CN-224231997-U - Multi-cladding erbium-ytterbium co-doped polarization-maintaining fiber

CN224231997UCN 224231997 UCN224231997 UCN 224231997UCN-224231997-U

Abstract

The utility model relates to a multi-cladding erbium-ytterbium co-doped polarization-maintaining fiber, which comprises a fiber core, a step layer, a stress area, a round inner cladding, a round outer cladding and a round organic polymer coating layer from inside to outside on the section of the fiber. Compared with the traditional erbium-ytterbium co-doped polarization-maintaining fiber, the utility model adopts a plurality of different end surface structural areas, increases a layer of low-refraction glass inner cladding, and can effectively reduce the interaction of the organic coating on the pump light, thereby inhibiting the aging of the organic coating during high-power output, improving the high-temperature tolerance of the fiber and reducing the burning risk of the fiber. Meanwhile, a step layer is added on the outer ring of the fiber core, so that the effective numerical aperture of the fiber core and the cladding is reduced, good beam quality can be ensured under the condition of improving the size of the fiber core, and the output power of the optical fiber is effectively improved. The erbium-ytterbium co-doped polarization-maintaining fiber is more suitable for long-term stable use under the high-power high-temperature condition.

Inventors

WANG FAN
HU LILI
YU CHUNLEI
ZHU YIMING
WANG MENG
ZHANG LEI
DONG HEHE
GUO MENGTING
WANG YAFEI

Assignees

中国科学院上海光学精密机械研究所

Dates

Publication Date: 20260512
Application Date: 20250609

Claims (8)

1. The multi-cladding erbium-ytterbium co-doped polarization-maintaining optical fiber is characterized by comprising the following components in sequence from inside to outside: The erbium-ytterbium doped fiber core (1) is used for conducting signal light in a 1.5-micrometer wave band; A step layer (2) which is coated on the periphery of the fiber core (1) and has a refractive index lower than that of the erbium-ytterbium doped fiber core (1) so as to form a first optical confinement structure; A pure quartz glass cladding layer (3) which is used for cladding the step layer (2) and is internally and symmetrically embedded with two stress areas (4) for providing polarization maintaining performance and inhibiting spiral rotation of the cladding layer; A fluorine-doped quartz glass cladding layer (5) which coats the outer surface of the pure quartz glass cladding layer (3) and has a refractive index lower than that of the pure quartz glass cladding layer (3) so as to form a second light confinement structure; An organic polymer coating layer (6) coating the outer surface of the fluorine-doped quartz glass cladding layer (5); The step layer (2) and the fluorine-doped quartz glass cladding layer (5) act together to restrict signal light into the erbium-ytterbium doped fiber core (1) and the pure quartz glass cladding layer (3), so that light absorption of the organic polymer coating layer (6) is reduced, and the problem of ageing of the coating under high power is solved.
2. The multi-cladding erbium-ytterbium co-doped polarization-maintaining fiber of claim 1, wherein the pure quartz glass cladding (3) has a circular structure and is concentrically arranged with the circular structure of the fluorine-doped quartz glass cladding (5), and the interfaces of the pure quartz glass cladding and the fluorine-doped quartz glass cladding are in seamless welding to eliminate bubbles and bright spots when a high-temperature rod is sleeved.
3. The multi-cladding erbium ytterbium codoped polarization-maintaining fiber of claim 1, wherein the stress areas (4) are circular and symmetrically distributed on two sides of the fiber core (1), and the ratio of the diameter of the stress areas to the diameter of the fiber core (1) is greater than 3, so that stress birefringence is enhanced and the absorption efficiency of pump light is improved.
4. The multi-cladding erbium-ytterbium co-doped polarization-maintaining fiber of claim 1, wherein the ratio of the diameter of the step layer (2) to the diameter of the erbium-ytterbium doped fiber core (1) is 1.8-3, and the light beam quality is ensured while the fiber core size is increased by reducing the effective numerical aperture of the fiber core.
5. The multi-cladding erbium-ytterbium co-doped polarization-maintaining fiber of claim 1, wherein the ratio of the diameter of the fluorine-doped quartz glass cladding (5) to the diameter of the pure quartz glass cladding (3) is 1.05-1.3, so that cladding light is effectively restrained and the welding interface is defect-free.
6. A multi-clad erbium ytterbium co-doped polarization-maintaining fiber according to claim 1, wherein the refractive indexes of the layers are strictly satisfied that the refractive index of the erbium ytterbium doped fiber core (1) is equal to the refractive index of the step layer (2), the refractive index of the pure quartz glass cladding (3), the refractive index of the stress region (4) and the refractive index of the fluorine doped quartz glass cladding (5), and the step refractive index distribution is formed to optimize the optical field constraint.
7. A multi-clad erbium ytterbium co-doped polarization-maintaining fiber according to claim 1, wherein the organic polymer coating (6) is thermally isolated from the fluorine doped quartz glass cladding (5) by physical contact and has a diameter larger than the fluorine doped quartz glass cladding (5) to provide mechanical protection.
8. A multi-cladding erbium ytterbium co-doped polarization-maintaining fiber according to any of claims 1 to 7, wherein when said fiber is used in a 1.5 μm band lidar system, the output power is not less than 50W and the continuous service life exceeds 10,000 hours.

