Abstract:
A system and method for increasing bandwidth efficiency and data transmission performance of radio frequency wireless, optical wireless and fiber-optic digital communication links without requiring an increase in signal power. The system utilizes bandwidth efficient space-time coding to correct transmission errors and bandwidth efficient space-time modulation to dramatically increase data throughput without requiring additional signal bandwidth or power. Radio frequency wireless, optical wireless WDM and fiber-optic applications are achieved by utilizing space-time encoders, radio frequency sources, bandwidth efficient space-time modulators and power amplifiers combined with transmission devices such as one or more antennas, multifeed antennas, multimode antennas or for transmission by a suitable cable. At the receiver, the method is reversed.

Description:
This Application is a Continuation-In-Part of application Ser. No. 10/029,599 filed Dec. 20, 2001 and also claims priority of Provisional Application Ser. No. 60/400,578 filed Aug. 1, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a system and method for increasing the bandwidth efficiency and data transmission performance of radio frequency wireless, optical wireless and fiber-optics digital communication link without requiring an increase in the signal power. 
   2. Background Information 
   With the growth of internet, broadband connectivity has been considered the future of the global telecommunication industry. The increasing demands in running near real time applications in the web have exhausted most of licensed and unlicensed spectral bands previously allocated for commercial wireless, metro and long-hauled DWDM fiber-optics systems. The most cost effective solution of this problem is to dramatically improve the efficiency of transmitting information over the present spectrum allocation without requiring major changes in the existing telecommunication infrastructure. 
   The communication efficiency associated with transmitting information is known to be dependent upon the signal design, error correction code as well as the characteristics of the transmission medium. While the theories of high-speed digital communications in the time domain are known, there has been little progress to utilize additional dimensions in the spatial domain as information carriers. There was some advancement in recent years to exploit the spatial capacity by inserting additional antennas as in an antenna array. Each antenna would carry multiple temporal frequency channels. 
   One example is in the U.S. Pat. No. 614,471 of Raleigh et al that discloses an algorithm to process temporal frequency channels from multiple antennas in achieving orthogonal signal properties. This access technique is commonly known as orthogonal frequency division multiplexing (OFDM). Another example is in U.S. Pat. No. 6,285,720B1 of Martone that reveals the advantages in using an antenna array to sample a wavefield distorted by a wireless propagation channel. Details of array processing is disclosed in U.S. Pat. No. 6,317,411B1 of Whinnett et al, while Huang et al presents their ideas in using code division multiple access (CDMA) in wireless antenna array processing, in U.S. Pat. No. 6,301,293B1. These types of space-time system design gain some advantages in realizing temporal frequency diversity and some spatial path diversity through different antennas. However, they fail to exploit multiple spatial modes and they fall short of actually implementing spatial modulation in the transverse electric field as disclose in this present invention. 
   It is one object of the present invention to provide a system and method for increasing the spectral efficiency of a wireless and optical communication channel. 
   It is another object of the present invention to minimize the transmission errors by performing multiple iterative decoding on the received data. 
   Yet another object of the present invention is to increase code rate by transmitting redundant data through the spatial channels. 
   Still another object of the present invention is to mitigate errors induced by fading and scintillation using the interleaver that scrambles the combined spatial and temporal sequence. 
   Still another object of the present invention is to increase the coding gain by transmitting data sequence through the orthogonal polarization channels in a single mode system. 
   Still another object of the present invention is to increase the coding gain by transmitting data sequence through the orthogonal spatial channels in a multi-mode system. 
   Still another object of the present invention is to expand transmission capacity via spatial dimensions. 
   Still another object of the present invention is to increase throughput of a wireless radio frequency transmission system by using multiple and multifeed antennas. 
   Still another object of the present invention is to increase throughput of a wireless optical transmission system by using multiple and multimode antennas. 
   Still another object of the present invention is to increase throughput of a fiber optical transmission system by using multiple and multimode fibers. 
   Still another object of the present invention is to increase throughput of a wireless optical and fiber optical transmission system by using multiple wavelengths. 
   Still another object of the present invention is to increase spectral efficiency by varying the polarization states of the transmitting fields. 
   Still another object of the present invention is digital modulation of polarization states of transmitting fields by polarization phase shift keying. 
   Still another object of the present invention is digital modulation of polarization states of transmitting fields by polarization frequency shift keying. 
   Still another object of the present invention is digital modulation of polarization states of transmitting fields by polarization amplitude shift keying. 
   Still another object of the present invention is high level digital modulation of M polarization states of transmitting fields by M-ary polarization phase and amplitude modulation. 
   Still another object of the present invention is high level digital modulation of M polarization states of transmitting fields that constitute a spherical constellation. 
   Still another object of the present invention is analog modulation of polarization states of transmitting fields by polarization phase modulation. 
   Still another object of the present invention is analog modulation of polarization states of transmitting fields by polarization frequency modulation. 
   Still another object of the present invention is analog modulation of polarization states of transmitting fields by polarization amplitude modulation. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The purpose of the present invention is to apply space-time modulation to increase spectral efficiency for data carrying capacity and to apply space-time coding to improve signal power sensitivity while achieving near error-free transmission performance at the physical layer. 
   The basis of the present invention disclosed herein is a direct application of the space-time modulation theory to wireless communications, free-space optical communications and fiber-optics communications. The fundamental theory related to the present invention is described by Victor Lo in “ On A Statistical Space - Time Modulation Theory,”  Proc. IEEE P.R. Conference on Communications, Computers and Signal Processing, pp. 584-589, Victoria, B.C., Canada, June 1989. 
