Re: Diode lasers are better than LEDs for fiber optic-Why?

Eric R Snow wrote:
On Mon, 2 Oct 2006 15:50:35 -0700, "Bob May" <bobmay@xxxxxxxxxxx>
wrote:


Aside from the transmission problems so well stated by Louis, there is also
the ability to modulate the light. Diode lasers can be modulated to much
higher frequencies than the LED sources. The remote controllers for all of
the electronic equipment tend to be running about as fast as they really can
and that is only in the region of 500KHz to 1MHz range. Laser diodes can be
driven a lot faster than this.

Greetings Bob,
Thanks for the reply. Since diode lasers and LEDs are both diodes it
seems to me that they could both be modulated at the same speed. You
state this is wrong. What is it about diode lasers that makes them
behave this way? As an aside, I remember reading about lasers about 40
years ago when I was 10 years old. A scientist was quoted in the
article that lasers did indeed have some uses but were mostly a
laboratory curiosity. Today the uses for lasers appear boundless.

You can't paint all lasers or all LED's with the same brush. There is considerable overlap in the fastest LED's and the slowest diode lasers.
Still, multi gigabit per second lasers are common in the communications industry. I don't know if non-lasing diodes (leds) could be manufactured to work that fast, but there's no reason to develop them as the there's no commercial market for them. The vast majority of diode lasers are made for the communications and data storage market (CD/DVD). The LED market is primarily for interfacing to human eyes. Sure, there are uses for slow lasers and fast LED's, but that's not what drives their development.

Forty years ago few people believed that there was a market for computers in the average home either. Watch what the next 40 years brings!

.

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