J. Eur. Opt. Society-Rapid Publ. 2026, 22, 54 Ó The Author( s), published by EDP Sciences, 2026 https:// doi. org / 10.1051 / jeos / 2026042 Available online at: https:// jeos. edpsciences. org
EOSAM 2025 Guest editors: Omar El Gawhary, Stefan Witte, Ignacio Moreno
Journal of the European Optical Society-Rapid Publications
RESEARCH ARTICLE
L-band dual-wavelength fiber ring laser with automated polarization stabilization and switching for remote sensing applications
Santiago Tainta 1, 2, Alvaro Salinas 1, Iñaki Janices 1, Uxue San-Miguel 1, Arturo Sanchez-Gonzalez 1, 2, María José Erro 1, 2, and Rosa Ana Perez-Herrera 1, 2, * 1 Department of Electrical, Electronic and Communications Engineering, Public University of Navarra, 31006 Navarra, Spain 2 Institute of Smart Cities( ISC), Public University of Navarra, 31006 Navarra, Spain
Received 30 January 2026 / Accepted 3 May 2026
Abstract. This work reports the experimental demonstration of a dual-wavelength L-band fiber ring laser for remote sensing applications. The system incorporates a polarization-sensitive semiconductor optical amplifier as the gain medium and two fiber Bragg gratings placed 25 km away from the laser cavity using standard single-mode fiber that serve both as wavelength-selective elements and sensing heads. Wavelength switching between single- and dual-channel lasing configurations is enabled by a simplified two-paddle motorized polarization controller. The system achieves optical signal-to-noise ratios exceeding 55 dB and power differences between lasing lines as low as 0.01 dB. To ensure long-term stability, an automatic control algorithm dynamically adjusts the polarization state in real time, compensating for environmentally induced polarization drift. The proposed setup provides a compact and robust solution for polarization-based wavelength switching in fiber lasers, with applications in the field of remote optical sensing.
Keywords: Booster semiconductor optical amplifier, Fiber Bragg grating, Fiber-optic ring cavity laser, Polarization-switchable laser, Remote sensing.
1 Introduction
The development of single and multiwavelength fiber-based lasers has been an active area of research for decades, not only as they can serve as optical sources in the C-band of optical fiber communication systems, but also because of their applicability in fields such as sensing or spectroscopy, among others. While mostly developed for the C-band, there have been several proposals also for the L-band( 1565 – 1625 nm), since their use in this wavelength range allows to increase the capacity of fiber links [ 1 ], the simplification and improvement of lidar systems [ 2 ], the extension of sensing systems to other contexts [ 3 ] and the application in spectroscopy systems [ 4 ]. An especially relevant example is the detection of carbon monoxide, carbon dioxide, methane, and other potentially harmful gases with absorption bands in in the 1 – 2 lm spectral region, which has a clear impact in the protection of people and infrastructures in the oil and gas industries, water treatment plants, landfills, and commercial or domestic environments [ 5 – 7 ]. One of the most obvious advantages of using optical technologies in this context, the safety they offer by avoiding potentially flammable components, is reinforced if the sensor
* Corresponding author: rosa. perez @ unavarra. es head can be placed at a distance from the rest of the components, especially if the wavelengths can be remotely switched in order to enable the detection of different gases simultaneously. Switchable L-band multiwavelength lasers have been previously proposed for such applications, primarily based on fiber ring schemes [ 8 ]. Erbium doped fiber, which is the usual gain medium at lower wavelengths, presents a reduced emission cross-section beyond 1.6 lm. As a result, achieving sufficient gain at these longer wavelengths requires either longer fiber or higher doping concentrations. Additionally, the strong homogeneous broadening gain that Erbium doped fibers present leads to strong mode competition and results in poor laser stability. Addressing this issue requires the use of more complex setups or additional stabilization techniques [ 9 – 11 ]. Semiconductor optical amplifiers( SOAs) are consequently an interesting option as gain mediainthiswavelengthregion [ 12, 13 ]. In order to enable wavelength selection within the laser cavity, different optical filters are usually included into the ring structure, such as Fiber Bragg Gratings( FBGs) [ 14 ], Sagnac filters [ 8, 15 ] or Mach-Zehnder interferometers [ 16 ], among other techniques. Wavelength switching is typically accomplished by modifying the polarization state within the cavity, altering the ring cavity losses and, consequently, modifying the gain spectral distribution.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License( https:// creativecommons. org / licenses / by / 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.