[Ronja] What about using a polarizer?

[Gregory Maxwell]

On Mon, Oct 20, 2008 at 5:40 PM, Kilian Kiekenap
<einer.aus.der.klasse at kilian-kiekenap.de> wrote:
> Hello,
>
> I often thought about how to make Ronja 100mbit. I think the main problem is
> to get the nrz-code over the optical link. So I thought it would perhaps be
> possible to use two transmitters with different polarization and two
> receivers which can receive them independently. So you could get four
> different symbols.

There can only be two totally orthogonal polarizations.

I do not believe that the available LEDs have a sufficiently flat
response beyond 20MHz.  So even a 2x gain from polarization division
multiplexing is not going to be enough to reach 100mbit.

Switching to a denser and more efficient modulation would solve it
right away.  It could be done by strapping a driver onto a GNURadio
USRP, for example, but the challenge is getting the cost down to RONJA
levels.