SFP Power Budget Calculation

[HanifSaharudin1989]

Hi All, 

I'm new on designing the Fiber Optic link loss budget. Please help me understand very well about this calculation.

I confused on some calculation:-

1. How to know the SFP/SFP+ power budget? As per I google, (min Tx - min Rx) =  Power Budget. 

2. If we use a patch cord from the FO patch panel to SFP port at the switch, connector loss will be on the connector at a patch panel only or both sides?

Here some is a formula do the calculation:

Link Loss= [fiber length(km) x fiber attenuation per km] + [splice loss x # of splices] + [connector loss x # of connectors] + [safety margin]

If need sends data from A to B:

Range: 10km

SFP type use: GLC-LH-SMD

Cable Wavelength: 1310nm

Qty of Splices Loss: 6

Qty of Connector Loss: 8

Safety margin:3.0 dB

I have done some calculation, I'm not sure the calculation and this design can work or not.

Please help and advise.

Thanks 

Hanif Saharudin

[Tom Randstrom]

The attenuation of a 10km link of SMF @1310nm is .35/km = 3.5dB (vs 28.57dB in your spreadsheet). Most splics will be 0.05db each and connectors of <0.25ea. 3dB margin on a 10km link is probably excessive. 

[HanifSaharudin1989]

Hi Tom,

Thanks for your reply. I already update my spreadsheet as below. 

How to calculate the SFP power budget? As I found, I calculate the GLC-LH-SMD is 10.5dBm. (Min Tx- Min Rx).

We need SFP power budget higher that total link loss to ensure the connection successful right?

Correct me if I'm wrong.

Thanks.

[Tom Randstrom · Accepted solution]

You are correct, 10.5dB for this 1G LX SFP.  You're estimating link loss using very conservative values and you have a 3dB link safety margin.  There are quite a few connectors in the fiber path, which increases loss and potential for future issues.  The unneeded connectors could be changed out to fusion splices to reduce link loss. 

[HanifSaharudin1989]

Hi Tom,

Thanks for your reply.

My last question, is there have connector loss at fiber optic patch cord where connected to SFP device? (For connected to patch panel, I’m sure there have connector loss)

Thanks.