This document provides information and steps to calculate a fiber cable link loss budget. It defines key terms, lists standard fiber attenuation values, and common connector and splice losses. It then outlines the 9 steps to calculate a loss budget, including fiber attenuation loss, connector loss, splice loss, passive system attenuation, link loss budget, performance margin, receiver dynamic range, and ensuring the total margin is less than the dynamic range. Finally, it provides a case study example to demonstrate calculating the loss budget for a specific fiber link.

2. LOSS BUDGET
CALCULATION OF FIBER
CABLE LINK

3. SECTION 1: DEFINITION OF TERMS
SECTION 2: LOSS BUDGET
CALCULATION STEPS (SAMPLE)
SECTION 3: CALCULATION CASE STUDY

4. SECTION 1
Definition of terms
• FIBER ATTENUATION LOSS :this is an intrinsic
loss of signal over distance
• CONNECTOR LOSS : loss recorded as a result of
connectorisation
• SPLICE LOSS : loss recorded as a result of cable splicing
• LINK LOSS : the difference of the signal recorded on a link
• TRANSMITTER : the electronics that inject light into the
fiber cable
• RECEIVER SENSITIVITY : This is the lowest optical signal that
can be detected by the receiver

5. Cable operating system
wavelength
@850nm
@1300nm
@1310nm
@1550nm

6. EIA/TIA STANDARDS
OPTICAL FIBER CABLE WAVELENGHT (nm) MAXIMUM ATTENUATION (dB/km)
50/125um multimode
850 3.5
1300 1.5
62.5/125um multimode
850 3.5
1300 1.5
Single mode inside plant cable
1310 1.0
1550 1.0
Single mode outside plant cable
1310 0.5
1550 0.5

7. T586 A&B STANDARDS
OPTICAL FIBER CABLE WAVELENGHT (nm)
MAXIMUM ATTENUATION
(dB/km)
50/125um multimode
850 3.0
1300 1.0
62.5/125um multimode
850 3.0
1300 1.0
Single mode inside plant cable
1310 1.0
1550 1.0
Single mode outside plant cable
1310 0.4
1550 0.4

8. Connector & Splice loss
Connectors loss 0.75db
Splice loss 0.2db

9. SPLITTER LOSS
SPLITTER RATIO 1:2 1:4 1:8 1:16 1:32
Ideal Loss / Port (dB) 3 6 9 12 15
Excess Loss (dB) 1 1 2 3 4
Actual Loss (dB) 4 7 11 15 19

10. SECTION 2: LOSS BUDGET
CALCULATION STEPS
(SAMPLE)

11. STEP 1
CALCULATE THE FIBER
ATTENUATION
LOSS

12. STEP 2
CALCULATE THE
CONNECTOR LOSS
connector loss =number of connectors X
the maximum loss value

13. STEP 3
CALCULATE THE
TOTAL SPLICE LOSS
The number of splice x times the
maximum loss value

14. STEP 4
CALCULATE OTHER
COMPONENT LOSS
if ANY
OTHER COMPONENT SUCH
AS SPLITER,ATTENUATOR,

15. STEP 5
CALCULATE THE PASIVE
SYSTEM ATTENUATION
This is the addition of
fiber loss + connector loss + splice loss +
other components loss + safety buffer

16. STEP 6
CALCULATE THE LINK
LOSS BUDGET
Receiver sensitivity - transmitter’s
average output power, (in dBm.)

17. STEP 7
VERIFY THE SYSTEM
PERFORMANCE MARGIN
Link loss budget - passive system
attenuation

18. STEP 8
DETERMINE THE
RECEIVER’S DYNAMIC
RANGE
Receiver maximum allowable input level -receiver
sensitivity

19. STEP 9
COMPARE
Determine the sum of the system’s
performance margin and the safety buffer.
The total must be less than the dynamic
range.

20. SECTION 3: CASE STUDY
,

21. USE THE FOLLOWING INFORMATION TO CALCULATE THE
LOSS BUGDET OF THE SPECIFIED LINK
• The system wavelength is 1300 nm.
• The fiber type is 50/125 µm.
• The average transmitter output power is -15.0
dBm.
• The receiver sensitivity is -31.0 dBm.
• The receiver’s maximum allowable input level is -
20.0 dBm.
• The subject cable has 2 ST connector pairs.
• The subject cable has 3 splices.
• The subject cable’s length = 9.81 km.
(use TIA/EIA maximum loss per connector pair as
0.75 and 0.3 per splice loss for the calculation).

22. CABLE ATTENUATION
LOSS
9.81 X 1.5 = 14.715dB

23. CONNECTOR LOSS
2 X 0.75 = 1.5dB

24. SPLICE LOSS
3 X 0.3 = 0.9dB

25. CALCULATE THE PASIVE
SYSTEM ATTENUATION
14.715 dB + 1.5 dB + 0.9 dB + 2.0 dB
= 19.12 dB
Passive System Attenuation = 19.12 dB

26. Calculate the link loss
budget
Rx(max) – Rx (min)
-10.0 dBm - (-33 dBm) = 23
dB
Link Loss Budget = 23 dB

27. Verify the system
performance margin
Subtract the passive system attenuation
from the link loss budget.
23.0 dB - 19.12 dB = 3.88 dB
System Performance Margin = 3.88 dB

28. Determine the receiver’s
dynamic range
Receiver maximum allowable input
level - receiver sensitivity
-20.0 dBm - (-33.0) dBm = 13 dB
Receiver’s Dynamic Range = 13 dB

29. Determine the sum of the
system’s performance
margin and the safety
buffer.
The total must be less than the
dynamic range.
3.88 dB + 2.0 dB = 5.88 dB < 13 dB

30. INTERPRETAION
• Since the received signal
(19.12dB) is less than the
receiver dynamic range
(23dB) , the fiber electronics
(Tx, Rx equipment) in this case
study is suitable to handle this
cable link

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