After the installation of fiber optic cabling system, it is needed to test the link transmission characteristics, including several most important test projects like link attenuation characteristics, connector insertion loss, return loss, etc. Following is a brief introduction of the measurements of the key physical parameters during the fiber optic cabling process.
The key physical parameters of fiber optic link：
Attenuation
1. Attenuation is the light power reduction in the fiber optic transmission.
2. Calculation of total attenuation of the fiber optic network: fiber LOSS is the ratio of the Power out of the fiber output end and the Power in of launched into the fiber.
3. The loss is proportional to the length of the fiber, so the total attenuation not only means the loss of fiber itself, but also reflects the length of the fiber.
4. Cable loss factor (α): In order to reflect the characteristics of the fiber attenuation, we introduce the concept of cable loss factor.
5. Attenuation measurements: As the fiber connected to the fiber optic light source and optical power meter will unavoidable take additional losses. Field test must carry on the test reference point setting (zero set). There are several methods for testing the reference point, these methods are mainly based on the link test object selection, in the fiber optic cabling system, since the length of the fiber itself is usually not long, so the test method will pay more attention to the connector and measurement of fiber optic patch cords, the method is more important.
Return Loss
The reflection loss, also known as return loss, refers to the backward reflection light relative to the ratio of the input number of decibels at the fiber optic connector, the return loss is larger the better, in order to reduce the reflection effect of light on the fiber light source and system.
The methods to improve return loss, try to use the fiber end surface is processed into spherical or oblique spherical is an effective way.
Insertion loss
Insertion loss is light signal in the optical fiber after through the connector, the output optical power relative to the input optical power ratio in decibels.
Insertion loss is smaller the better.
The insertion loss measuring method is the same with measuring method of attenuation.
In a word, to complete the measurement of an optical loss, a calibrated optical light source and a standard optical power meter is indispensable.
