Opto-electronics components

  • Thread starter Gogsey
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  • #1
Gogsey
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This is not a homework question but for a project.

We are using a laser diode, one that you would normally find in a laser pointer to transfer information to a photo-transistor for a free space optical communications system.

Now I know the power output is around 5mW, but over a distance will we lose power as the light travels towards the photo-transistor? If so, how do you calculate the power at a certain distance, say 25 m or so?

Also, could someone also tell me the formula for calculating the spread of the laser light over a distance. This is so we know how much light is missing the photo-transistor and so we can correct this by using lenses to focus the light onto the photo-transistor?

Thanks in advance.
 

Answers and Replies

  • #2
ranger
Gold Member
1,685
2
Well it would still have to obey the inverse-square law. Doubling the distance from the source means a 1/4 reduction in power at the receiver end.
 

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