The main application principle of polarization maintaining fiber amplifier is shown in the figure below.

   The polarization-maintaining fiber structure devices in the figure include input coupler (polarization maintaining), isolator (polarization maintaining), WDM (polarization maintaining), erbium fiber (polarization maintaining), output coupler (polarization maintaining), and tail fiber of pump laser. This kind of structure is all polarization-maintaining structure, which makes the optical signal always keep the consistency of the polarization state in transmission.

   Polarization maintaining fiber devices are characterized by wide bandwidth, high return loss, high isolation, high extinction ratio, and solid environmental stability. Typical wavelengths include 980nm, 1064nm, 1310nm, 1480nm, 1550nm, etc. we can also provide C-band, L-band, and other broadband devices according to customer requirements. These devices are widely used in polarization-maintaining fiber amplifiers, polarization-maintaining fiber lasers, polarization-maintaining fiber sensing systems, high-speed communication systems, and test instruments and equipment for experiments.
   The polarization-maintaining fiber amplifier (MFA) is used to amplify the single-frequency laser with ultra-narrow linewidth, grating, and photodetector, which can be applied to the distributed optical fiber sensor for ultra long-distance and ultra wide-area monitoring. For example, in the application of fiber-optic hydrophone sonar array. Underwater hydrophone sonar array, optical fiber bottom array, and towed array using TDM and WDM technology. These sensor arrays can also be widely used in petroleum exploration and earthquakes.
   B-otdr (Chinese name "Brillouin scattering optical time-domain reflectometer") breaks through the traditional conventional OTDR attenuation test method. It can monitor the stress and strain of any optical fiber section in the whole process of submarine optical cable manufacturing, loading, and unloading, construction layout, operation, and maintenance, to directly reflect the stress condition of optical fiber in each process. It is of great significance to improve the manufacturing process of submarine optical cable. It is essential to find out the construction scheme and the hidden danger as soon as possible. Polarization maintaining fiber amplifier can also be used in b-otdr.