Polarization-maintaining fiber can maintain the polarization state of the beam propagation, and has a strong ability to resist environmental interference, so it is widely used in polarization-related fields.
In practical applications, if multiple polarization-maintaining fibers with polarization axes aligned with each other are uniformly installed on the array substrate by using V-Groove, a PM Fiber Array (PM Fiber Array) can be obtained.
High-density parallel transmission can be realized while keeping the polarization direction unchanged.
Polarized fiber arrays are mainly made of quartz, heat-resistant glass or silicon materials, with flat end faces or with a certain angle, and are mainly used in structures such as fiber optic sensors, communication systems, optical devices, and fiber lasers.
2.1 Optical fiber sensor
Fiber Optical Gyroscope (FOG) is an extremely important application of polarization-maintaining fiber in the sensing field.
Based on the Sagnac effect, the fiber optic gyroscope measures the rotation rate of the fiber optic ring by measuring the wavefront phase difference of light propagating in two opposite directions of the fiber optic ring.
Compared with traditional mechanical gyroscopes, fiber optic gyroscopes have the characteristics of no wear, short start-up time, long service life, high sensitivity, and large measurement dynamic range. They have a wide range of applications within civil navigation and transportation, military aviation, ship and guidance, and other fields.
2.2 Communication system
With the rapid development of optical fiber communication, the communication rate and capacity are further improved, and the communication system also puts forward higher requirements on the performance of the optical fiber. Therefore, polarization-maintaining optical fiber has gradually become an important part of the optical fiber communication system.
In the communication system, the pigtails of many devices use polarization-maintaining fibers, including widely used semiconductor lasers, erb-doped fiber amplifiers, and Raman amplifiers.
With the development of dense wavelength division multiplexing technology, it is necessary to further utilize polarization state multiplexing, so it is possible to write Bragg gratings on polarization-maintaining fibers.
2.3 Optical devices
In addition to being used as a pigtail of optical devices, polarization-maintaining fibers can also be used to prepare polarization-related devices using the characteristics of polarization-maintaining fibers.
For example, in the lithium niobate (LiNbO3) modulator used in telecommunication transmitters, the pigtail of the polarization-maintaining fiber can provide a stable polarization state and be aligned with the birefringence axis of the chip.
In the polarization interference filter, polarized light in different directions has different optical path differences after passing through the polarization-maintaining fiber. The interference effect of this polarized light can be used to realize the selection of light waves.
2.4 Fiber laser
Polarization-maintaining fibers are also widely favored in the design and production of lasers due to their unique properties.
PM fiber lasers are not only stable in structure, and less subject to environmental interference, but also have high output quality and good polarization performance and can achieve high-power laser output through beam combination.