How to calculate Link Loss Budget, Passive Cable System Attenuation, and System Performance Margin
How to calculate Link Loss Budget, Passive Cable System Attenuation, and System Performance Margin
Understanding these calculations is crucial to ensure reliable connectivity and optimal performance in Telecommunication infrastructure. Here’s a step-by-step guide on how to approach each one:
✅ Link Loss Budget (LLB)
Step 1 : Calculate System Gain
System Gain is the difference between the transmitter average power and the receiver sensitivity
Step 2 : Determine Power Penalties
Power penalties add up the loss values from Operating Margin, Receiver Power Penalty and Repair Margin :
✴ Operatin Margin : Loss due to variation in transmitter center wavelength, changes in the transmitter average power/receiver sensitivity due to age, and temperature changes within the operating range. If unspecified, use 2dB for LEDs and 3dB for Lasers.
✴ Receiver Power Penalty : Some manufacturers specify other penalties like dispersion, jitter, bandwidth, or clock recovery.
✴ Repair Margin : If the cable is vulnerable to accidental damage, allow for at least two splices. More splices may be needed if reroutings are anticipated.
Step 3 : Link Loss Budget
Subtract the total value for all power penalties from the system gain. The result is Link Loss Budget.
✅ Passive Cable System Attenuation
Step 4 : Calculate Optical Fiber Loss
Multiply the length of the proposed link by the cable attenuation (dB/km) for the optical fiber at the operating system wavelength.
Step 5 : Calculate Connector Loss
Add the individual attenuation values (dB) for every connector pair along the optical fiber route (excluding transmitter and receiver connectors).
Step 6 : Calculate Splice Loss
Add the individual attenuation values (dB) for every splice along the optical fiber route.
Step 7 : Calculate Other Component loss
Add the attenuation values (dB) for any other components (Passive Optical Devices like Splitters) contributing to losses in the optical fiber route.
Step 8 : Calculate Total Passive Cable System Attenuation
Add all values from Optical Fiber Loss, Connector Loss, Splice Loss, and Other Component Loss to get the Total Passive Cable System Attenuation.
✅ : Verify Performance : System Performance Margin (SPM)
Step 9 : Calculate System Performance Margin
The System Performance Margin is the difference between the calculated Link Loss Budget and the actual Passive Cable System Attenuation.
SPM = Link Loss Budget – Passive Cable System Attenuation
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Source: LinkedIn
Credits: Mr. Ron Michael Johny – RCDD® I DCDC®
