Securing Fiber Using Light Polarization

screenbert writes: "A new and novel way of communicating over fiber optics is being developed by physicists supported by the Office of Naval Research. Rather than using the amplitude and frequency of electromagnetic waves, they're using the polarization of the wave to carry the signal. Such a method offers a novel and elegant method of secure communication over fiber optic lines. This press release has more information. Of course I always thought that fiber was always pretty secure anyway since it's a lot harder to tap than copper."

Comments

Phase Modulation Anyone?

[Genady]

Aren't there any EE's in die Hause? This is nothing more than Phase Modulation for Fiber. You really can't use Frequency Modulation to transmit info down a fiber (Though maybe you could if you think about it with sensitive enough recievers would only need like 2 Hz/Channel for Digital FM.) You usually use Amplitude Modulation (in this case on/off), so why not Phase Modulation?

My question is this, could you increase the data throughput by encoding one signal with AM and another signal with PM? Have one frequency carrying two channels? You'd take a hit on the PM channel since you don't have a constant carrier, but still it'd be cool.