The working principle of OTDR (Optical Time Domain Reflectometer) is based on the time-domain reflection characteristics of light. It determines anomalous points in the fiber by emitting a series of short pulse optical signals into the fiber and measuring the time delay and intensity changes of the reflected optical signals. OTDR utilizes Rayleigh scattering and Fresnel reflection to characterize the characteristics of optical fibers.
Working principle of OTDR
Transmitting optical pulses: OTDR sends short pulse optical signals to the tested fiber through optical fiber. These light pulses will encounter scattering and reflection due to the properties of the fiber itself, connectors, junctions, bending, or other similar events when transmitted in the fiber.
Receiving reflected signals: The reflected and scattered optical signals are returned to the OTDR port, received by the photodetector, and converted into electrical signals. These signals are displayed on the screen, with the horizontal axis representing distance and the vertical axis representing light intensity.
Data processing: OTDR compares the returned signal with the transmitted pulse, calculates the response data, and displays the relevant curve on the screen. By analyzing these curves, information such as the length, loss, and breakpoint position of the optical fiber can be determined.
Application scenarios of OTDR
OTDR is widely used for testing various optical communication networks, including testing joint losses, fiber distances, link losses, fiber attenuation, locating breakpoints and endpoints, testing reflection values and return losses in optical fiber transmission systems. It can also establish the relative relationship between event points and landmarks, create data files, and archive and print data.
Components of OTDR
Laser: sends stable optical signals to the measured fiber.
Pulse generator: controls the transmission time of the light source and works synchronously with the data analysis circuit.
Directional coupler: couples the light emitted by the light source to the measured fiber, and couples the reflected light signal to the photodetector.
Light detector: converts the reflected light signal into an electrical signal.
Data analysis and display: Compare the reflected signal with the transmitted pulse, calculate the response data, and display the relevant curve on the screen.