DIY FTTx projects design: Optical Loss

Optical power budget

  Certain aspects must be taken into account when calculating optical power total loss for an FTTx PON solution, like:

FTTx Optical Power budget

FTTx Optical Power budget

  • Fiber attenuation
  • Splice loss
  • Connector (Adapter) quantity
  • Splitter
  • Length of fiber

  In actual projects, following is the example of different factors that cause optical power loss in a FTTx solution:

Name Avg. Loss (db)
Connector lossAdapter0.2
Quick Connection Connector0.4
Splice lossFusion Splicing0.1
Cable (Commonly G.625)1310nm0.36/Km

What is “Optical power budget”?

  The optical power budget in a fiber-optic communication link is the allocation of available optical power (launched into a given fiber by a given source) among various loss-producing mechanisms such as launch coupling loss, fiber attenuation, splice losses, and connector losses, in order to ensure that adequate signal strength (optical power) is available at the receiver.

FTTx optical total loss

FTTx optical total loss

  In optical power budget attenuation is specified in decibels (dB) and optical power in dBms.

Splice loss

Splice loss

  In addition to transmission loss, including those of any splices and connectors, allowance should be made for at least several dB of optical power margin losses, to compensate for component aging and to allow for future splices in the event of a severed cable.

Connectors and Splices loss

Connectors and Splices loss

Length of fiber (Transmission Distance):

  1. FTTH PON can support a transmitting distance of about 20 Km under a 1:32 splitting ratio, and about 10 km under a 1:64 splitting ratio.
  2. The length of fiber mainly depends on the optical loss. The higher the optical loss is, the shorter the transmitting distance will be.
  3. If fiber transmission distance is more than 2 Km, fiber splicing should be considered, or combined with other technology.
FTTH PON+EoC Solution

FTTH PON+EoC Solution

  For nodes in different distances we may use FBT splitter to distribute more optical power to a farther node and less optical power to a closer node thus making sure all the nodes get enough optical power.

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