OTDR optical time domain reflectometer parameter setting skills

using OTDR optical time domain reflectometer, the measurement of optical fiber can be divided into three steps: curve of parameter setting, data acquisition and analysis. Artificial setting measuring parameters include:
1, choice of wavelength lambda: because of the different wavelengths corresponding to different features, such as attenuation, slightly curved, generally follow the test wavelength and system transmission communication wavelength corresponds to the principle of the system open 1550 wavelength, the test wavelength of 1550 nm.
2, Pulse Width, Pulse Width, Pulse Width, the longer the dynamic measurement range, the greater the measuring distance is longer, but blind area bigger in OTDR curve waveform; Short pulse injection of low light level, but can reduce the blind area. Usually said by ns pulse width cycle.
3, measurement Range Range: OTDR measurement Range is refers to the OTDR to obtain the maximum distance of data sampling, the selection of the parameters determine the size of the sampling resolution. The best measurement range of fiber length under test 1. 5 ~ 2 times the distance between.
4, the average time: after due to light scattering signal is very weak, generally USES the statistical average method to improve the signal-to-noise ratio, average, the longer the higher signal-to-noise ratio. Take for example, 3 min acquired will take 0 improvement than 1 min. The dynamic of 8 db. But more than 10 min for taking time to the improvement of the signal-to-noise ratio is not big. General average no more than 3 min.
5, fiber parameters, optical fiber parameter Settings including refractive index n and backward scattering coefficient n and backward scattering coefficient set of eta. Refractive index parameters related to the distance measurement, backscatter coefficient, reflection and return loss measurement results. These two parameters are usually given by the optical fiber manufacturer.
parameter Settings, OTDR can send light pulses and received by the reflected light scattering and optical fiber link, the photodetector output sampling, get the OTDR curve, the curve is analyzed to understand the fiber quality. Hope the above introduction can help you.