 # Why Is Return Loss Negative?

## What is return loss in fiber optics?

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..

## Why is return loss important?

Media impedance is measured by return loss. Return loss is the ratio of the reflected signal to the launched signal. … This is because the more signal is reflected, this means we are delivering less signal to the load. Signal reflection is due to the discontinuity of the transmission line.

## Why return loss should be less than 10 dB?

S11 is return loss of device, this parameter measures how much input power given to device is reflected back at input port. … S11 below -10dB means at least 90% input power is delivered to device and reflected power is less than 10%. This value is sufficient for many applications.

## Why VSWR should be less than 2?

The range of values for VSWR is from 1 to ∞ . A VSWR value under 2 is considered suitable for most antenna applications. The antenna can be described as having a “Good Match”. So when someone says that the antenna is poorly matched, very often it means that the VSWR value exceeds 2 for a frequency of interest.

## What is s11 parameter in antenna?

The most commonly quoted and usable parameter in regards to antennas is S11. S11 (return loss) represents how much power is reflected from the antenna, and hence is known as the reflection coefficient (sometimes written as gamma: or return loss.

## How does antenna reduce return loss?

By this research work, the return loss reduction can be achieved using double U – slot stacked patch technique using FR4 epoxy material in microstrip patch antenna which is fed by coaxial probe. the best return loss i.e. RL = -49.16 dB at resonate frequency Fr = 3.53dB is achieved by this design technique.

## What is the difference between insertion loss and return loss?

Return loss is a measurement of the light reflected back to the source at an optical interface. … Insertion loss is different from return loss, which refers to the measurement for the amount of optical power loss through a mated pair, the lower the insertion loss, the better the performance.

## How much return loss is too much?

If the return loss is 10 dB, 10% of the power is returned. While different systems have different acceptable return loss limits, 15 dB or better is a common system limit for a cable and antenna system.

## How can insertion loss be reduced?

Fixing links that have failed insertion loss normally involves reducing the length of the cabling by removing any slack in the cable run. Excessive insertion loss can also be caused by poorly terminated connectors / plugs. A poor connection can add significant insertion loss.

## What causes return loss?

There are two major causes of RL in a network: discontinuities and impedance mismatches. Discontinuities occur at connections where cable is terminated to plugs or jacks and within the plug/jack connection itself. A discontinuity can also occur if a cable is bent too much, kinked or otherwise damaged.

## What is return loss measured in?

decibels (dB)The measure of this reflected power is called as return loss. Return loss (RL) is the ratio of the reflected power to the incident power, in decibels (dB). A high return loss is a problem as it indicates a large amount of power is being reflected back.

## What is antenna losses?

The efficiency of an antenna is a ratio of the power delivered to the antenna relative to the power radiated from the antenna. … A low efficiency antenna has most of the power absorbed as losses within the antenna, or reflected away due to impedance mismatch.

## Is Return Loss positive or 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. A high return loss is a good thing and usually results in low insertion loss. Reflectance, which also measures reflection and is expressed in dB, is a negative number.

## Is high return loss Good?

Return loss is a measure of how well devices or lines are matched. A match is good if the return loss is high. A high return loss is desirable and results in a lower insertion loss. Return loss is used in modern practice in preference to SWR because it has better resolution for small values of reflected wave.

## Is s11 return loss?

In practice, the most commonly quoted parameter in regards to antennas is S11. S11 represents how much power is reflected from the antenna, and hence is known as the reflection coefficient (sometimes written as gamma: or return loss. … This accepted power is either radiated or absorbed as losses within the antenna.

## What does negative dB loss mean?

If we have loss in a fiber optic system, the measured power is less than the reference power, so the ratio of measured power to reference power is less than 1 and the log is negative, making dB a negative number. … Instruments that measure in dB can be either optical power meters or optical loss test sets (OLTS).