In optical time-domain reflectometry, a blind zone is an area of the measurement range in which the reflection or attenuation characteristics of an optical fiber cannot be accurately measured. This is due to the limitations of its measurement technique and the physical properties of the optical signal propagating through the fiber. Although it is not possible to completely eliminate blind zones, there are several ways to minimize their effects:
1. Reducing the pulse width: Increasing the peak power of the pulse and reducing the pulse width can improve the resolution and measurement capability of the OTDR, thereby reducing the blind spot. Shorter pulse widths provide higher temporal resolution, allowing the OTDR to detect reflected signals closer to the starting point of the measurement. However, too short a pulse width can lead to increased noise in the measurement signal, so there is a trade-off between signal quality and resolution.
2. Using event superposition: Event superposition is a method of improving the optical time domain reflectometer measurement resolution and blinding by taking multiple measurements and superimposing fiber reflections and attenuation. By overlaying multiple measurements, reflected signals from farther away can be enhanced and the effects of blind spots can be minimized. This technique requires a stable fiber connection and maintaining the same environmental conditions and measurement setup.
3. Using forward scattering compensation: Forward scattering is a phenomenon in which the scattered signal in the fiber propagates towards the OTDR detector during the measurement. Forward scattering can mask reflected signals in the distance, resulting in blind spots. The use of forward scattering compensation techniques can reduce the interference of forward scattering on the OTDR, thus improving the sensitivity and accuracy of the measurement.
4. Reasonable selection of measurement parameters: Selecting appropriate measurement parameters, such as fiber length, sampling points and averaging times, can optimize the blind zone. According to the actual situation and demand, reasonable adjustment of these parameters can improve the resolution and sensitivity of the measurement, thus reducing the impact of the blind zone.
