How to modulate a laser diode with an analog RF signal at 1 Ghz range?

[bibo1978]

Laser diodes optical power is senstive for currrent in the diode usually they are linearily related over some range of current intensity, however Rf amplifiers o/p is usually voltage signal, although most laser diode applicaton are in digital communication where modulation is done by on-off of laser o/p but I wonder how can I modulate a laser diode with an analog RF signal in 1 Ghz range?

 

[springf2000]

Re: Laser RF modulation

use the analoge laser diode such as the optical fiber CATV,it is not new to use the laser diode to transmit the RF signal,you can not to use the output signal of the PA to drive the lasder diode

 

[bibo1978]

Re: Laser RF modulation

I know that I can't drive the laser diode with a PA, I want also to note that the laser diode will not be coupled to a fiber optic.

 

[phocon]

Re: Laser RF modulation

Laser diodes are biased. Around the bias, the behaviour of the laser diode is linear, so you can define (and measure) the impedance of the laser diode. After this, you can design an impendance matching circuit, to avoid impedance mismatch between the laser and the waveguide between driver and laser diode.

You can easily calculate the current and voltage relation, once the impedance is known.

 

[bibo1978]

Re: Laser RF modulation

Can I directly connect the laser diode through a bais tee, appling a dc on the other end of the tee I can use a CW-laser diode "which was my plan", is this possible or I need an appropriate matching?

 

[springf2000]

Re: Laser RF modulation

i know what is the probelm y meet,y donot know how to use the rf signal modulate the laser diode,or in other worda, y cannot know how to feed the rf signal into the laser diode,right?

 

[bibo1978]

Re: Laser RF modulation

yes much of it,
I want to modulate the RF signal, to a CW laser diode, as I mentioned my plan was to use a bias tee to introduce the DC-bias "thershold".
however I have a problem with matching the circuit, I dunno how to model the diode impedance, what I want to know is how the matching is done in this situation?
or if this is not the way the laser diode is modulated with RF-signal, I wanted to know how modulation is done in such situation??
in my current design I don't have to worry about thermal runaway I will just try to mount the diode on an appropriate heat sink, and the pwr will be quite small so I don't have to worry for now about thermal compensation circuit "although this may affect the modulation ratio but with this procedures I guess I don't have a lot to worry about" or so I hope.