Birefringence Analysis of Polarization Maintaining Fiber and Research on Characteristic of All-Fiber Beat-Length Experimental Systems

Study on polarization temperature dependence of large mode field reverse polarization maintaining fiber coupler

“…When the pump laser high-order mode passes through the pump fiber tapered cone, it becomes the leakage mode. As shown in Figure 4a, the increase of the leakage mode leads to the gradual reduction of the transmission coupling efficiency of the pump fiber of the two models of LMFRPM-OFC [21][22][23][24][25] .…”

“…In the process of pumping laser transmission, the central signal large mode field PM fiber in the coupling area of the large mode field LMFRPM-OFC fiber bundle generates its own uneven thermal stress. During the coupling fusion process of pump fiber and large mode field PM fiber bundle with central signal, due to the uneven distribution of external thermal stress, the refractive index of fast and slow axes in the stress zone of large mode field PM fiber will change [22][23][24] . It can be seen from Figure 4b that the structure change of the stress zone of the PM fiber in the large mode field of the central signal caused by the non-uniform external thermal stress in the fusion coupling of the fiber bundle coupling area of the LMFRPM-OFC leads to the change of the refractive index of the fast and slow axes in the stress zone of the forward polarized laser output fiber; At the same time, the pump laser generates uneven thermal stress in the coupling area of the fiber bundle of the LMFRPM-OFC with large mode field.…”

“…The original stress zone of the forward polarized laser output PM fiber used in the two models of LMFRPM-OFC is different from the thermal expansion coefficient of the fiber cladding, and there is an inherent thermal stress between the etching damage PM fiber stress zone and the fiber cladding [21][22][23] . During the fusion and coupling process of the model 1 forward polarized laser output fiber, the etching amount of the fiber cladding of the model 1 forward polarized laser output fiber is very small, and there is very little inherent thermal stress damage between the stress zone and the fiber cladding.…”

“…Because the built-in stress bar has a fast axis and a slow axis, the refractive index of the fast and slow axis in the stress zone of the PM fiber changes due to the mismatch of the symmetric structure of the stress zone relative to the center of the fiber core, and then the fast axis transmission light in the stress zone is converted into slow axis transmission during the internal transmission of the signal laser fiber. The increase of splicing time will cause the symmetrical structure mismatch of the core center in the stress zone, resulting in the decrease of the reverse extinction ratio of the LMFRPM-OFC [21][22][23][24] , as shown in Figure 6. In…”