Problem 1a)

Problem 1b)

Note...

Problem 2) Cable cut into two equal sized links, each with loss alpha.

alpha adjusted by hand until Tsys2 approximately equals Tsys

This is the fiber loss per hop...

Km

Problem 3) Two 129.5 Km hops with a Regenerative Repeater in the middle.

The Complementary Error function in MathCAD is being used to generate the
Q Function and is evaluating this particular probability as zero. One approximation that
can be used is the equation below (valid if x > 5)...

The end-to-end bit-error probablity is approximately twice the above qx value.