Study of LED response in optical telecommunication networks using DPWM access technique

Light emitting diodes (LED) are usually the second choice optoelectronic devices for optical communications with moderate bandwidth efficiency and bit rates, compared to semiconductor lasers. Laser applications dominate the long distance communication networks. However considering the cost efficiency, LED seems to be a very good solution, especially in short distance communication networks. From the LED's response in applied electrical signals, obviously there is a limit in maximum transmitted bit rate, posing an upper boundary in the available amount of information transmitted by LED. The idea of multiple access technique using Digital Pulse Width Modulation (DPWM) is needed in order to cure the weakness of LED's bit rate efficiency. Combining multiple access with source coding allows the transmission of 4 Mb/s using normal 2 Mb/s PCM line over short distance communication links.