“…Stable single frequency, single polarized fiber laser sources are required in the applications of coherent communication, lidar, high precision sensing, and gravitational waves detection [1][2][3][4][5][6][7][8], among others, because of their superior narrow linewidth, low noise, and high power. In the past two decades, The linear cavity with distribute Bragg reflective (DBR) structure made of fiber Bragg gratings (FBGs) was used to obtain stable single frequency output in the field of fiber laser [9][10][11][12][13][14][15][16].…”