What is reflection in OTDR?

What is reflection in OTDR?

Introduction: OTDR – Measurement Interpretation Basics The OTDR injects an accurately timed light pulse into the fiber and the optical detector observes the small proportion of light that is reflected backwards (backscatter) as the forward propagating pulse travels along the fiber being measured.

What is LSA loss in OTDR?

The OTDR uses the LSA to correct the loss measurement for the marker positions. The LSA uses its mathematical analysis to calculate the straight-line approximation of the slope of the fibers on each side of the splice and then extrapolates those straight lines to the loss location to calculate the splice loss.

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 does a non reflective event appear on an OTDR trace?

Non-reflective faults are not identified by the conventional OTDR analysis based on only OTDR trace because the faults generate the same OTDR waveform. 2(a), Fresnel reflection occurs, but there is no power reflected toward the OTDR because the reflected signal goes to orthogonal directions of the tilted end face.

What is the principle of OTDR?

An OTDR sends short pulses of light into a fiber. Light scattering occurs in the fiber due to discontinuities such as connectors, splices, bends, and faults. The OTDR then detects and analyzes the backscattered signals.

What is meant by reflection loss?

In telecommunications, reflection loss occurs on a line which results in part of the energy being reflected back to the source. This can occur: At a discontinuity or impedance mismatch, e.g., in a transmission line, the ratio of the incident power to the reflected power. Reflection loss is usually expressed in dB.

What is dB loss in fiber optics?

dB (decibel) In the case of fiber optic cable, we are comparing the power injected at one end of the cable to the power received at the other end. If the optical power injected was -20 dBm and the power received at the other end -21 dBm, then the optical loss of the link would be -20 – (-21) = 1 dB.

What is dB in OTDR?

Whenever tests are performed on fiber optic networks, the results are displayed on a power meter, OLTS or OTDR readout in units of “dB.” Optical loss is measured in “dB” which is a relative measurement, while absolute optical power is measured in “dBm,” which is dB relative to 1mw optical power Loss is a negative …

How do you calculate reflection loss?

It may be defined logically as: SE= Energy Loss by Reflection/Total MW received.

Why is return loss negative?

Return loss, which measures the amount of light reflected back toward the source, is also expressed in dBs and is always a positive number. Reflectance, which also measures reflection and is expressed in dB, is a negative number. High reflectance is not a good thing.

What is a non reflective event?

Non-Reflective Event. This event is characterized by a sudden decrease in the Rayleigh. backscatter signal level. It appears as a discontinuity in the downward. slope of the trace signal.

What can cause a reflective OTDR event?

A pulse of light reflected back to the OTDR. Caused by a connector, tight bend, or crack in the fiber. Small reflective events may actually be ghosts. If the reflection is not caused by a connector, inspect the cable for tight bends or damage.

When does an OTDR indicate a non-reflective event?

Non-Reflective Event Sometimes when two fibers are spliced together, the backscatter level at the splice point shifts up instead of down. At first glance this would appear to be a “gain” in power at the splice. The OTDR may even indicate a negative splice loss.

How are reflectance and Optical Return loss measured?

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. Reflectance At An Event

How does optical time domain reflectometry ( OTDR ) work?

Depending on temperature Depending on strain and temperature •In operation, an OTDR launches pulses of light into the line fiber of an optical network and monitors the backscatter signal as a function of time relative to the launch time.

Where does the OTDR Test at the end of the fiber?

The actual end of the fiber should be very close to the point measured by the right cursor. To increase your confidence in this location, take the OTDR to the other end of the fiber and test back to the break from the other side. It is possible that the other side of the break will reflect some light.