A. Parameters and Notation

The following is a list of parameters and notation used in this paper.

Laser and Modulator parameters
$M$	256, 64, 2	PPM order
$T_s$	$3.125 \times 10^{-8}$	Width of the PPM slot required by laser, in seconds
$T_d$	$4.32 \times 10^{-4}$	Dead time between PPM symbols required by laser, in seconds
$\alpha_{er}$	$10^6$	Modulation extinction ratio
Received light
$\bar n_s$	100	Average number of signal photons incident on the photodetector, per pulse
$\bar n_b$	0.001 - 10,000	Average number of background photons incident on the photodetector, per slot
APD detector parameters
$\eta$	38%	Quantum efficiency
$k_{\mbox{\small \em eff}}$	0.007	Ionization ratio
$T$	300	Noise temperature, in Kelvin
$G$	50-200	Gain
$R$	179700	Load resistance implied by transimpedance model, $5.75\times 10^{12} \times T_s$, in Ohms
$B$	$1\over 2T_s$	Noise equivalent one-sided bandwidth, in Hz.
$I_b$	$4\times 10^{-14}$	Bulk leakage current, in Amperes
$I_s$	$2\times 10^{-9}$	Surface leakage current, in Amperes
Constants
$\kappa$	$1.38\times 10^{-23}$	Boltzmann's constant, in Joules/Kelvin
$e_-$	$1.6\times 10^{-19}$	Electron charge, in Coulombs
Error probabilities
$p$		Probability of correct uncoded PPM detection
$q$		Probability uncoded PPM symbol $i$ is detected as symbol $j$, $j \ne i$.