In order to improve the slop efficiency of the twins fiber, the coating process of the twins fiber was studied. Two kinds of twins fiber with different coating diameters were fabricated by using different coating molds. By building a 1080 nm laser amplification system, the slop efficiency of the twins fiber with different coating diameters was tested. Slop efficiency of the twins fiber with larger coating diameter was 61.2%. Compared to the twins fiber with small diameter, of which the slop efficiency was 58.6%, it increased by 2.6%. That meant appropriate coating process of the twins fiber could effectively increase the slop efficiency. When the slop efficiency was increased, the heat generated by the twins fiber as the pump changed into signal laser would decrease. This would reduce heat management pressure of twins fiber when it was used in optical fiber laser, and make the application of twins fiber have more broad prospect in high power fiber laser.
In recent years, the power level of laser outputting from twins fiber, being of pump unit fiber and gain unit fiber, is continuing rising. However, little report is focused on the pump coupling efficiency and thermal management on account of the distinctive waveguide of twins fiber. In this paper, the experiment study was launched on pump coupling efficiency and thermal management based on our previous work. To facilitate observing, two waveguides were designed as “cycle pump unit + octagonal gain unit” and “cycle pump unit + cycle gain unit”, while both gain units contained no doping core and the claddings were all 125 um approximately. It indicated that the pump power proportion between pump unit and gain unit was gradually changing with increasing of fiber length when the fiber was pumped from only one side of pump unit. The dynamic balance of pump power proportion could be obtained as the length of “cycle pump unit + octagonal gain unit” twins fiber is more than 4 m. By contrast, the balance point appeared earlier for “cycle pump unit + cycle gain unit” twins fiber before the length was up to 4 m. Further, the laser experiment was executed by using typical twins fiber that was consisted of one octagonal gain unit, containing Ytterbium (Yb) doped fiber core, and cycle pump unit. When the power was pumped into the fiber from the pump unit, the temperature of pumping point was obviously lower than conventional double cladding active fiber.
A novel kind of domestic twins fiber that consisted of active unit and passive unit was researched in this paper. The slop efficiency of the twins fiber was observed via various laser amplification testing systems, which were respectively established with two different pump wavelengths and two different numerical apertures of pump output fiber. The effect of both pump wavelength and numerical aperture on the slop efficiency of the twins fiber was analyzed during the experiment. After the laser amplification testing system was optimized, the slop efficiency of the twin fiber increased from 72.1% to 82.1%. The numerical aperture of the pump output fiber would exert a distinct influence on the slop efficiency of the twins fiber. Simultaneously, the method to improve the slop efficiency of the twins fiber and decrease heat generating in high power fiber laser system was suggested.
Polarization maintenance fiber with high birefringence is an important goal for the development of high power fiber lasers. There are different ways to achieve high birefringence, such as change shape of a fiber’s core and apply stress to a fiber’s core. In this paper, fibers with different ovality of elliptical core are fabricated and tested. On the other hand, stress type PM fibers are also made, including PANDA type fibers and bowtie type fibers. Their test results are compared and analyzed together with their structures. Generally, the bowtie type fibers has highest birefringence, while the PANDA fibers are with high birefringence and high production efficiency. Different application can choose different type of PM Laser fibers.
Protective fiber coating decides the mechanical strength of an optical fiber as well as its resistance against the influence of environment, especially in some special areas like irradiation atmospheres. According to the experiment in this paper, it was found that the tensile force and peeling force of resistant radiation optical fiber was improved because of the special optical fiber coating.
Absorption coefficient is a very useful feature for active fiber. In fiber laser system, the length of active fiber is chosen according to absorption coefficient. And the length of fiber can directly influence the feature of fiber laser. Therefore, how to obtain an accurate absorption coefficient is very important. Because fiber exists re-emission in typical absorption band pumped by power. It is difficult to accurately measure absorption coefficient. The absorption coefficients of Yb-doped double cladding fiber at 975 nm measured by several methods were compared. In conclusion, for the fibers with same length pumped by white light, the absorption coefficient is the highest when cutback only once. Meanwhile, when fibers with different length were measured by the same method, the absorption coefficient is inversely proportional to optical fiber length.
The power output of 2km and 8km 80μm selected cut-off wavelength single mode optical fiber was measured by 2.4W ASE fiber source at 1550nm waveband. The results show that obvious nonlinearity in 2km fiber does not occur by way of output power and spectrum. Slight nonlinearity is seen in 8km fiber. The power variation is small during the test of power stability with 1.28W input in 8km fiber.