Abstract
Optical communication with high photon-efficiency (many bits/photon) and high spectral
efficiency (SE) (many bits/s-Hz) cannot be achieved unless multiple spatial modes are employed.
For vacuum propagation, it is known that achieving 10 bits/photon and 5 bits/s-Hz requires 189
low-loss spatial modes at the ultimate Holevo limit and 4500 such modes at the Shannon limit for
on–off keying with direct detection. For terrestrial propagation paths, however, atmospheric
turbulence corrupts multiple spatial-mode operation. This paper derives power-transmissivity
bounds and average intermodal crosstalks for the turbulent channel that depend solely on the
mutual coherence function of the atmospheric Green’s function. These statistics are then evaluated
for
$\sim$
200 spatial-mode systems whose transmitters use either focused-beam,
Hermite–Gaussian (HG), or Laguerre–Gaussian (LG) modes and whose receivers either do or do not
employ adaptive optics. It is shown that: (1) adaptive optics are not necessary for achieving both
high photon information efficiency (PIE) and high SE; (2) systems employing HG or LG modes achieve
the same capacities through turbulence; and (3) the orbital angular momentum carried by LG modes
does not provide turbulence immunity. In the companion paper [N. Chandrasekaran, J. H. Shapiro,
and L. Wang, “Photon Information Efficient Communication Through Atmospheric Turbulence—Part II:
Bounds on Ergodic Classical and Private Capacities,” J. Lightw. Technol., vol. 32, no. 6, pp.
1088–1097, Mar. 2014], the transmissivity bounds are used to quantify the turbulence-induced loss
in PIE versus SE performance for these mode sets.
© 2013 IEEE
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription