Virgil,
I'll throw out a couple of basics in regards to the FDDI thingee [as to LAN cabling]:
1: Your idea of the lamp and photo voltaic cell isn't too far off! The pulses of light are created at the sending [Transmitting] end by an LED. The light is either in the Infrared spectrum or the Ultraviolet Spectrum [LASER diodes push UV light]. Light could also be in the visible white spectrum, but not sure if anyone uses this range.
On the Receiving end, the light pulses are "Picked Up" by either a Photo Doide or a Photo Resistor [Photo Diodes mostly used].
This type of interface is also used on other types of Opto-Isolators, like ones used in NICs [between the PC card and the LAN cabling] and on MODEMS [between the PC card and the Telco line. This establishes an Isolated link.
2: Typical setups would have Transciever arrangements - as do nearly all COM ports. So this makes each end have an LED and a Photo Diode.
3: The true power [watts] would be equal on what's put in and what's put out [if there's no losses]. Pump a Fiber with a 20 ma LED - driven at 22 VDC [giving 2 VDC for the Fowrard Voltage Drop of the LED] and this equals 0.4 watts. If this transforms into an equal lighting power, that is the total true power being pushed through the fiber pipe.
4: You are under the impression that Light and Electricity are both Electro-Magnetic Radiation ??? Where did you get that from? Couldn't have been from me!!
Now with the jokes over, you have figured CORRECT!!! [Time for a cigar!]
The Electro-Magnetic Radiation spectrum begins with VLF [Very Low Frequency] and this covers 0 to around 100 Hz. Audio Frequency "rolls over" the 100 Hz mark [beginning around 20 Hz] and runs thru 20Khz. Next is AM Radio stuff, then High Frequency, then VHF [covers the HAM radio guys, plus TV channels 2-13 and FM radio]. Next is UHF, then it steps into Microwaves [ovens and cell phones]. Next steps are the Infrared regions. After that comes the very narrow band of visible white light [tiny as compared to the other bands!]. This is followed by the Ultra Violet regions. After this comes the X-rays, Gamma Rays and Cosmic Rays.
Anyhow, just wanted to ramble this out!
Scott SET
