The fiber breakpoint measurement with OTDR can be divided into three steps: parameter setting, bai data acquisition and curve analysis. Manual setting of measurement parameters includes:
(1) Wavelength selection (λ):
Because different wavelengths correspond to different light characteristics (including attenuation, microbending, etc.), the test wavelength generally follows the principle corresponding to the system transmission communication wavelength, that is, when the system opens 1550 wavelength, the test wavelength is 1550nm.
(2)Pulse Width:
The longer the pulse width, the larger the dynamic measurement range and the longer the measurement distance, but the greater the blind zone in the OTDR curve waveform; the short pulse injection level is low, but the blind zone can be reduced. The pulse width period is usually expressed in ns.
(3) Measuring range (Range):
The OTDR measurement range refers to the maximum distance for the OTDR to obtain data samples. The selection of this parameter determines the size of the sampling resolution. The best measurement range is between 1.5 and 2 times the length of the fiber to be tested.
(4) Average time:
Since the backscattered light signal is extremely weak, statistical averaging is generally used to improve the signal-to-noise ratio. The longer the averaging time, the higher the signal-to-noise ratio. For example, the acquisition of 3 minutes will increase the dynamics by 0.8 dB compared to the acquisition of 1 minute. However, the acquisition time of more than 10 minutes does not significantly improve the signal-to-noise ratio. Generally, the average time does not exceed 3 minutes.
(5) Optical fiber parameters:
The setting of optical fiber parameters includes the setting of refractive index n and backscattering coefficient n and backscattering coefficient η. The refractive index parameter is related to the distance measurement, and the backscattering coefficient affects the measurement results of reflection and return loss. These two parameters are usually given by the fiber manufacturer.
After the parameters are set, the OTDR can send light pulses and receive the light scattered and reflected by the optical fiber link, sample the output of the photodetector to obtain the OTDR curve, and analyze the curve to understand the fiber quality.
Shenhuo Seiko Nanjing Communication Technology Co., Ltd as the leading manufacturer of Fusion Splicer and OTDR can provide many models for different requirements, including SM MM OTDR, PON OTDR and Mini OTDR. If you have any demands, please do not hesitate to contact us.
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