Multidimensional coded-modulation for high-speed optical transport over few-mode fibers

1. A method for optical data transport, comprising:

formulating a signal constellation using a D-dimensional optimum signal constellation design (OSCD) method, wherein D is an integer, the method comprising including:

determining a D-dimensional optimum source distribution for a given optical channel using an Arimoto-Blahut algorithm;

generating D-dimensional training sequences from the optimum source distribution, with the D-dimensional training sequences being split into D-dimensional clusters of points;

determining new signal constellation points as the center of mass for each D-dimensional cluster of points; and

repeating the formulating steps until convergence or until a predetermined number of iterations has been reached;

encoding one or more streams of input data using one or more low density parity check (LDPC) encoders;

mapping one or more encoded data streams to symbols, wherein a mapper is configured to assign bits of the symbols to one signal constellation and to associate the bits of the symbols with signal constellation points;

generating signal constellation points using a D-dimensional optimum signal constellation design (OSCD) method,

storing coordinates obtained by the D-dimensional OSCD method for a plurality of optical signal to noise ratio (OSNR) values in a look-up-table (LUT);

selecting a point from the LUT using encoded data streams;

inputting the coordinates into a D-dimensional modulator after digital-to-analog conversion (DAC); and

transmitting a modulated signal over a fiber-optic medium of interest.

2. The method as recited in claim 1 , wherein the D-dimensional OSCD is optimum in a minimum mean square error (MMSE) sense for Gaussian-like channels or maximum-likelihood for non-Gaussian channels.

3. The method as recited in claim 1 , wherein the D-dimensional OSCD is applied to an arbitrary number of dimensions.

4. The method as recited in claim 1 , wherein the new signal constellation developed by the D-dimensional OSCD method is applied in a plurality of types of optical channels, including at least one of single-mode fiber (SMF), few-mode fiber (FMF), few-core fiber (FCF), and few-core few-mode fiber (FCFMF).

5. The method as recited in claim 1 , wherein the new signal constellation developed by the D-dimensional OSCD method is applied in at least one of polarization-division multiplexing (PDM) for communication over single-mode fiber (SMF), four-dimensional modulation for communication over SMF, mode multiplexing for communication over few-mode fiber (FMF), and spatial/space division multiplexing for communication over few-core fiber (FCF) and few-core few-mode fiber (FCFMF).

6. The method as recited in claim 1 , wherein D bits are taken from a block-interleaver column-wise and used to select a point from a 2 D -ary signal constellation stored in a look up table (LUT), with the coordinates from the LUT being used as inputs of a D-dimensional modulator.

7. The method as recited in claim 6 , wherein the new signal constellation points are calculated using a D-dimensional modulator by:

S

i

=

C

D

⁢

∑

d

=

1

D

⁢

ϕ

i

,

d

⁢

Φ

d

,

where S i denotes a signal constellation, C D denotes the normalization constant, φ i,d denotes the dth coordinate (d=1, 2, . . . , D) of the ith signal-constellation point (stored in LUT), and the set {Φ 1 , . . . , Φ D } denotes basis functions.