free space pc link via usb port

[gloryloyalty]

hi all experts
would u mind giving help to me?
i'm student from myanmar & i'm now doing a project
a free space laser link has been built via rs232 serial port & so this port can't drive enough speed to optical link
then i've an idea of linking with usb port cos i'm so interested in usb concept
one thing i'd like to know is 'is it possible? '
cos usb port gives 2 signal lines(D+ & D-), how can laser represent that 2 signal lines
i think, laser can only represent one data line without WDM technology
it is not convenient to implement WDM device in here & so i can't imagine to learn this
then i've a strong wish to build simple laser link via usb protocol
any suggestions are warmly welcome
thankz in advance
gloryloyalty

 

[farhada]

Hi gloryloyalty,
In order to use the USB, you need to have a USB device, a micro controller or an IC that handled the USB communication on the other side.

It is almost the same way you communicate with a device using the RS232, but a little bit more complicated.

One of the companies who make USB devices is the FTDI, you can find a lot of information about their components on their web site http://www.ftdi.co.uk

You can also make a search on this site for books and articles about the USB to get more information about it.

Best regards,
/Farhad A.
PS. I hope people in your country were not badly affected by the Tsuname and the earthquake.

 

[Mfaham]

Hello
can you please tell me how i can connect the serial port from the transmitting computer to the laser (using Max chip) or what?

 

[farhada]

It depends on what you mean by laser, if you mean REAL laser then maybe someone else can help you,

If you want to use a LED laser then you can look at:

**broken link removed**

And you know, next time do a simple SEARCH before coming here and ask these kind of questions, it is really amazing 20 seconds later I have the answer, but you did not do the same before asking,

Cheers,
/Farhad

 

[spookysr]

hi all experts
would u mind giving help to me?
i'm student from myanmar & i'm now doing a project
a free space laser link has been built via rs232 serial port & so this port can't drive enough speed to optical link
then i've an idea of linking with usb port cos i'm so interested in usb concept
one thing i'd like to know is 'is it possible?
cos usb port gives 2 signal lines(D+ & D-), how can laser represent that 2 signal lines
i think, laser can only represent one data line without WDM technology
it is not convenient to implement WDM device in here & so i can't imagine to learn this
then i've a strong wish to build simple laser link via usb protocol
any suggestions are warmly welcome
thankz in advance
gloryloyalty

A optical link (laser) can represent 2 or more signal lines using audio FSK (frequency shift keying). However, you 're-inventing the wheel' is pointless when there is already RS232 serial ports and telephone modems. If you can't get a USB modem then get a Kensington Multi-Function Port Replicator (K33232) and connect it to your USB port. Now take the serial signal from the DB9 serial port and connect it to a standard 56k telephone modem. The audio FSK signal that comes from the modem's output (telephone line) can be used to AM (amplitude modulation) modulate a standard laser diode via a audio transformer. However a pulse modulation scheme will be less harmful to the laser diode. You'll need the same setup on the laser detector side (free space receiver) and you'll need to run a standard Windows terminal program like HyperTerminal. However, if your PC/laptop already has a serial port (which most modern ones don't) you wouldn't need the USB port. Technically you can modulate the laser even higher than this using a Ethernet configuration but I'd think you'd need a full-duplex 2-way laser link for it to work right.