In frequency division multiplexers, such as analog radio and TV, the data is distinguished by IF (intermediate or intermodulation) frequency. TV uses 4.5 mhz, FM radio uses 10.7 mhz. In wavelength division multiplexers, digital signals (clock) can be the laser diode wavelength. It is both clock and data, if zero and one(in amplitudes of minimum and maximum intensity) is applied to the clock cycle. The clock is then synchronized to a slower real time computer, which reads the clock which is data, every few cycles. If you have 200 or 20,000 or 2,000,000 real time computers to read 200 or 20,000 or 2,000,000 cycles in sequence, you have enough time to decipher and compute the fast clock data coming thru. The synchronization frequency by phase lock, is the interceptor frequency used by the clock of the input to the real time computers; then software synchronization line up the real time computers in an orderly fashion. This is the fastest way and the greatest number of channels, in communication bar none.
Recent development of Asic and Risc core (DSP) of deep submicron technology can go as high as 4 ghz clock. Instead of intercepting ATM packets, it can actually intercept data bits of each cycle of laser diode output in square wave. The leading edge of the square wave is used for phase lock synchronization. The question is which material will make the fastest laser diode?
You can still increase channels via intermodulation frequencies and use analog data on the clock to transmit 640 x 480 pixels of page of tables. Use character recognition to read tables transmitted in graphics form. The joke is that one pig tail needs a house full of DSPs to separate all the millions of channels of data. This is the new business to be developed. Wireless could use frequency division multiplexers to get 3 million channels or more. Ultimate transmission technology is now being defined. |
