Multiwavelength switching of Raman fiber ring laser incorporating composite polarization-maintaining fiber Lyot-Sagnac filter

Abstract

A multiwavelength switching laser is demonstrated by a precise and fast tuning of a composite Lyot-Sagnac comb filter based on multisegment polarization-maintaining fibers. Broadband multiwavelength output is generated by cascaded Raman Stokes waves between 1.12 and 1.58 microns in a fiber-ring cavity with a wave-division-multiplexed coupler. Theoretical and experimental analysis of stable multiwavelength output operation for various Raman gain fibers and the electro-optic switching and flexible space tuning of interleaved wavebands are performed.

Wavelength-Swept Cascaded Raman Fiber Laser around 1300 nm for OCT Imaging

“…Considering the interaction between the pump light and Stokes waves, the generation of the instantaneous Stokes intensity is proportional to the optical pumping power and the stimulated Raman gain coefficient [18][19][20][21]. With increase in the length of the HNLF, the stimulated Raman gain coefficient can proportionally increase; however, the increased fiber loss coefficient at the Stokes wavelength suppresses the generation of the instantaneous Stokes intensity.…”

“…Since each cavity round-trip across the HNLF is optimally induced from the pairs of the FBG mirrors at 1064, 1117, 1175, and 1240 nm, the required pump power to increase the Stokes intensity can be effectively reduced, as can be inferred from the coupled equations of the cascaded RamanStokes shift [21]. When we remove the coupled FBG mirrors and adopt a ring cavity feedback structure based on the 1064/1310 nm WDM coupler only, a higher pumping power of more than 3 W is required to generate the fourthorder Stokes waves [18]. Figure 3 shows the schematic of the wavelength-swept fiber laser based on the cascaded Raman amplifier.…”

“…The laser is coupled with the fiber ring resonance cavity via the 1064/1310-nm WDM coupler. Since the 1064/1310 nm WDM coupler exhibits a minimum crosscoupling ratio around 1064 and 1550 nm and a maximum cross-coupling ratio around 1310 nm, it is useful to combine the optical pumping beam at 1064 nm into the ring cavity and to induce the highest feedback efficiency around the 1310 nm region in the ring cavity [18]. In this research, linear cavity feedback using the pairs of FBGs is used to reduce the required pump power to shift from 1064 nm to 1310 nm, and the ring cavity feedback using the 1064/1310 nm WDM coupler is used to form a lasing cavity for the gain region around 1310 nm.…”

“…To increase the pumping efficiency, a 1064/1310 nm wavelength-division multiplexing (WDM) coupler and coupled FBG mirrors reflecting wavelengths of 1064, 1117, 1175, and 1240 nm were optimally used in a laser ring cavity. Cascaded Raman fiber lasers can form a convenient alternative gain medium in the 1310 nm region as well as other wavelength regions as they provide highly efficient architecture [18]. Figure 1 shows the schematic of the cascaded Raman amplifier for the 1310 nm gain region.…”

Analysis of the tunable asymmetric fiber F-P cavity for fiber strain sensor edge-filter demodulation

“…The ratiometric wavelength monitor has the advantages of the simple configuration, high-speed measurement, and no mechanical movement [5]. For the cost-effective interrogation technique, linearly wavelength dependent devices based on various optical mechanisms, such as the Fabry-Pérot (F-P) filter [6], wavelength division multiplexing (WDM) coupler [7], long-period fiber gratings [8], and Sagnac loop filter [9], have been intensively developed, but these techniques still require more improvements in the stability, flexibility, and multi-point sensibility [10].…”