3.1.4 - Transceiver Signal Strength Issues

Flashcards about fiber optic cable attenuation and signal loss.

Attenuation

The loss of signal strength over the length of the cable, dependent on fiber type and wavelength.

Single Mode Fiber Attenuation

Up to 0.4 dB/km loss.

Multimode Fiber Attenuation

From 0.8 dB/km to 3 dB/km loss.

Connectors (Fiber Optic)

Typically assumed to be 0.75 dB loss per connector.

Mechanical Splices (Fiber Optic)

Around 1 dB loss.

Fusion Splices (Fiber Optic)

Around 0.3 dB loss.

Attenuation in Fiber Optic Cable

This is due to microscopic imperfections in the structure of the glass fiber and in the smoothness of the edge of the core, leading to some small fraction of the light within the core being scattered or absorbed.

Testing Attenuation

Can be tested using an optical source and optical power meter (or fiber light meter), which may be purchased together as a fiber testing kit.

Optical Link Budget (Loss Budget)

The amount of loss suffered by all components along a fiber transmission path.

Estimated Loss Budget

Calculated when planning the link and tested at deployment to derive an actual value.

Differences Between Estimated and Actual Loss Budget Values

May reveal an installation fault or some unexpected source of signal loss.

Loss Budget Must Be

Less than the power budget.

Power Budget

Calculated from the transceiver transmit (Tx) power and receiver (Rx) sensitivity.

dBm

Measures signal strength against a reference value, where 0 dBm is 1 milliwatt.

Margin Between Power Budget and Loss Budget

A safety factor to account for suboptimal installation conditions, aging, accidental damage (additional splices), and performance under different thermal conditions.

Typical Outdoor Plan Margin

At least 5 dB.