Hi guys, Im Thava. Im working in optical communication. Currently I want to design a circuit to turn of couple of inputs to my laser.

Say I have a supply of 5V to two pins of the laser, anode and cathode (pin 1 and pin 2). And then a bias current to another pin (pin 3).

At some interval of time, I want to switch off the 5 V input to cathode and of course anode is grounded; also switch off the input bias current.

The switching off time should be in about 100 kHz, and it should be controllable. It should be in a way that, if I supply a pulse with pulsewidth of 100 kHz, it should switch off exactly at the falling edge of the 100 kHz. Is it possible?

And the switching time should vary, like I can always change the switching time.

I just need some suggestions, ideas and discussion. I have so many ideas on doing it, but cant choose a proper way, so I just need some guidance. It will be much appreciated!! Thank you.

 

Take a look at the PWM using 555 in the ebooks of this forum

links are located at the top of the page

 

A note on "on/off" times:

Pulse width modulation is the process of switching the power to a device on and off at a given frequency, with varying on and off times. These on and off times are referred to as "duty cycle".

 

Guys. A little bit more details would help. I will give more details now. The Cathode pin 2 should be supplied at 2.5 V. The bias pin 3 should be supplied from 40 mA to 120 mA, between this values.

Can someone give me a bit more details please. Thank you.

 

Use CD4016 IC, this is a Quad Bilateral Switch for Analog & digital signal.

 

Please provide the following information:

- datasheet of your laser
- is the bias input current or voltage driven?
- do you want to be able to control duty cycle or frequency or both?

please don't say "pulse width" of 100kHz. This makes only sense if we know the duty cycle. "Hz" is a frequency unit. Pulse width refers to time.

 

Hi Mercurius. Its a very good switch. But can you recommend similar switch that operates at minimum of 3 GHz? Cause the switch that you recommend only operates at MHz range.

Thank you very much!


Praondevou, thanks for your reply. I have attached the datasheet of my laser. Its bias current driven laser at pin 3, but the modulation electrical signal can be inserted in pin 12 as voltage. This laser is negative biased.

I want the switch to turn off the input signal to pin 3 and pin 12 at the interval of the pulse width. Sorry for referring it as frequency, it should be minimum of 40 us (pulse width).

Also, can anyone suggest a switch operates at minimum of 3 GHz range. Thanks!