Fiber Optic Cable Single Disk Testing And Fiber Optic Cable Line Testing Need To Use Double Window?

Fiber optic cable lines and broadband access projects usually involve fiber optic cable single disk testing and fiber optic cable line testing, fiber optic cable line testing includes: relay section testing, user cable testing and so on. These test entries, some only need to use the test instrument 1 wavelength for testing, that is, single window testing, and some need to use 2 wavelengths respectively, that is, double window testing.

2 fiber optic cable single disk test

Fiber optic cable single disk inspection is part of the transmission index of the cable equipment before construction inspection, usually checking the length of the fiber in the cable, fiber optic loss and observation of fiber optic backward scattering curve whether there are abnormalities. If the cable is not before the construction of a single disk inspection, laying and installation of good transmission indicators found to be abnormal, it is difficult to define the arrival of the cable quality problems or due to irregularities in construction. Therefore, the main purpose of the optical fiber cable single disk inspection is to define the responsible party in the project when the cable line transmission index found to be abnormal.

Optical fiber used in the project in the fiber optic cable, in the factory have been tested many times before the transmission indicators, generally does not appear in one of the window attenuation is normal, and another window attenuation abnormalities. Therefore, the single disk inspection only need to use a single window test can be, test wavelength as far as possible to use the cable line to be used in the working wavelength or 1550nm wavelength.

Single-disk inspection of fiber optic cables generally use OTDR, OTDR connected to the pigtail through the V-groove fiber optic aligner and fiber optic cable core connection.

3 cable line test

Fiber optic cable line test is the completion of the fiber optic cable line or ODN link (hereinafter collectively referred to as fiber optic cable line) attenuation test, the relay section of the cable also needs to be polarization mode dispersion test. In the engineering design, the attenuation of the cable line is based on the cable fiber, connector (including into the end), passive components such as attenuation of the worst value of the calculation, the attenuation of the cable line is often better than the measured value of the design value is more (about 0.04dB/km). Therefore, project acceptance, can not be based only on a single window of the measured attenuation of the fiber optic cable line to meet the design requirements to determine the transmission index of the fiber optic cable line is good or bad.

Although the attenuation coefficient of G.652 fiber under the 1310nm window is higher than 1550nm about 0.14dB/km, but due to the macro-bending loss of optical fiber is more sensitive to long wavelengths, the current cable line in the common existence of 1550nm window of the line attenuation of the 1310nm over the situation, which is mainly due to the cable connector and into the end, the fiber bending radius is not in line with the requirements of the result. Therefore, in the fiber optic cable line test, it is necessary to carry out double window test comparison, in order to test the macro-bending loss on the whole line.

4 Recommendations for the test window

In the information and communication construction project budget quota, there are four categories of entries related to fiber optic cables and fiber optic cable line testing, namely: single disk test of fiber optic cables, relay section test, user fiber optic cable test and ODN link test.

(1) Single-disk inspection of fiber optic cables requires only single-window testing with an OTDR at 1550 nm wavelength or working wavelength;

(2) The relay section test should test the attenuation at 1310nm/1550nm wavelength (G.652D fiber) or 1550nm/1625nm wavelength (G.654E fiber) respectively, and compare the test results at different wavelengths;

(3) The subscriber fiber optic cable test shall use the 1550nm wavelength and compare the attenuation at the 1310nm wavelength at a ratio of not less than 10%;

(4) The uplink and downlink of the ODN link shall be tested using the corresponding wavelengths of the system (or the uplink 1310nm and downlink 1550nm wavelengths) respectively;

(5) When preparing the budget, the labor and instrumentation quotas for the double-window test of the relay section shall be multiplied by a factor of 1.8, but the labor and instrumentation quotas for the test of the subscriber fiber optic cable and the full test of the ODN link need not be multiplied by the factor.