Simultaneous measurement of refractive index and temperature based on SPR in D-shaped MOF.

A surface plasmon resonance (SPR) sensor based on D-shaped microstructured optical fiber (MOF) is proposed to realize the simultaneous measurement of refractive index (RI) and temperature. The D-shaped flat surface coated with a gold layer is in direct contact with analyte as a sensing channel of RI, and one of the air holes near the fiber core is filled with chloroform to detect temperature. Two separate channels and birefringence caused by the asymmetric structure can distinguish the variations of RI and temperature independently, thus completely solving the cross-sensitivity problem. This is the first time to realize the simultaneous measurement of multiple parameters without matrix equations, to the best of our knowledge. Results show that the y-polarized peak supported by channel I only shifts with RI variation and is unaffected by the temperature floating. Similarly, the x-polarized peak supported by channel II is only influenced by the change of temperature in the external environment. The effect of gold layer thickness is investigated numerically, and the sensor sensitivity is identified both in wavelength and amplitude interrogations. This work is very helpful for the design and implementation of a highly sensitive, real-time, and distributed SPR sensor for multi-parameter measurement applications.