What is OTDR and its function?
An optical time domain reflectometer (OTDR) is a device used to precisely detect faults in an optical fiber link of a communication network. Its function includes generation and transmission of a series of high-speed optical pluses within the fiber.
What principle of fiber optic cable loss does the OTDR use for measurements?
scattering
The OTDR, however, uses a unique optical phenomena of fiber to indirectly measure loss. The biggest factor in optical fiber loss is scattering. In fiber, light is scattered in all directions, including some scattered back toward the source as shown here.
What is the main difference between TDR and OTDR?
Essentially an optical time domain reflectometer, OTDR is the equivalent of an electronic TDR, but for optical fibres. The OTDR operates by generating and injecting a series of optical pulses into a fibre.
What is attenuation in OTDR?
Attenuation Dead Zone (ADZ) is the minimum distance for an OTDR to detect a non-reflective event (for example, splice) following a reflective event. The attenuation dead zone depends on the pulse width, the reflectance, the loss, the displayed power level and the location.
What are the elements of OTDR?
Lasers and detectors are key elements in an OTDR. An OTDR comprises a microprocessor, a pulse trigger and generator, a laser diode, an optical coupler, a detector, an analog-to-digital converter and a display (Figure 1).
What is the preferred wavelength setting for the OTDR?
Generally speaking, 1625 nm is the preferred wavelength for monitoring legacy 1310/1550-nm systems, largely due to laser cost. The 1650-nm wavelength is recommended for CWDM, DWDM, XGS-PON, and TWDM-PON systems where the traffic wavelengths extend into the L-Band.
How does OTDR test fiber?
The process of running these tests requires the OTDR tool to input a light pulse into one end of a fiber cable. The results are based on the reflected signal that returns to the same OTDR port. Some of the light transmitted through the cable will scatter and some will be reflected and returned to the OTDR.
What is reflection in OTDR?
Reflectance Testing By OTDR The OTDR can measure the amount of light that’s returned from both backscatter of the fiber and reflected from a connector or splice, leading to two independent tests, reflectance and optical return loss.
What is dB loss in fiber?
This indicates how much power the light has as it moves through the cables. Since the real goal is to transmit 100% of the data, the most useful metric is how much of it gets lost in transit. This is called dB loss.
What is reflectance dB?
Reflectance is defined by the amount of light reflected compared to the power of the light being transmitted down the fiber. Thus a 1% reflectance is -20 dB, which is about what you get from a flat polished air gap connection, and 1 part per million would be -60 dB, typical of an APC connector.
What is OTDR wavelength?
OTDR test pulse width wavelength: Normally, it’s 850 nm on multimode fiber optic cable and 1,310 nm on single-mode—the shorter wavelength has more back-scatter, so the trace will be less noisy.
What is Ghost in OTDR?
‘ Ghosts are false reflective events and can be difficult to distinguish because they are nonexistent events in the OTDR trace. The most common cause of ‘ghosts’ is an ‘echo’ of light reflected back and forth multiple times between strong real reflective events until it is attenuated to the noise level.
What is return loss in OTDR?
Return loss is the amount of light reflected from a single discontinuity in an optical fiber link such as a connector pair. Return loss is also called reflectance. For perfect transmission, optical loss and reflected power should be zero.
How do I set OTDR parameters?
To select Manual OTDR mode, turn the rotary switch to AUTOTEST, press F3 Change Test; then select Manual. You can access these settings on the Fiber OTDR tabs in Setup. Tip: To see the settings used for an OTDR test, press F2 View Events on the OTDR Results screen, press F3 View Details; then press F1 OTDR Settings.
What is the working principle of OTDR?
Working Principle and Characteristics of OTDR. The Optical Time Domain Reflectometer (OTDR) is an essential tool used to test the integrity of fiber optic cables, which can be applied to evaluate the length of fiber cables, measure transmission and connection attenuation and to detect the fault location of fiber links as well.
How does the OTDR measure loss in optical fiber?
However, the OTDR uses a unique optical phenomena “backscattered light” to make measurements along with reflected light from connectors or cleaved fiber ends, thus to measure loss indirectly.
How do you overcome dead zones in OTDRs?
Dead zones can be overcome by connecting a long launch cable to the OTDR. Launch fibers place a necessary length of fiber between the OTDR and the actual fiber being measured, providing both the time and distance required for the OTDR to effectively measure the characteristics of the fiber being tested.
What is an OTDR (optical time-domain reflectometer)?
OTDR (Optical Time-Domain Reflectometer) is such a powerful test instruments for fiber optic cable testing: when used properly, it not only simplifies testing requirements, but also help to increase the reliability and value of the network. What Is an OTDR and How Does It Work?