and MMF length are 5cm and 1cm, respectively. When the broadband light is injected into the interferometer through a lead-in single mode fiber, a pronounced interference pattern appears in the transmission spectrum. By monitoring the wavelength and power shifts of interference dips, simultaneous measurement of strain and torsion can be achieved. The experimental results show that the wavelengths at interference dip have a blue shift with the increases of strain, but the wavelength does not respond to the torsion. The power sensitivities of the interference dip to the strain and torsion are sensitivities are 0.001dB /° and 0.16dB/°, respectively. The simultaneous measurement of strain and torsion is demonstrated based on the sensitive matrix. The proposed MZI exhibits the advantages of easy fabrication, low cost, and simultaneous measurement of strain and torsion, which will make a significant contribution to torsion measurement.