This powerful program is designed to effortlessly calculate optical loss based on the input of RX and TX power levels, measured in milliwatts (mW). Not only does it perform this calculation with precision, but it also goes the extra mile by validating the results against a predefined loss budget. With its intuitive interface and accurate calculations, this program is a must-have tool for any optical engineer or enthusiast.
Calculating the loss budget for a fiber optic link should be done as part of the initial design of the link. A loss budget will estimate the loss of the link to provide assurance that the link will support telecommunications equipment intended for use on the link. It should also be used to provide an estimated loss value to use when testing the link with a test source and power meter after installation to determine if the link has been installed correctly.
The following information is needed to calculate a loss budget:
- Length of the link, end to end, in meters
- Number of connections, including connectors on each end
- Number of splices
- Fiber type (singlemode or multimode) and attenuation coefficient at each wavelength of interest
In the table below, attenuation coefficients are given from TIA-568, which is considered the worst-case, and for typical industry results. The table below shows typical loss for each component in an installed link.
| Fiber Type | Wavelength (nm) | Max Attenuation Coefficient Per TIA-568 (dB/km) | Attenuation Coefficient (typical) (dB/km) |
|---|---|---|---|
| Multimode | 850 | 3.5 | 3 |
| Multimode | 1300 | 1.5 | 1 |
| Singlemode (Premises) | 1310 | 1.0 | 0.5 |
| Singlemode (Premises) | 1550 | 1.0 | 0.5 |
| Singlemode (Outside Plant) | 1310 | 0.5 | 0.4 |
| Singlemode (Outside Plant) | 1550 | 0.5 | 0.3 |
| Component | Max Loss Per TIA-568 (dB) | Typical Loss (dB) |
|---|---|---|
| Connection (2 mated connectors) | 0.75 | 0.3 (Adhesive/polish type), 0.5-0.75 (prepolished/splice type), 0.75 (single ferrule multifiber array) |
| Splice (fusion or mechanical) | 0.3 | 0.05 (fusion), 0.3 (mechanical) |
- Calculate the loss of the fiber
- Calculate the loss of all connections
- Calculate the loss of all splices
- Add all losses to get the total loss
Multiply the length of the fiber times the attenuation coefficient of the fiber at each wavelength of interest. Multimode fiber is calculated for 850 nm and 1300 nm. Singlemode fiber is generally calculated for 1310 nm for most premises applications and 1310 nm and 1550 nm for outside plant applications.
For example, multimode fiber at 850 nm:
- Estimated fiber loss = length in km X 3.5 dB/km (TIA Max Specification)
- or
- Estimated fiber loss = length in km X 3 dB/km (Typical Specification)
The loss of a connection is the loss of a joint created by mating a pair of connectors. Estimates should always include the loss of the two connectors on the end of the cable plant since they will be mated to reference cables when being tested. Count the number of connections and multiply by the estimated loss of each connection.
For example, a cable plant with 3 connections plus the end connectors:
- Total connection loss = Number of connections (5) X 0.75 dB (TIA Max Specification) = 3.75 dB
- or
- Total connection loss = Number of connections (5) X 0.3 dB (Typical Specification) = 1.5 dB
If the cable plant has splices, count the number of splices and multiply by the estimated loss of each splice. For example, a cable plant with 3 fusion splices:
- Total splice loss = Number of splices (3) X 0.3 dB (TIA Max Specification) = 0.9 dB
- or
- Total splice loss = Number of splices (3) X 0.05 dB (Typical Specification) = 0.15 dB
Add the losses calculated above:
- Total fiber loss in dB = (fiber loss) + (connector loss) + (splice loss)
Use these numbers as estimates for "pass/fail" limits for testing. If the field-measured loss is significantly higher than the calculated value, troubleshoot the installation.
python loss_calc.py --tx <transmit_power> --rx <receive_power> [--fiber_type <fiber_type>] [--wavelength <wavelength>] [--fiber_length <fiber_length>] [--num_connectors <num_connectors>] [--num_splices <num_splices>] [--json]--tx <transmit_power>: Transmission power in mW (required)--rx <receive_power>: Received power in mW (required)--fiber_type <fiber_type>: Fiber type: 's' for singlemode, 'm' for multimode--wavelength <wavelength>: Wavelength in nm--fiber_length <fiber_length>: Total length of the fiber in meters--num_connectors <num_connectors>: Number of mated connectors--num_splices <num_splices>: Number of splices--json: Output results as JSON
- Calculate loss and validate against loss budget:
python loss_calc.py --tx 10 --rx 5 --fiber_type s --wavelength 1310 --fiber_length 1000 --num_connectors 2 --num_splices 1- Calculate loss without validating against loss budget:
python loss_calc.py --tx 10 --rx 5- Calculate loss and output results as JSON:
python loss_calc.py --tx 10 --rx 5 --json- NECA301-16, Standard For Installing And Testing Fiber Optic Cables
- TIA-526-14, Optical Power Loss Measurements Of Installed Multimode Fiber Cable Plant
- TIA-526-7, Optical Power Loss Measurements Of Installed Singlemode Fiber Cable Plant
MIT License
Copyright (c) [2024] [Matt Ladewig]
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