Solid-core photonic crystal fiber (PCF) with a permanent helical twist exhibits dips in its transmission spectrum at certain wavelengths. These are associated with the formation of orbital angular momentum states in the cladding. Here we investigate the tuning of these states with mechanical torque and axial tension. The dip wavelengths are found to scale linearly with both axial strain and mechanical twist rate. Analysis shows that the tension-induced shift in resonance wavelength is determined both by the photoelastic effect and by the change in twist rate, while the torsion-induced wavelength shift depends only on the change in twist rate. Twisted PCF can act as an effective optically monitored torque-tension transducer, twist sensor, or strain gauge.
© 2013 Optical Society of America
Fiber Optics and Optical Communications
Original Manuscript: October 3, 2013
Revised Manuscript: November 7, 2013
Manuscript Accepted: November 12, 2013
Published: December 10, 2013
Xiaoming Xi, Gordon K. L. Wong, Thomas Weiss, and Philip St.J. Russell, "Measuring mechanical strain and twist using helical photonic crystal fiber," Opt. Lett. 38, 5401-5404 (2013)