Description

Multi-cladding erbium-ytterbium co-doped polarization-maintaining fiber Technical Field The utility model relates to the technical field of fiber lasers, in particular to a multi-cladding ytterbium erbium co-doped polarization-maintaining fiber. Background The erbium-ytterbium co-doped polarization-maintaining fiber with the wavelength of 1.5 microns has wide application in the field of wind-measuring laser radars, optical signals with the wavelength have remarkable advantages in the aspect of human eye safety, and the loss in the atmospheric transmission process is relatively low, so that the wind-measuring laser radars based on the erbium-ytterbium co-doped polarization-maintaining fiber with the wavelength of 1.5 microns have great application potential in the fields of meteorological monitoring, aerospace, wind power generation and the like. In order to effectively expand the detection distance of the wind lidar, further improve the accurate acquisition capability of the wind lidar on the remote target wind field information, and improve the output power of the optical fiber, the wind lidar is an important technical requirement. Higher output power means that the lidar can emit stronger signal light so that echo signals of sufficient strength are received over longer distances to enable accurate measurement of wind field parameters. However, under the operating condition of high power output, the long-term reliability of the erbium ytterbium fiber becomes a core element for restricting the quality and performance stability of the wind-sensing radar product. The conventional erbium-ytterbium co-doped optical fiber is relatively simple in structural design, and is usually obtained by directly coating an organic resin material on the outer surface of a pure quartz cladding layer as a protective layer. The structural design can possibly meet basic use requirements in a low-power operation environment, but the limitation of the structural design is outstanding in a high-power output scene. Because the organic resin material has higher absorption coefficient to the signal light with the wave band of 1.5 microns, when the leaked signal light with the wave band of 1.5 microns in the optical fiber is directly absorbed by the organic resin, the signal light can be quickly converted into heat energy, and the local temperature of the optical fiber coating is rapidly increased. Under the long-term continuous combined action of light and heat, the chemical structure and physical properties of the organic coating can change in a series of complex ways, and aging phenomena gradually occur. The mechanical property and optical property of the aged organic coating are obviously reduced, and the protection effect on the optical fiber is weakened. Along with the continuous aggravation of the aging degree, when the situation is serious, the surface of the optical fiber can possibly generate light leakage and bright spot phenomena. These light leakage and bright spots are not only the manifestation of the light energy loss in the optical fiber, but also the visual manifestation of the local overhigh temperature of the optical fiber. Once the local temperature exceeds the tolerance limit of the fiber material, there is a high probability of risk of fiber burnout. The optical fiber burnout not only can cause the laser radar system to work abnormally, but also can cause threat to peripheral equipment and personnel safety, thereby seriously affecting the long-term use reliability of the optical fiber laser in the high-power application fields such as wind-measuring laser radar and the like. Therefore, how to effectively solve the long-term reliability problem of the traditional erbium-ytterbium co-doped fiber under high power output becomes a key technical problem to be overcome in the field of fiber laser, and has a great significance for promoting the further development and wide application of wind-measuring laser radar technology. Disclosure of utility model The utility model aims to overcome the defects of the prior art, and provides a multi-cladding erbium-ytterbium co-doped polarization-maintaining optical fiber which can greatly reduce the absorption of an organic coating to signal light with a wave band of 1.5 microns so as to solve the reliability problem in the background. In order to achieve the above purpose, the present utility model proposes the following technical scheme: The multi-cladding ytterbium erbium co-doped polarization-maintaining optical fiber is characterized by comprising the following components in sequence from inside to outside: The erbium-ytterbium doped fiber core (1) is used for conducting signal light in a 1.5-micrometer wave band; A step layer (2) which is coated on the periphery of the fiber core (1) and has a refractive index lower than that of the erbium-ytterbium doped fiber core (1) so as to form a first optical confinement structure; A pure quartz glass cladding layer (3) which is used f