Accounting
How many dB are left
Given a set of device specs: the effective squeezing at the detector, the floor of this link, and the one term worth fixing.
One master equation
Every other criterion is a corollary of it.
V_out = η·e^(−2r) + (1 − η) + n ; η = 1 − L
The loss term (1−η) and the added noise n are not interchangeable. With a pre-amplifier the equation does not apply.
Floor
V_out ≥ L
The limit as input squeezing goes to infinity: Ae,max = −10·lg L.
Ranking
Derivative
Push one term to its achievable limit and see how many dB come back.
Inverse
Solve
For 9 dB, total loss must fall below 2.88% — a sentence for the requirements document.
Try it
Defaults: 10 dB in, 30% loss.
To account a real link
The detail lives in the files; the page keeps the conclusions.