Liquid level and temperature sensing by using dual-wavelength fiber laser based on multimode interferometer and FBG in parallel

Discrete liquid level fiber sensor

“…Eventually the lowest power for each of the splitter become decreased too with reference to the highest power reading. Common problem with a liquid level sensor using other fiber based scheme such as the FBG and interferometer [2,5] is that the range of the liquid level is very limited to short range of a few centimeters. In contrast, the proposed sensor scheme can support greater range from short to very long up to a few meters.…”

“…The low insertion loss contributes to low overall loss for the total reflected power and hence maximizes the dynamic range of the sensor. The main advantage of this sensor scheme is that it could provide customization of liquid level measurement range up to hundred meters with simple configuration instead of the complicated point measurement scheme employed by MMI [9,[16][17][18], U-shaped [16,19,20,21] and POF [17,22,23,24] based sensors. Since our sensor is based on intensity measurement, it is suggested to have one of the multiple outputs acting as the reference signal using the ratio metric scheme.…”

“…Optical fiber sensors offer several advantages as compared to other technologies in terms of their relativelysmall size, lightweight, high survivability in extreme environments, inexistence of electrical signal at the sensor head, immunity from electromagnetic interference, having a remote distance between signal generation and detection, possibility of multiplexing as well as demonstrating high sensitivity. Therefore, several optical fiber liquid level sensors with differing approaches have been extensively developed and applied including liquid level sensor based on the fiber grating [1][2][3][4], fiber interferometry sensing [5][6][7], multimode interference (MMI) scheme [8][9][10] and fiber bend configuration [11,12].…”

Erbium Ring Fiber Laser Cavity Based on Tip Modal Interferometer and Its Tunable Multi-Wavelength Response for Refractive Index and Temperature

“…The appearance of other lasing modes was evident as the temperature increased because of the modal competitions was similar for all the lasing modes involved. It is well recognized that fiber-optic interferometers exhibit a suitable sensitivity for refractive index and temperature variations [44]; however, the ring laser cavity represents an alternative method to extract phase information [1][2][3][4][5][6][7][8][9]. In analyzing peaks P2, P3, and P6, the following thermal-wavelength relations can be expected: 21.01 pm/°C (P2), 16.99 pm/°C (P3), and 16.97 pm/°C (P6), as well as adequate linear responses of 0.96306 (P2), 0.99507 (P3), and 0.9890 (P6).…”

“…For several decades, the ability to generate tunable or switched multi-wavelength fiber lasers has been one of the focuses pursued by the fiber laser community. These lasers are associated with many reliable applications related to multi-wavelength spectra such as optical fiber sensors [1][2][3][4][5][6][7][8][9], spectroscopy systems [10], biomedical imaging [11], telecommunications [12], microwave photonics [13], and radio frequency optical domain systems [14]. These applications require achieving compact configuration, stable emission, narrow linewidth, and adequate spacing mode.…”