Frequency dependence of slab coupled optical sensor sensitivity

Abstract

This paper presents the frequency-dependent sensitivity of slab-coupled optical fiber sensors (SCOSs). This dependence is caused by the frequency characteristics of the relative permittivity. We show experimentally the frequency dependence of SCOS sensitivity for frequencies in the range of 1 kHz to 1 MHz for SCOS fabricated with both potassium titanyl phosphate (KTP) and lithium niobate (LiNbO(3)). We conclude that x-cut KTP SCOSs are preferred for measuring fields above 300 kHz as they are 1.55× more sensitive than x-cut LiNbO(3) SCOSs to the higher frequency fields. However, since KTP SCOSs experience increasing permittivity for low frequencies, SCOSs made with LiNbO(3) may be used for low frequency sensing applications due to their flat sensitivity response. For a 10 kHz electric field, an x cut LiNbO(3) SCOS is approximately 3.43× more sensitive than an x-cut KTP SCOS.

Push–pull slab coupled optical sensor for measuring electric fields in a vibrational environment

“…The SCOS would also have to be fabricated to ensure sufficient resonant coupling between the crystal and fiber to yield sufficient sensitivity. Figure 4 shows that, by transmitting a laser through the SCOS with a wavelength that lies on a resonance edge, the electric field causes a change in the transmitted power [12].…”