Infrared LED communication question

I built an IR communication system . the transmitter controlled by arduino and modulated in 38Khz. the reciever is also controlled by arduino (another one) and demodulting the transmitter signals. everything is great so far. now i want to enlarge the communication range up to 1 kilometer and even farther. how can i reach this range (not involving any optics - telescope and ect.) by replacing to a very powerful led?
or optics is necessary for this kind of ranges?

I doubt you would get it to work over that range without using optics. An IR LED powerful enough to be detected over 1Km would use a huge amount of power and be dangerous to be near. Common IR LEDs normally have a fairly wide beam angle to make it easier to target the sensor from a hand held unit and this spreads the available light energy over a wide area. The available light diminishes rapidly as the distance increases. The simplest optics you could try would be a car headlight reflector at each end of the link. Initially use a visible LED to find the focal point where the light is concentrated forward and copy the location to the receiving reflector and mount the receiver there. I still doubt you would achieve 1Km though.

Brian.

To get more than a few metres you will need some optics and a modest to high power LED.
Google UK nanowaves to see what can be done, in some cases with relatively simple equipment, and what you will need to cover a path of greater than a km.

If you get 2m at the moment, at 1 Km, the beam will be spread over 500 times in height and 500 times in width, so the energy density will have fallen by 1/500^2 = 1/250,000, that's the loss you have to make up! (and there will be additional attenuation due to water vapour in the air and other effects). Call it a cool million
Frank

Showing my age now..... I think there used to be a pirate 'radio' station in London in the late 1960s that used an IR emitter on a tower and people nearby received it using IR sensors. I think the trick they used (remember this is in pre-LED days) was to use a powerful incandescent lamp which was mounted in a cage. The cage was surrounded by two rows of horizontal blinds, one was fixed and the other attached to a large voice coil actuator. High power audio was fed to the actuator which made the mobile blinds open and close, rather like the cone of a loudspeaker would move backwards and forwards. As the gaps between the blinds opened and closed it varied the amount of light that was emitted into the surroundings. I'm not sure it was successful, or even last for long but it did make use of lateral thinking (pun intended) in an ingenious way. Instead of modulating the light source, it modulated an attenuator around it.

It may have worked for analog audio but obviously it isn't practical for anythng but the slowest of data streams.

Brian.

Here you can find which are your main limitations:

http://www.sonoma.edu/users/f/farahm....ieee.2.97.pdf

Hi everyone,

I want to use an IR laser diode to communicate with my TSOP 38Khz photodiode reciever for large distance (1KM) using optics.

can someone recommend on a good and foucsed IR laser diode for my type of work?

Not very practical, I suspect.

How easy would it be to focus the extremely narrow laser beam on a tiny tsop 1km away?

Why dont you consider RF instead?