PROBLEM:
Free-space optical systems are generally used for "last mile" communication and can operate at distances of several kilometers long as long as there is a clear line of sight between the sender and receiver, and the optical receiver can decode the signal of the information transmitted. IrDA is an example of short distance, low speed free space optical systems using infrared LEDs. The challenge is how to increase this communication link distance and reduce errors.

SOLUTION:
Infrared Data Association (IrDA), defines a physical standard in the way of transmitting and receiving data by infrared rays. This technology is based on light rays that move in the infrared spectrum. The IrDA standards support a wide range of electrical, computing, and communications devices; they allow bidirectional communication between two ends at speeds ranging between 9600 bit / s and 4 Mbit / s.

The solution that I suggest is to use a laser beam with iRDA technology to communicate great distances and the features are shown below:

1. light Intensity modulation is commonly used to encode the signal, although it has been shown in laboratory tests that phase and frequency can be modulated. In this solution frequency modulation will be used.
2. To avoid damage the receivers the signal strength is monitored by a PID controller. In this way, we will never have high energy signals on the receivers.
3. The receiver will be tested with phototransistors and/or LDR sensors, and that will be resistant to environmental corrosion.

APPLICATIONS:

1. Voice, data and video transmission in cities. In this case repeaters will be used in the mountains to achieve line of sight.
2. Satellite telecommunications.
3. Develop a model for digital telecommunications of space missions between planets and tested with a simulator, for example between the Earth and the Moon or between the Earth and Mars.

NOTES:

1. It could be said that these systems have disadvantages compared to traditional methods. However: a) it must be remembered that every communication system has to be tuned in, such as a radio or TV station; b) we also have to point the satellite antenna to receive a good signal; and c) a fiber optic systems need amplifiers of erbium-doped fiber, to extend link distances at significantly lower cost.
2. Currently I'm working with a prototype for the transmission of music with infrared light; and a prototype with a laser diode is a project for the future.