All-fiber Mach-Zehnder interferometers for sensing applications

Abstract

We propose and demonstrate a thinned fiber based Mach-Zehnder interferometer for multi-purpose sensing applications. The sensor head is formed by all-fiber in-line singlemode-multimode-thinned-singlemode (SMTS) fiber structure, only using the splicing method. The principle of operation relies on the effect that the thinned fiber cladding modes interference with the core mode by employing a multimode fiber as a mode coupler. Experimental results showed that the liquid refractive index information can be simultaneously provided from measuring the sensitivity of the liquid level. A 9.00 mm long thinned fiber sensor at a wavelength of 1538.7228 nm exhibits a water level sensitivity of -175.8 pm/mm, and refractive index sensitivity as high as -1868.42 (pm/mm)/RIU, respectively. The measuring method is novel, for the first time to our knowledge. In addition, it also demonstrates that by monitoring the wavelength shift, the sensor at a wavelength of 1566.4785 nm exhibits a refractive index sensitivity of -25.2935 nm/RIU, temperature sensitivity of 0.0615 nm/°C, and axial strain sensitivity of -2.99 pm/με, respectively. Moreover, the sensor fabrication process is very simple and cost effective.

Study of Interference Wavelength Characteristics of Fiber Bragg Grating Modulated All-Fiber Inline Mach–Zehnder Interferometer

“…The enveloping MZI transmission arrives from interference between core modes and several cladding modes, and is modulated by fluctuations in the core modes or cladding modes. (1)(2)(3) In our experiment, the lower order mode interference dip wavelengths were almost unchanged as the wavelength of the FBG shifted, and the higher order interference dip wavelength shifted with a FBG with a high modulation ratio (3.78). This kind of device could effectively improve the sensitivity of slight mode changes, which makes it attractive for many communication and sensing applications.…”

“…When these modes arrive at the FBG, they will be reflected by the FBG and the reflection wavelengths can be expressed as follows (2) …”

“…(1)(2)(3) Recently, an optical fiber Mach-Zehnder interferometer (MZI) cascaded or inscribed on an optical fiber Bragg grating (FBG) has attracted significant interest because of its special spectrum characteristics and refractive index sensing. New kinds of refractometers have been proposed based on a single modemultimode-single mode (SMS) fiber structure followed by a FBG or chirp FBG.…”

Applications of Mach-Zehnder Interferometry to Studies on Local Deformation of Polymers Under Photocuring

“…Compared to other interferometers like Michelson, the separation of the two arms of MZI can provide a wide application due to large and freely accessible working space though the optical alignment is relatively diicult. Taking advantage of this spacious working place, MZI has been utilized for various experiments: electron interferometer functioning in high magnetic ield [3], low visualization and low measurements [4], for sensing applications [5]. Furthermore, optoluidic Mach-Zehnder interferometer for sensitive, label-free measurements of refractive index of luids was also developed [6].…”

Dispersion effects of high-order-mode fiber on temperature and axial strain discrimination

“…In this paper, a HOMF-based fiber modal interferometer supporting three dominant modes is achieved with distinct chromatic dispersion of each guided mode and intermodal dispersion. Compared to conventional multimode interference structures (SMF-multimode-SMF structures, taper or lateral-offset in fiber Mach-Zehnder interferometers [23][24][25][26][27][28][29][30][31][32][33][34][35]) with a great amount of high-order optical modes, the proposed HOMF modal interferometer supports only a few steady core-guided modes which only need to be calibrated once for sensing response which is essential for practical applications. Thus the HOMF-based sensor here could be deployed for highly accurate discrimination based on the precise dispersion measurement and analysis on intermodal coupling with a novel phase demodulation scheme.…”