In-fiber Mach–Zehnder interferometer based on a Nd-doped double-clad fiber for switchable single and dual-wavelength EDF laser application

Abstract

We present an experimental study of a novel Mach-Zehnder in-fiber interferometer and its application for single and dual-wavelength operation of a ring cavity fiber laser. The proposed in-fiber interferometer, consisting of a segment of Nd-doped fiber spliced between two segments of standard single mode fibers, exhibits a wavelength periodical transmission spectrum with a period of 2.8 nm and a fringe contrast of ~0.8 dB. The Mach-Zehnder interferometer (MZI) is used as a spectral filter to obtain switchable single and dualwavelength operation of an Er-doped fiber laser (EDFL). Laser emission with laser lines spectral width less than 0.22 nm and wavelength separation of 2.8 nm corresponding to transmission spectrum wavelength period of the MZI is obtained. The stability of the dualwavelength operation of the EDFL is also discussed. The use of the proposed in-fiber MZI as a reliable, spectral filter to achieve stable single and dual-wavelength laser generation in a ring cavity fiber laser is experimentally demonstrated.

Reconfiguration of the multiwavelength operation of optical fiber ring lasers by the modifiable intra-cavity induced losses of an in-fiber tip probe modal Michelson interferometer

“…To the best of our knowledge, this work is the first to present a very simple method for reshaping the output emission in fiber lasers and controling the number of emission lines that can be implemented in ring cavity fiber lasers. In addition, the laser ring cavity can be altered for adaptation to a particular situation or application, for example by using another active medium, or even altering the ring cavity using methods that have already been proposed, such as changing the polarization light state in the ring cavity [34] or cooling the fiber in liquid nitrogen [35] to increase the lasing peaks of the modulated output laser spectrum. Another way to improve this work is by using a mirror in the planar face end of the tip probe to decrease the cavity losses caused by the reflection ∼96% and hence increase the laser gain and efficiency.…”

Wavelength switching and tuning of fiber lasers by using a modifiable intra-cavity filter based on a modal Michelson interferometer

“…However, these laser configurations need equipment which controls the combfilter spectrum, increasing the complexity and the cost of the laser system. Alternatively, there are also approaches where the reshaping in number of emissions of the laser output is based on controlling the polarization of the laser light circulating through the cavity [1,19,[25][26][27]. However, changing the polarization of light inside the laser cavity is not a repeatable process due to the difficulty to ensure the same position of the polarization controller for a determined polarization stage of the light.…”

“…Finding the correct position of a polarization controller involves some degree of trial and error. On the other hand, when the reshaping of the output laser by wavelength shift of the emissions is concerned, a number of works, instead of shifting the emission, they just switch the wavelength laser emissions [2,9,14,17,18,25,26,28,29]. However, switching of the emissions is just turning on and turning off the fixed laser wavelengths, rather than moving the emission at a preferred wavelength.…”

All-Fiber Laser Curvature Sensor Using an In-Fiber Modal Interferometer Based on a Double Clad Fiber and a Multimode Fiber Structure

“…The in-fiber device was constructed by fusion splicing of a SMF-MMF-DCF-SMF (SMDS) structure. The design of the optical device is based on a DCF to cause modal interference [ 18 , 19 ]. The DCF segment, with length of cm, is a homemade W-profile fiber with diameter of core, inner cladding and outer cladding of 7, 47 and 125 µm, and average RI of 1.459, 1.454 and 1.457, respectively.…”

“…Nevertheless it can be useful for multi-wavelength lasers design. Recently, we reported a switchable dual-wavelength erbium-doped fiber laser (EDFL) using a short wavelength period in-fiber MZI based on a DCF as spectral filter [ 19 ]. However, the design of fiber laser sensors by wavelength displacement requires spectral filters with long free spectral ranges (FSR) and high fringe visibility.…”