Optical Vernier Effect: Recent Advances and Developments

Abstract

The optical analog of the Vernier effect applied to fiber interferometers is a recent tool to enhance the sensitivity and resolution of optical fiber sensors. This effect relies on the overlap between the signals of two interferometers with slightly detuned interference frequencies. The Vernier envelope modulation generated at the output spectrum presents magnified sensing capabilities (i.e., magnified wavelength shift) compared to that of the individual sensing interferometers that constitute the system, leading to a new generation of highly sensitive fiber sensing devices. This review analyses the recent advances and developments of the optical Vernier effect from a fiber sensing point-of-view. Initially, the fundamentals of the effect are introduced, followed by an extensive review on the state-of-the-art, presenting all the different configurations and types of fiber sensing interferometers used to introduce the optical Vernier effect. This paper also includes an overview of the complex case of enhanced Vernier effect and the introduction of harmonics to the effect.

Study of the Vernier Effect Based on the Fabry–Perot Interferometer: Methodology and Application

“…In this work, we studied the conditions for generating the Vernier effect and its applications in practice. Consistent with previous studies of Vernier effect [28,37], the envelope of the Vernier effect is regenerated when the OPL of the interferometer changes proportionally. However, we found that there is a regular expansion and contraction of the The temperature characteristics of the combination of the reference and the sensing FPI are tested by placing the sensors on a heating table with a temperature range from 41 • C to 45 • C. To clearly compare the interference spectra under different temperature, Figure 13c,d shows the total reflectance spectra based on Vernier effect when the temperature rises and drops.…”

“…In this work, we studied the conditions for generating the Vernier effect and its applications in practice. Consistent with previous studies of Vernier effect [28,37], the envelope of the Vernier effect is regenerated when the OPL of the interferometer changes proportionally. However, we found that there is a regular expansion and contraction of the envelope during the regeneration process, which means that there is a turning point in the trend of change.…”

“…Optical fiber sensors based on the Vernier effect can be categorized into two approaches: (i) Compact structures, which consists of two interferometers connected in series that interact with each other; however, the structure is relatively compact, such as that of cascaded FPIs [15][16][17][18][19], Mach-Zehnder interferometers (MZI) [20], Sagnac loops [21], and hybrid cascaded configurations [22]; and (ii) separated structures, which consists of two independent interferometers that are physically separated and do not interfere with each other, for example, the parallel combination of two interferometers of the same type [23][24][25] or a mixed configuration of different types of interferometers [26,27]. The introduction of the optical Vernier effect using FPIs is quite popular, corresponding to almost half of the publications on this topic [28].…”

Dual-wavelength switchable single-mode lasing from a lanthanide-doped resonator

“…The observed mode-selection phenomenon can be understood with the Vernier effect, which is caused by the detuning (Δ)-dependent destructive interference 4 , 5 , 12 , 14 , 44 , 45 . In principle, the magnified free spectral range ( FSR enlarged ) of the Vernier envelope 46 , 47 can be expressed as a function of the FSRs of the two coupled microdisks where FSR right and FSR left are the FSRs of the two tangent microdisks. For the case of d left = 100 μm, the diameter difference between two microdisks (Δd) is as small as 80 nm to realize the designed spectral range (300 nm).…”

Advanced Fiber Sensors Based on the Vernier Effect

“…Leveraging on the slight scale difference between the Vernier and the main ruler, the Vernier effect was initially employed in the Vernier caliper to improve the length measurement accuracy. Recently, the Vernier effect has been revealed to be a useful technique to enhance the sensing performance of optical fiber sensors, which can greatly improve the detection resolution of fiber sensors [ 6 , 7 ]. In fact, the Vernier-effect-based optical fiber sensors have demonstrated a huge potential to achieve high sensitivity and resolution, and research on optical fiber sensors based on the Vernier effect rapidly became a popular topic among researchers during the last five years.…”