This work presents a novel fiber optic Mach-Zehnder interferometer (MZI) sensor that can measure curvature due to its structure. This structure employs a 2-section MZI filter constructed from SMF-28 fiber using the core offset technique. The source in the 1480-1600 nm range shows intermodal energy interference between the core and the cladding and exhibits six spacing notches for sensing applications. The sensibility obtained was of 0.00018 nm/uW when curvature is applied. However, by including a thin film based on Zinc Oxide (ZnO) and another with Aluminum-doped zinc oxide (AZO) in the sensing arrangement, an increase in the sensitivity was detected with a value of 0.00015 nm/uW and 0.00016 nm/uW, respectively. This sensor can be used for applications in various fields, such as environmental monitoring, engineering, and process control.
In-line fiber Mach-Zehnder interferometers have become more popular than traditional electric sensors because of their small size, low cost, easy fabrication, resistance to electromagnetic interference, durability against extreme environments, and ease of use. This paper discusses the development, characteristics, and properties of a curvature-based Mach-Zehnder interferometer (MZI). The MZI comprises a filter made by splicing core-offset sections of a special mode fiber (SSMF) with a cladding diameter of 70 μm in an SMF-SSMF-SMF-SSMF-SMF (1m/25mm/30mm/25mm/1m) configuration. The SSMF splices act as the arms of the MZI, while the mismatch diameter sections serve as optical fiber couplers. The MZI was characterized by measuring the optical spectrum response when a broadband source of 1537.5 to 1600 nm was launched with a power of 10 dBm to transmit light through the arrangement. The optical spectrum analyzer (OSA) detects the transmitted light and analyzes its optical transmission characteristics, showing 5 notches of modal interferences into the longitude region. As a result of the experimental arrangement, the displacement and curvature sensitivities are 0.003 nm/μm and 0.509 nm/μm-1, respectively. The proposed sensor has potential advantages for measuring refractive index, pH, torsion, curvature, and temperature.
The Mach-Zehnder interferometer (MZI produces light interference due to the phase differences between the two paths. In this experiment, a 3-section MZI filter made of SMF-28 fiber with core-offset technique, which manually displaces the centers of the fiber core by 30 m was used with a 10dBm light source emitting in the 1480-1600 nm range. The results revealed intermodal energy interference between the core and the cladding and six spacing notches for sensing purposes.
In this work a design and analysis of a Fabry-Perot interferometer (FPI) based on a silicon wafer for possible application in a SF6 gas sensor used in electric power systems is presented. The sensor design is based on cross correlation spectroscopy principle with an FPI, which acts an optical modulator. Hence, due to characteristics of the FPI transmission spectrum, it can be used detect molecules with very well defined ro-vibrational lines such as those produced by diatomic and linear molecules. The design of the FPI depends mainly of the SF6 absorption wavelength peaks and of the optimum thickness of the silicon wafer. For this reason, in order to measure this absorption peaks a HITRAN database was used. The optimum thickness of the silicon wafer was calculated and simulated transmission spectrum. Finally, we demonstrated by using analytical simulations that a silicon wafer can be implemented as a FPI and used in a SF6 gas sensor.
In this paper a temperature sensing setup based on a Photonic Crystal Fiber (PCF) Mach-Zehnder Interferometer (MZI), coated with aluminum is proposed. Here, this interferometer is fabricated through the concatenation of two sections of Single Mode Fiber (SMF) with a segment of PCF between them. The SMF-PCF joint acts as beam splitter causing the excitement of PCF’s, both cladding and fundamental core modes. In the PCF-SMF union, the cladding modes couple again to the core of the SMF, and interfere with the fundamental core mode, this interaction results in an interference pattern spectrum. Moreover, the MZI was coated with aluminum, using the evaporation technique. By adding a thin metal layer to the PCF section, the general thermal coefficient of the structure changes, enhancing the sensitivity of the device. Experimental results show that a visibility of 13 dBm can be obtained and a sensitivity of 250 pm/°C. Finally, the proposed structure is simple, cost effective and easy to fabricate.
A torsion experimental sensing setup based on a Mach-Zehnder interferometer (MZI) with photonics crystal fiber is presented. The MZI was fabricated by fusion splicing a piece of photonic crystal fiber (PCF) between two segments of a single-mode fiber (SMF). Here, a spectral MZI fringe shifting is induced by applying torsion over the SMF-PCF-SMF. As a result a torsion sensitivity of 35.79 pm/ and a high visibility of 10 dB were achieved. Finally, it is shown that the sensing arrangement is compact and robust.
We present the fabrication and characterization of a mechanically induced long period grating (MLPG) using a grating period of 400 μm and 1m of NZ-DSF. Pressure is gradually applied up to 120 Lb at different angles like 0, 30, 45 and 60 degrees. An attenuation band is observed centered at a wavelength around 1064nm using a fiber position of 30 degrees with respect to the grating´s metal plate and a maximum pressure of 145 Lb. The loss band presents a maximum depth of 22dB and a bandwidth of approximately 10nm. Torsion and curvature characterizations did not change the output spectrum of the optical grating. However, temperature characterization depicted a small shifting which could be insignificant for some applications. Still, there is 16dB attenuation as temperature increases in a range from room temperature up to 450°C. These preliminary studies show that this 1064 nm centered wavelength MILPG might be used in a low linear dynamic range with temperature (75-300)°C as a temperature sensor.
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