Questions about laser module

[gnu]

Hello,
Application context : Transmit modulated data (max = 500Khz) up to 100
meter (in both sun light and dark environment). I have no experience
using laser so finding the appropriate module is a hard task for me.

I found http://www.worldstartech.com/ut.htm wich privide a variety of
modules.

-How to calculate the phisical range of the module (or the max phisical
range)? How to calculate the attenuation of the laser beam ?

-Some of the "Laser's Operation" are "x Khz" modulation and others
provide Continuous wave. Do this mean that i cant send a square wave
with them ? Whats the difference between the continuous and the
modulated modules ? Can't we externally modulate the signals ?

-How can we know if the laser is Safe for Eyes ?

Thanks.

 

[Rene Tschaggelar]

Hello,
Application context : Transmit modulated data (max = 500Khz) up to 100
meter (in both sun light and dark environment). I have no experience
using laser so finding the appropriate module is a hard task for me.

I found http://www.worldstartech.com/ut.htm wich privide a variety of
modules.

-How to calculate the phisical range of the module (or the max phisical
range)? How to calculate the attenuation of the laser beam ?

You need some optics to get a sufficiently wide beam diameter.
Even though 5mm may be sufficient, something above 1cm is better.
Attenuation... Well the beam is certainly visible in good
conditions. I bad conditions, rain, mist, haze forget it.
Stay with visible light, this is simpler to align.

-Some of the "Laser's Operation" are "x Khz" modulation and others
provide Continuous wave. Do this mean that i cant send a square wave
with them ? Whats the difference between the continuous and the
modulated modules ? Can't we externally modulate the signals ?

How would you externally modulate ? Yes, it is doable, but costly.

-How can we know if the laser is Safe for Eyes ?

Below 5mW.

Rene

 

[gnu]

Hey,

Attenuation... Well the beam is certainly visible in good
conditions. I bad conditions, rain, mist, haze forget it.
Stay with visible light, this is simpler to align.

So, in good conditions (sun light), with 5mw, 1cm beam, is the lazer
able to reach 100 meters ? Is there anny relatioship between the laser
magnitude and the reached distance ? can we mathematically estimate that ?

How would you externally modulate ? Yes, it is doable, but costly.

The problem is that i dunno how these lazer module works, so i imagine
that each module is a simple lazer diode, not ? so what we see at the
output is what we gave as input ? Please correct my idea.

Below 5mW.

Thanks.
Nico.

 

[Rene Tschaggelar]

So, in good conditions (sun light), with 5mw, 1cm beam, is the lazer
able to reach 100 meters ? Is there anny relatioship between the laser
magnitude and the reached distance ? can we mathematically estimate that ?

It is calculateable. At least the power that propagates to
the destination. The reception is a matter of signal_to_noise.
With some modulation it should be doable. What is the data rate ?
500kBaud ?
The beam propagation is called 'gaussian beam propagation'
and describes how the beam widens as function of the distance.
From the gaussian profile you could calculate the power at
the receiver optics.

The optics is not trivial. The laser diode output beam has
different divergences in perpendicular axis.

The problem is that i dunno how these lazer module works, so i imagine
that each module is a simple lazer diode, not ? so what we see at the
output is what we gave as input ? Please correct my idea.

The laser module is a laser plus perhaps a driver. The driver is
included when the voltage is 5V or so and the bandwidth is
rather low, eg 100kHz. Without a driver, the laser diode is
able to provide much greater bandwidth. This assumes you're
going to provide a driver with whatever bandwidth.
A driver is basically a current supply that tracks the
temperature behaviour of the laser diode such that it never
burns out. And it modulates the current such that the maximun
specifications are not exceeded.

Rene

 

[gnu]

It is calculateable. At least the power that propagates to

the destination. The reception is a matter of signal_to_noise.
With some modulation it should be doable. What is the data rate ?
500kBaud ?

I want to send 16 bites data up to 500 Khz.

The beam propagation is called 'gaussian beam propagation'

I thaught it's someting like exponential.

and describes how the beam widens as function of the distance.
From the gaussian profile you could calculate the power at
the receiver optics.

What's the equation ? have you somme related links please ?

The laser module is a laser plus perhaps a driver. The driver is
included when the voltage is 5V or so and the bandwidth is
rather low, eg 100kHz. Without a driver, the laser diode is
able to provide much greater bandwidth. This assumes you're
going to provide a driver with whatever bandwidth.
A driver is basically a current supply that tracks the
temperature behaviour of the laser diode such that it never
burns out. And it modulates the current such that the maximun
specifications are not exceeded.

So, if i take a laser module (continuous wave), what will i get in the
output if i give a square signal as input ?
Thanks.
Nico.

 

[gnu]

Hello,

It is calculateable. At least the power that propagates to
the destination. The reception is a matter of signal_to_noise.
With some modulation it should be doable. What is the data rate ?
500kBaud ?

What do you mean by some modulation ? How the laser model (signl/noise
equation) looks like ?
Thanks.