subject: photo] On The Optical Fiber Splice Loss Testing, And Analysis [print this page] Author: Shu Weiming / China Railway 24 Bureau of Nanchang Telecommunication Company
Abstract: This paper describes the causes of optical fiber splice loss, fiber splice loss Test The principle and application of several test methods and calculations, a systematic exposition of the optical fiber splice loss testing of the scientific method.
Keywords: Fiber OTDR splice loss Fiber splice loss performance of optical fiber communication system in an important parameter, the value of the size of the loss of optical transmission system directly affects the overall transmission quality, Cable Construction and maintenance of test, test and analysis using the scientific method to improve the quality of the construction and maintenance of fiber optic cable connecting Care Workers As extremely important, particularly in the further study of long wavelength optical communication performance of single-mode optical fiber, transmission attenuation, precision and maintenance should have some practical significance.
An optical fiber splice loss analysis
1, fiber splice loss causes 1.1 intrinsic loss Intrinsic loss is a natural fiber material loss into the fiber preform after drawing determined that this loss can not be avoided, causing fiber intrinsic loss is mainly due to scattering and absorption, scattering is due to material density uneven generated Rayleigh scattering, absorption is mainly fiber materials of impurities of certain wavelengths of light particles have strong absorption.
1.2 additional loss optical fiber
Additional loss is the loss resulting from fiber-forming, mainly due to bending and microbending optical fiber produced by, in a cable and cable construction process will inevitably have to be bent, so it will produce an additional loss For single-mode fiber, docking of the two fibers, because the mode field diameter fiber core and Package Layer concentricity, roundness parameters of non-core is the difference between optical fiber splice loss will lead to the production of optical fiber in two completely aligned, and ignore the end-clearance cases, splice loss depends on the difference mode field diameter optical fiber , loss is calculated as follow: b = 20lg [1 / 2 (d1/d2 + d2 / d1)], d1 and d2 respectively, the two docking mode field diameter optical fiber, can be seen from the formula, the two-mode optical fiber butt field diameter equal (that is, d1 = d2), their splice loss b = 0.
2, affect the optical fiber splice loss reasons
Fiber splice loss affect the main reasons is the effect of fiber structural parameters and the welding machine welding quality, as well as a number of human factors and mechanical factors, such as optical fiber produced by host disk bend loss optical fiber Cutting Quality cross-section, transverse mismatch, vertical separation, axial tilt.
2, optical fiber splice loss test analysis
1, welding machine on the splice loss estimation theory
Welding machine follow through on the X axis and Y-axis fiber orientation of dislocation adjustment, the most hours in the welding axis displacement, and that can adjust the axis is called a core is open heart method, this method different the power detection, on-site can not know the exact splice loss values, in the adjustment process of the axis and the weld follow through Video camera The detection of the fusion core is the state of information, sent to the welding machine in the program, and then welding machine to calculate the value of splice loss, in fact, precisely, it is only shows the degree of optical axis aligned, does not contain Fiber itself is influenced by the inherent characteristics of the loss, while the OTDR test is backward scattering, which includes optical parameters of different forms of reflection loss, so the data shown in welding machine with the observation of optical fiber connecting section, than the rough estimate loss of fiber connecting point situation, not as a fiber splice loss of real value.
2, OTDR works Backscatter method is high-power narrow pulse of light into the fiber under test, and then detected in the same side to return back along the optical axis of the scattered light power, due to uneven density optical materials, their own flaws and mixed miscellaneous components uneven, when the pulse transmission through optical fiber, optical fiber along the length of each point will rise to Rayleigh scattering, which are part of the total numerical aperture angle into the fiber along the fiber axis reverse transfer to the inputs. Rayleigh scattering of light the same wavelength and the wavelength of incident light, the light scattering point of the incident light power and power is proportional to measure the return back along the optical axis Rayleigh scattering light power can be collected along the transmission loss of information, thus the measured optical attenuation.
Optical time domain reflectometer sends pulses into the input through the optical fiber, while the input to receive one of the Fresnel reflection light and Rayleigh backscattering light, and then become Telecommunications Number, with the time Oscilloscopes On display.
Fiber splice loss using OTDR test time, 1550nm wavelengths on the fiber-optic bending loss sensitive than 1310nm, the fiber splice loss test 1550nm wavelength should be selected to observe the laying of fiber optic cable and optical fiber connecting the optical fiber will bend due to excessive wear and tear caused by increased, but the use of light Optical Power Meter Entire transmission loss test should 1310nm and 1550nm wavelengths for the two sub-test. Optical fiber using OTDR monitoring
follow, there are two methods commonly used, first one is the one-way prior to the test method, OTDR fiber connecting in the direction of a joint point of testing, this approach to monitor, test points and connecting points is always fact they are just a cable length of the test Splice is more accurate, test speed, most of the cases to get a more accurate optical fiber connecting the loss value, but the drawback is the loss measured by the value of all single test data can not fully and accurately reflect the true optical loss values follow. As shown:
Figure 1 Optical loss test plan
Second is two-way prior to the test method, OTDR test points and connecting points on one-way monitoring is still the same layout as before, but they have to follow the direction of the best start to do loop end, that end will follow the direction of the beginning each beam tube were 22 short-fiber access, the composition of Central Hui Road, the addition of the loop point, so OTDR splice loss test can detect two-way value, with two-way OTDR testing prior to the fiber, the direction of the test results of two sometimes different, mainly due to fiber core diameter and relative refractive index are not the same (ie, different Brand Or different batches of fiber fusion), not only cause loss of fusion increases, will result in OTDR in both directions (A-ended to ended to A B-side or B side) of the measured values vary greatly, was welding when the two fiber the mode field diameter at the same time, because the mode field diameter of small Rayleigh scattering optical fiber transmission capacity than the large mode field diameter fiber strength, so when this
photo] On The Optical Fiber Splice Loss Testing, And Analysis
