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G.654.E fiber is primarily deployed in long-haul lines. Long-haul lines often carry high-capacity DWDM systems. As mentioned in Reference 1, high-capacity DWDM systems typically have high input optical power, making them prone to fiber burn-out at bends. Therefore, the macro-bending performance of G.654.E fiber is particularly important.
The mode field diameter of G.654.E fiber is approximately 40% larger than that of G.652.D fiber. Intuitively, this would suggest that its macro-bending performance is weaker than that of G.652.D fiber. However, fiber manufacturers claim that the macro-bending performance of G.654.E fiber is comparable to that of G.657.A2 fiber. So, what is the actual situation?
Fiber Macrobending Performance Test
We found a section of 144-core optical cable with all cores made of G.654.E fiber (see Figure 1). Due to a lack of stripping tools, we cut 1.5 meters from the cable in Figure 1, extracted several fibers, and spliced with pigtails to both ends of the fibers for testing.
Macrobending loss was tested at 1550 nm and 1625 nm optical fibers, respectively. An insertion/return loss tester was used for the 1550 nm wavelength test, while a spectrometer was used for the 1625 nm wavelength test. Figure 2 shows the instruments used for the tests.
For the test molds with different outer diameters, we used pens, steel pipes, plastic pipes, and also wrapped foam tape around the plastic pipes to obtain larger outer diameters. Figure 3 shows the molds used in the test
The G.652.D fiber used for testing was a 0.9 mm outer diameter G.652.D patch cord. To ensure that the outer diameters of the G.652.D and G.654.E fibers were consistent, a 0.9 mm diameter hollow protective tube was placed over the bare G.654.E fiber. The appearance of the G.652.D and G.654.E fibers used for testing is shown in Figure 4.
The additional losses of three G.652.D fibers and three G.654.E fibers at different bending radii were tested. The test results at a wavelength of 1550 nm are shown in Figure 5. In the figure, D1, D2, and D3 represent different G.652.D fibers, and E1, E2, and E3 represent different G.654.E fibers.
It can be seen from the figure that the macro-bending loss of G.654.E fibers is significantly lower than that of G.652.D fibers. Among the three G.652.D fibers, two have macro-bending losses several times higher than the third fiber at a bending radius of 5 mm, which may be due to the different origins of these three G.652.D fibers.
The additional losses of three G.652.D fibers and three G.654.E fibers at different bending radii were tested. The test results at a wavelength of 1550 nm are shown in Figure 5. In the figure, D1, D2, and D3 represent different G.652.D fibers, and E1, E2, and E3 represent different G.654.E fibers.
As can be seen from the figure, the macro-bending loss of G.654.E fiber is significantly lower than that of G.652.D fiber. Among the three G.652.D fibers, two fibers have macro-bending losses several times higher than the third fiber at a bending radius of 5 mm, which may be due to the fact that these three G.652.D fibers are from different sources.
The test results at a wavelength of 1625 nm are shown in Figure 6. Comparing Figures 5 and 6, it can be seen that the macrobending loss of the optical fiber at 1625 nm is significantly higher than that at 1550 nm.
To avoid measurement discrepancies caused by inconsistent fiber sources, we commissioned a major domestic fiber optic cable manufacturer to test the macrobending loss of one G.652.D fiber and one G.654.E fiber. During testing, the fiber was loosely wound 5 turns in a mold. The test results are shown in Figure 7 (the measured value was divided by 5 to obtain the value after one loose turn). In the figure, D55 represents G.652.D at 1550 nm, E62 represents G.654.E at 1625 nm, etc. As can be seen from the figure, the macrobending characteristics of the G.654.E fiber from the same manufacturer are almost identical to those of the G.652.D fiber.
Conclusion
The test results above indicate that the macrobending performance of G.654.E fiber from the same manufacturer is basically consistent with that of G.652.D fiber, but significantly different from that of G.657.A2 (see Reference 2 for macrobending performance testing of G.657.A2 fiber). Macrobending performance varies among fiber products from different manufacturers.
Generally, G.654.E fiber exhibits better bending performance than G.652.D fiber (this conclusion may not be universally applicable due to limited sample size).
Current fiber standards only require testing of macrobending loss at a curvature radius of 30 mm for G.652 and G.654 fibers. Given the requirements of practical engineering applications, it is recommended that G.652 and G.654 fibers, like G.657.A type fibers, also include macrobending loss requirements at 15 mm, 10 mm, and 7.5 mm.
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