how to calculate the loss budget for a plant fiber optic cable plant
TRANSCRIPT
HOW TO CALCULATE THE LOSS BUDGET FOR A PLANT FIBER OPTIC
CABLE PLANT
SECTION 1: DEFINITION OF TERMS
SECTION 2: LOSS BUDGET CALCULATION STEPS (SAMPLE)
SECTION 3: CALCULATION CASE STUDY
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
Cable operating system wavelength
@850nm
@1300nm
@1310nm
@1550nm
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 cable1310 0.5
1550 0.5
T586 A&B STANDARDSOPTICAL FIBER CABLE WAVELENGHT (nm)
MAXIMUM ATTENUATION (dB/km)
50/125um multimode850 3.0
1300 1.0
62.5/125um multimode850 3.0
1300 1.0
Single mode inside plant cable1310 1.0
1550 1.0
Single mode outside plant cable1310 0.4
1550 0.4
Connector & Splice loss
Connectors loss 0.75db
Splice loss 0.2db
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
SECTION 2: LOSS BUDGET CALCULATION STEPS
(SAMPLE)
STEP 1
CALCULATE THE FIBER ATTENUATION
LOSS
STEP 2CALCULATE THE
CONNECTOR LOSS
connector loss =number of connectors X the maximum loss value
STEP 3CALCULATE THE
TOTAL SPLICE LOSS
The number of splice x times the maximum loss value
STEP 4CALCULATE OTHER COMPONENT LOSS
if ANY
OTHER COMPONENT SUCH AS SPLITER,ATTENUATOR,
STEP 5CALCULATE THE PASIVE SYSTEM ATTENUATION
This is the addition of fiber loss + connector loss + splice loss + other components loss + safety buffer
STEP 6CALCULATE THE LINK
LOSS BUDGET
Receiver sensitivity - transmitter’s average output power, (in dBm.)
STEP 7VERIFY THE SYSTEM
PERFORMANCE MARGIN
Link loss budget - passive system attenuation
STEP 8DETERMINE THE
RECEIVER’S DYNAMIC RANGE
Receiver maximum allowable input level - receiver
sensitivity
STEP 9COMPARE
Determine the sum of the system’s performance margin and the safety buffer. The total must be less than the dynamic range.
SECTION 3: CASE STUDY
,
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).