FAQ

The first category is the optical attenuation caused by the too small bending radius of the optical cable.

When bending the optical cable, the minimum bending radius cannot be exceeded.

1. Burial depth. Since the direct buried optical cable is directly buried under the ground, there must be a certain distance from the ground. With the help of the tension of the ground, the optical cable will not be damaged. At the same time, the optical cable should also be protected from freezing.

Before laying the optical cable, the construction and related personnel should be properly trained on the matters that should be paid attention to in the construction, such as the essentials of laying out methods and safety, and ensure that the construction personnel obey the command.

1. The solution to environmental factors. First of all, it is necessary to determine whether hydrogen loss occurs in the outgoing optical cable. If hydrogen loss occurs, the attenuation degree can be judged by calculation, and compared with the margin reserved in the previous optical cable design. If the attenuation degree exceeds the margin, it needs to be replaced. If it is within the margin range, it can be maintained by formulating a plan. If the attenuation is caused by the physical characteristics of the optical cable itself, that is, the change of its own parameters with temperature increases, it is necessary to perform a window test, calculate according to the curve, and compare it with the design margin. If it exceeds the margin, it needs to be replaced.

Optical fiber is widely used in the field of communication because of its specific performance. Although the construction level of optical fiber cable has been significantly improved with the improvement of construction technology, there are still natural and artificial problems. This paper mainly expounds the common problems and countermeasures of optical cable construction for reference.

1. What are the causes of noise in optical fiber communication systems? There are noise caused by unqualified extinction ratio, noise caused by random variation of light intensity, noise caused by time jitter, point noise and thermal noise at the receiving end, mode noise of optical fiber, noise caused by pulse broadening caused by dispersion, and mode distribution noise of LD. , the noise generated by the frequency chirp of the semiconductor laser and the noise generated by the reflection.

1. What is the birefringence of a single-mode fiber? There are two orthogonal polarization modes in a single-mode fiber. When the fiber is not perfectly cylindrically symmetric, the two orthogonal polarization modes do not degenerate. The absolute value of the difference between two orthogonal polarization modes is birefringence.

1. What is the blind spot of OTDR? What is the impact on testing? How to deal with the dead zone in the actual test? Typically, a series of blind spots caused by saturation of an OTDR receiver is called a blind spot.

Optical fiber is the abbreviation of optical fiber. It is a fiber made of glass or plastic. It can transmit optical signals to thousands of kilometers away. Hundreds of thousands of optical fibers are combined together to make a cable-like optical cable. , so the optical cable is composed of a certain number of optical fibers, and the outer sheath is wrapped with a protective layer, which not only improves the strength of the optical fiber, but also greatly increases the communication capacity.

1. What do 62.5/125, 50/125 and 9/125 refer to in optical fiber? Answer: 62.5/125 means the outer diameter of the core is 62.5µm, the outer diameter after adding the coating layer is 125µm, 50/125 means the outer diameter of the core is 50µm, and the outer diameter after adding the coating layer is 125µm, and 9/125 means that the outer diameter of the core is 9µm, and the outer diameter after coating is 125µm.

1. Optical fiber scattering loss The scattering inside the fiber will reduce the transmitted power and cause loss. The most important of scattering is Rayleigh scattering, which is caused by changes in density and composition inside the fiber material.

1. Classification of fiber loss Optical fiber loss can be roughly divided into the inherent loss of the optical fiber and the additional loss caused by the operating conditions after the optical fiber is made. The specific breakdown is as follows:

1. What is the nonlinearity of fiber? Answer: It means that when the optical power of the incoming fiber exceeds a certain value, the refractive index of the optical fiber will be nonlinearly related to the optical power, and Raman scattering and Brillouin scattering will occur, which will change the frequency of the incident light.

1. What are the two commonly used single longitudinal mode semiconductor lasers? Answer: DFB lasers and DBR lasers are both distributed feedback lasers, and their optical feedback is provided by distributed feedback Bragg gratings in the optical cavity.