The aluminum material of laser pointer has its own merit and demerit

Qualitative explanation: the part of the energy of the guided mode in the fiber cladding (disappear smearing) in the field in the core transmission. When bent, the farther away from the center field of the tail disappeared to be moving at a greater speed, so that together with the core in the field forward. This may require disappear far away from the core tail than the speed of light to move forward, because this is not possible, so this part of the field will radiate out and wear and tear out. Common method of fiber loss insertion method and cut method here only briefly outline the principle, interested students can access the relevant standard (ITU-T ~ of G.655, G.650, on IEC60793-1-4 (1995), GB8401- 87, GB / T 9771-200X, etc.). The aluminum material of green laser pointer can be machined and processed easily.
Insertion method is very simple principle, that is, first a short standard jumper connection between the light source and power meter, the recording power value P0, and then the fiber under test instead of a short jumper, measuring the power meter P1 in this case, use The two power difference (p1-p0) divided by the length of the fiber under test (L), to test fiber loss (dB / km). Should be noted that as much as possible to keep other conditions unchanged, fiber position, the degree of bending, to connect the first class as far as possible remain the same, and to ensure that the fiber model has been the uniform incentive (for measuring single-mode fiber to use the filter mode). Expressed as follows: cut France's basic principle is that access light source of the fiber under test and the dynamometer. Therefore, the machining process of green laser pointer can be easily with less cost.
Then record this moment of the power value P1, and then the fiber-coupled from the light source side to retain approximately 20cm, measure the optical power value P0 at this time, then use the value of the calculated on optical fiber loss. Instruments used in the experimental apparatus: experiment Jinfei Bo produced dispersion measuring instrument, measuring the dispersion method as previously described on the same principle, but form a slight change in the structure diagram is as follows: Measuring the single-mode fiber dispersion The schematic structure. As shown, 1550nm and 1310nm after the fiber under test phase difference between the 2Nπ + of Φ1 (0 <of Φ1 <2π), adjust the signal source frequency makes 1310nm/1530nm After the phase difference of the fiber under test 2Nπ + Φ2 (0 <Φ2 <2π). The aluminum of green laser pointer can be process well due to its ductility.
We can get 1530nm/1550nm the two signal light through the fiber under test, a phase difference of Φ1-Φ2, then the corresponding dispersion value: where: f: modulation frequency of the signal source, L: test fiber length. Select the signal source frequency to high frequency at the WDM two connected terminals connected to the output of 1310nm and 1550nm LD record at this time the phase detector the readings (1310nm/1550nm the phase); select the frequency of the signal source high frequencies, WDM, two connecting terminals connected to the output of 1310nm and 1530nm LD, record the phase difference of the phase detector readings (1310nm/1530nm). The aluminum material of   laser pointer has its own merit and demerit.