Light source for fiber optic lighting?

Can someone explain how a light source for a fiber optic light on audio gear would work? For example, the optical output on a DVD-player. There's a little red light burning away, but what is the light source? Can it ever go out?

edit: I rephrased my title and original post to (hopefully) word my question better.

 

This site should explain everything, Sam.

http://www.howstuffworks.com/question402.htm

 

This site explains the laser diode you are referring to within a CD/DVD player in more technically related detail.

http://home.mira.net/~gnb/mac-cdis/cd5.html

Actualy the whole site is interesting reading.

As to the diodes longevity, it all depends on the quality of the doping and assembly process the manufacturer used to create the luminescence of the diodes substrate.

 

Some cool stuff on both of those sights.

cosmkidebris: that link talked about the pickup laser. I'm more curious abou the source of light that emits light from the optical digital output[i/].

Cliff: so from that sight I get that that the source for fiber-optic lighting can be a laser? I was under the impressing that a bulb-type source was needed/used. Like when you have fiber-optics in a pool system, a bulb is the light source, correct?

 

I am guessing that I was looking into your question from a slightly different angle. When you posed the question pertaining a DVD player I assumed you were talking about the actual emitter/pickup used to read the software inserted into the player it.


Are you talking about the DVD player faceplate indicators? ie: on/off indicator, level indicators, mode indicators, etc. Generally you would use an LED to transmit visible light through a fiber.

 

Sam's talking about the light that eminates from the toslink connection jack.

 

A red light beam is used in Home Audio Equipment to transmit the audio signal. I'm *pretty* sure lasers are not used in any Home Audio Toslink connections, but I'm not a 100%.

 

The red light is definitely from a laser diode that transmits the audio signal to the deck for recording purposes. The IN jack has a photodetector attached to a seperate fiber which processes the laser diodes signal from the tape deck. The laser diode and the photodetector are mounted on the PCB inside the receiver as well as the deck. If you look at your deck it will have the same red light at the output jack like the receiver has. Laser diodes are very much like the common led, only you can control the on/off, or pulse of the laser diodes emmitance up to many Ghz in the right environment.

 

Good info. So does this mean that it never burns out? What are some other light sources for fiber optic lighting?

 

I would think that it would have to be a laser diode kind of setup no matter what. A regular light bulb of some kind, say an incandescent bulb, wouldn't work because you just can't "flash" that kind filament fast enough to do digital - to much persistance of light from such a source.

Sure, you can use the old 12V type bulb in your mid 70's fiber optic lamp, but don't expect it to send digital information.

And, a diode, using the proper voltage, can last a very long time. There is no real "burning off" of material like you do with an incandescent filament to the point of a "burn out". Too much voltage on a diode can cause a "burn up" though. And, I suppose age does get to an electrical component no matter what it is - eventually. Even properly set up LEDs will go out some day - but we're talking years.

Joel

 

Cool info guys. Thanks for the "schooling" on fiber op's, and thank you Sam, for starting the thread. It's a very interesting subject.

 

Sure! I just wanna learn, and this is a great place to share info. So to sum up: LEDs are the source for many fiber-optic lights. They last a very long time --shouldn't burn up!

 

I doubt that laser diodes (LDs) are being used over the short fiber runs toslink is designed to support. LEDs would be more than adequate in this application. LD are generally reserved for applications where the absolute maximum optical power is needed and the more complex circuitry they require is justified, such as long-run telecommunications; a toslink connection designed to cover a few feet certainly wouldn't require that kind of horsepower (this is not to say that they have never been used in this application, only that they shouldn't be necessary). Further, since fiber-optic systems generally operate in the infrared spectrum and lasers emit a only single wavelength, the fact that you can see the thing glowing red infers that it is probably a LED.

 

Makes sense, Gerry. Thanks for the clarification. So LEDs are 100,000 hour lifespan ususally?

 

You are right Gerry, I digress. Here is a data sheet referring to the type of LED used to transmit audio data.

http://www.toshiba.com/taec/components/Datasheet/TOTX176.pdf

 

This is great stuff, guys...thanks.



Ben