Fiber optic


2.2.4 Fiber optics

Pulses of light sent down ultra-thin (as thin as a human hair or less), ultra-transparent fiber of glass, with total internal reflection (no loss in light as it bounces off side).
Pulse=1, Absence of light=0.
Electrical signal - to - light pulses - to electrical signal.
1-way system. 2-way comms uses 2 fibers, or 2 frequency bands on same fiber.

  1. Sender - LED (low-spec) or Laser (high-spec) converts electrical signal to light pulses.
  2. Receiver - Photodiode detector generates electrical pulse when light falls on it.



Speeds

Fiber optic theoretical transmission limit 50 T bps.
Current practical limit around 50 G bps for 100 km without amplification - Problem is converting between electrical and optical fast enough.
At receiver, photodiode typically cannot convert faster than around 1 G bps.

Seems like computation speed will hit physical limits before communication speed does.
In future? - Computation is slow. Communication is fast. Redesign all systems to minimise computation, no matter how much bandwidth it wastes.


Comparison of fiber optic and copper