Spatial domain based multi dimensional coded modulation for multi Tb per second serial optical transport networks
View Patent ↗An optical transport network based on multimode/multicore fibers includes a mode-multiplexer to multiplex independent data streams from one or more transmitters; a multimode erbium-doped fiber amplifier (MM EDFA) to compensate for MMF loss; a multimode optical add-drop multiplexer (MM OADM) to add and/or drop multimode channels in multimode networks; a multimode optical cross-connect; and a mode-demultiplexer to separate various mode streams to one or more receivers.
1. An optical transport network, comprising:
a. a mode multiplexer to combine inputs from one or more transmitters;
b. a multimode erbium-doped fiber amplifier (MMEDFA) to compensate for multimode fiber loss;
c. a multimode optical add-drop multiplexer (MMOADM) to add and/or drop multimode signals;
d. a multimode optical cross-connect; and
e. a mode demultiplexer to separate the mode-multiplexed streams and provide data to one or more receivers
f. code to determine Laguerre-Gauss (LG) and vortex beams with a field distribution of an LG beam traveling along the z-axis in cylindrical coordinates (r,φ,z) (where r denotes radial distance from propagation axis, φ denotes azimuthal angle and z denotes propagation distance).
2. The network of claim 1 , comprising a spatial-domain-based N-dimensional modulator.
3. The network of claim 2 , comprising one electro-optical modulator (EO MOD) per coordinate coupled to a mode-multiplexer.
4. The network of claim 3 , wherein the mode-multiplexer comprises a taper core receiving a plurality of channels.
5. The network of claim 4 , wherein the taper core is coupled to a multimode fiber (MMF).
6. The network of claim 2 , comprising a power splitter coupled to the EO MOD.
7. The network of claim 1 , comprising a passive MM device coupled to an MMF.
8. The network of claim 7 , wherein the passive MM device comprises a mode splitter coupled to a plurality of single mode devices, each of the single mode devices coupled to a mode combiner.
9. The network of claim 1 , wherein the MM EDFA comprises a spatial mode WDM combiner receiving a multimode weak incoming signal and driving a multimode erbium doped fiber.
10. The network of claim 9 , wherein corresponding laser pumps are independently adjusted so that different spatial-modes have the same output power level.
11. The network of claim 1 , wherein K input bits are used as an address in a look-up table in which N-dimensional coordinates are stored and, after selection, used as inputs to the mode-multiplexer by EO MODs.
12. The network of claim 1 , wherein orthogonal demultiplexed modes are used as inputs to a corresponding set of N photodetectors/receivers.
13. The network of claim 1 , comprising a donut-shaped photodetector to simultaneously detect all separate OAM modes of interest.
14. The network of claim 1 , wherein a center frequency of the bands within one band-group are orthogonal to each other to simplify the band detection.
15. The network of claim 1 , comprising a three-layer architecture with a baseband layer, a mode multiplexing layer where several orthogonal OAM modes are used to multiplex corresponding data streams, and a photonic layer.
16. The network of claim 15 , wherein the baseband layer comprises a coded modulation block coupled to DACs and low-pass filters.
17. The network of claim 15 , wherein the photonic layer combines signals from several-frequency locked lasers into a serial optical transport signal.
18. The network of claim 1 , comprising multimode fiber (MMF), multiplexers/demultiplexers, MMF amplifiers, MM optical add-drop multiplexers, MM cross-connects and modes-detector.
19. The network of claim 1 , comprising code to determine.
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where w(z)=w 0 √{square root over (1+(z/z R ) 2 )} (w 0 is the zero-order Gaussian radius at a waist), z R =πw 0 2 /λ is the Rayleigh range (with λ being the wavelength), k=2π/λ is a propagation constant, and L m p (·) is Laguerre polynomial, with p and m representing radial and angular mode numbers.