500-1000 Mbps pulse counter
500-1000 Mbps pulse counter
(OP)
I have a laser generating a pulse every 20 nS. Occasionally it will generate an extra pulse, so I'll have a packet of two pulses repeating every 20 nS. The second pulse in the packet will have a random delay after the first pulse; successive packets will keep that same delay.
I want to make a pulse counter to detect this condition. A counter that can run at 500-1000 MHz will be adequate. What type of architecture do you recommend?
Is ECL still available? I'd only need the first couple of stages to run very fast, and then I could use slower logic.
What about a fast FPGA? I see some that clock over 500 MHz and others supporting 1.25 Gbps serial ports. It seems like a bit excessive, but keeping everything in one IC might be simpler.
Any other suggestions?
Z
I want to make a pulse counter to detect this condition. A counter that can run at 500-1000 MHz will be adequate. What type of architecture do you recommend?
Is ECL still available? I'd only need the first couple of stages to run very fast, and then I could use slower logic.
What about a fast FPGA? I see some that clock over 500 MHz and others supporting 1.25 Gbps serial ports. It seems like a bit excessive, but keeping everything in one IC might be simpler.
Any other suggestions?
Z





RE: 500-1000 Mbps pulse counter
ECL is very rare now. A lot of stuff is as fast or faster now with less electrical complications,(split supplies), and dramatically less power consumption.
A really small FPGA or possibly a CPLD would probably work well.
What are you going to use to convert these pulses to electrical pulses you can count and track? A diagonal glass plate(?) deflecting to what sensor that is fast enough?
Keith Cress
kcress - http://www.flaminsystems.com
RE: 500-1000 Mbps pulse counter
Concerning "ease-of-use" I disagree with Keith. ECL is nice because it has constant current consumption and thus does not make supply decoupling as difficult as with hard-switching logic like CMOS.
There is no problem running ECL on a positive supply.
Best Regards,
Benta.
RE: 500-1000 Mbps pulse counter
Keith Cress
kcress - http://www.flaminsystems.com
RE: 500-1000 Mbps pulse counter
RE: 500-1000 Mbps pulse counter
I have a high speed photodetector available that is tapping off a small portion of the laser power.
I believe the single supply ECL is called PECL. A voltage divider for the termination sets up the proper bias. I'll check that out.
Each pulse ends up with 50% of the energy, so the energy content stays the same. IF I had an extremely fast peak detector I could see the difference. A slower detector will see the same average energy.
I realized that only the first stage of a counter needs to run this fast. By the time I get to the second bit it will only be toggling at 25 MHz. Maybe an ECL flip-flop followed by a slower speed FPGA/CPLD is the trick.
RE: 500-1000 Mbps pulse counter
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Benta.
RE: 500-1000 Mbps pulse counter
RE: 500-1000 Mbps pulse counter
Are the pulses themselves the max power for the laser (extremely high power pulse, very low duty rate), or are these pulses merely tickles to keep the tube ready for a full blast? Is the main power supply creating the pulse using internal circuitry, or is it through an applied digital signal attached to the supply? Is this a high-voltage DC supply or RF-excited laser?
A leakage in the HV DC path might lead to an extra pulse from time to time as the energy builds up. Any signal leakage back to an external controller board could also lead to an extra pulse from time to time, particularly due to poor/incomplete grounding.
Dan - Owner

http://www.Hi-TecDesigns.com
RE: 500-1000 Mbps pulse counter
This is purely an optical effect from a cavity laser like this one. The pulses are from the laser. As I understand, this laser should passively mode lock to a single pulse stream, but sometimes supports a second pulse stream.
Thanks all!
RE: 500-1000 Mbps pulse counter
Keith Cress
kcress - http://www.flaminsystems.com
RE: 500-1000 Mbps pulse counter
RE: 500-1000 Mbps pulse counter
RE: 500-1000 Mbps pulse counter
Benta.
RE: 500-1000 Mbps pulse counter
http://ww
RE: 500-1000 Mbps pulse counter
Luckily this has dropped a bit in priority, so I'll keep exploring options like the MC10EL34 or the InPhi part. It looks like I may need to cobble a circuit together to test my proof of concept.
Z
RE: 500-1000 Mbps pulse counter
Keith Cress
kcress - http://www.flaminsystems.com