Ultrahigh-sensitivity temperature fiber sensor based on multimode interference

Abstract

The proposed sensing device relies on the self-imaging effect that occurs in a pure silica multimode fiber (coreless MMF) section of a single-mode-multimode-single-mode (SMS)-based fiber structure. The influence of the coreless-MMF diameter on the external refractive index (RI) variation permitted the sensing head with the lowest MMF diameter (i.e., 55 μm) to exhibit the maximum sensitivity (2800 nm∕RIU). This approach also implied an ultrahigh sensitivity of this fiber device to temperature variations in the liquid RI of 1.43: a maximum sensitivity of −1880 pm∕°C was indeed attained. Therefore, the results produced were over 100-fold those of the typical value of approximately 13 pm∕°C achieved in air using a similar device. Numerical analysis of an evanescent wave absorption sensor was performed, in order to extend the range of liquids with a detectable RI to above 1.43. The suggested model is an SMS fiber device where a polymer coating, with an RI as low as 1.3, is deposited over the coreless MMF; numerical results are presented pertaining to several polymer thicknesses in terms of external RI variation.

High sensitivity temperature sensor based on a polymer filled hollow core optical fibre interferometer

“…However, the temperature sensitivity remains as low as -70 pm/ o C for a graded index MMF sensor and 18pm/ o C for a step index MMF sensor [13]. Apart from the conventional SMS, a singlemode-coreless-singlemode (SCS) fibre sensor was also reported with a higher temperature sensitivity of 1880 pm∕°C [14]. This sensor was based on surrounding a short section of coreless fibre with a liquid with refractive index of 1.43, but this structure and sensor suffers from the significant disadvantages of lower stability and difficulty in packaging for real applications.…”

Single-mode—multimode—single-mode and lossy mode resonance-based devices: a comparative study for sensing applications

“…Particularly, the transmission bands obtained by the selfimage effect exhibit minimum losses (Soldano and Pennings 1995), and its central wavelength can be controlled as a function of the MMF segment dimensions, mainly the MMF segment length and diameter (Silva et al 2012). The MMF segment diameter is also responsible for the sensitivity of the device.…”

“…The first one is the single-mode-multimode-singlemode (SMS) structure, which is used in important fields such as sensing and optical communications (Ruiz-Pérez et al 2011;Silva et al 2012;Mohammed et al 2006). The basic physical principle of the SMS device is that light transmitted through the fundamental mode of the singlemode (SMF) segment is coupled to several modes into a multimode (MMF) segment and recoupled to the fundamental mode of another SMF spliced at the other side of the MMF (Silva et al 2012). Due to the phenomenon of…”

SMS fiber structure for temperature measurement using an OTDR

“…This temperature dependence can also be exploited to develop a temperature sensor. Some techniques can be utilized to extract the temperature information from the SMS fiber structure sensor, for example by measuring the temperature-induced shift in the peak wavelength of its spectrum [12], an intensity-based interrogation system [13], or a ratiometric power interrogation system [14].…”

“…Techniques in [12][13][14] could only be used for single-point measurement. In some industrial processes or a structural health monitoring system, a multi-point or quasi-distributed temperature measurement system is needed [15,16].…”