   Space-time modulation provides capacity expansion by utilizing a three-dimensional spatial field. Spatial modulation can be expressed in the form of changes in vector directions of spatial carriers, Ex, Ey as well as the specific spatial location where the electric field illuminated. The relationship of the x y components and its propagation direction z forms the basic functions for data transmission. When the spatial dimension is not being used as in the case of a linearly polarized signal, all data loading is limited in time along the propagation axis pointing at only one receiver location. Assuming a space-time separable channel, the temporal information carrier on the propagation axis becomes independent of the transverse plane where the relative phase position (state of polarization) can be modulated. Multiple spatial modes can also be generated from a single antenna aperture to transmit independently and concurrently to multitude of receiver locations. By utilizing both spatial and temporal modulation, total system throughput can be substantially increased. 
   Using the Poincare sphere to represent states of polarization in the Stokes&#39; space, an asymmetric field strength between x and y will project a circular trajectory on the Poincare sphere with the biggest radius when a x  is equal to a y . The relative phase difference between x and y will determine the classification of linear, elliptical and circular polarization. The scaling of the field strength will decide the degree of polarization within each classification. In the context of the Poincare space, phase shift keying will appear as equally spaced points on a circle of the Poincare sphere. The exact plane of the circle is set by amplitude a x  and a y . Similarly, frequency shift keying manifests as a rotating circle on the Poincare sphere. The speed of rotation is twice the phase deviation between Ex and Ey. As long as there is enough frequency separation between each symbol, there should not be any difficulty in detecting the frequency modulated symbols. Hardware implementation of a polarization modulator has been described by Sergio Benedetto in “ Multilevel Polarization Modulation Using A Specifically Designed LiNbO,”  IEEE Photonic Tech. Lett, August 1994, pp. 949-951. Details of a polarization receiver suitable for this invention are discussed in “ Multilevel Polarization Shift Keying: Optimum Receiver Structure and Performance Evaluation,”  IEEE Trans. On Comm., March 1994, and demodulation tracking loop in “ Polarization Recovery In Optical Polarization Shift - Keying Systems”  IEEE Trans. On Comm., vol. 45, no. 10, October 1997. 
   In general, space-time modulated signal vectors occupy a complex multidimensional signal space. Signal design is simplified for space-time separable signal sets where temporal and spatial signal constellations can be considered separately. Temporal signal constellations can be presented in the inphase and quadrature plane. Their modulation and demodulation follows the classical inphase and quadrature processing of phase and amplitude. More detailed description can be found in “ Performance of combined amplitude and phase modulated communications systems”  by John Hancock and Robert Lucky in IRE Trans Comms, vol. CS-8, pp. 232-237, December 1960. For spatial modulation, by considering constellation points on the three-dimensional spherical surface of the Poincare sphere, the geometric shape of the constellation becomes a polygon. Each signal vector is generated by an explicit ratio of amplitude and phase between the two transverse plane electric field components. If signal constellation is included outside the Poincare&#39;s sphere, the coverage of the polarized signal set is effectively extended to include all partially polarized and non-polarized signal. Such signal set can be created by concentric spherical surfaces with equal angular distance among signal points for the same degree of polarization. The signal constellation can be further expanded to include semi-geometrical structure like a layered cubic construction with equally spaced signal vectors centered at the un-polarized point. Furthermore, there can also be a layered cylindrical surface with its axis aligned with S 1 . Thus, the signal vector is comprised of points on concentric cylinders with each cylinder specified by fixed amplitude ratio. 
   For a multi-mode antenna system, each mode can be independently space-time modulated, and thus carry separate polarization modulated and temporal modulated messages. For a multimode wireless and optical system, the capacity is limited by the total number of independent modes supportable by the channel. Also, the complexity of the receiver will increase quickly because each mode will have to be independently detected and demodulated. For wireless multimode applications, design of a Meander-Line polarizer for each mode is described by Te-Kao Wu in “ Meander - Line Polarizer For Arbitrary Rotation of Linear Polarization,”  IEEE Microwave and Guided Wave Letters, vol. 4, no. 6, June 1994; while for an optical multimode system, details of a multimode design is described by Gagliardi and Karp, “Optical Communications,” Wiley Interscience, New York, 1976. 
   In addition to space-time modulation, the bandwidth efficiency can be improved by applying advanced waveforms, approaching the theoretical limit set forth by the Nyquist Theorem. Further enhancement is achieved by lowering the probability in making symbol errors during transmission (bit error rate) via forward error correction code. The classic turbo coding scheme utilizes multiple temporal independent channels for data transmission to achieve the amount of redundancy required for reliable data transport. Coding for single mode polarization modulated system: Since there are independent orthogonal polarization channels in the transverse plane for each spatial mode, it is ideal for the transmission of redundant data. Due to the inherent spatial diversity in the orthogonal spatial channels, a space-time coded system can be implemented by sending permuted data sequence via multiple paths. With the additional spatial channels, transmitting redundant data will incur no penalty in temporal code rate. The spatial code rate will be increased at least by a factor of two depending on the number of spatial channels available to carry redundant data. Data sequence can be punctured to further increase the code rate. To optimize the coding gain, a multi-dimensional space-time interleaver is used to spread the burst errors evenly over a data frame. The space-time interleaver is also effective in mitigating error sequence induced by space-time dispersive channels. 
   A different component code can be assigned to each channel. Design of component code can be feed-forward convolutional code, product code, block code or combinations of them. The decoding scheme consist of metrics computation along each possible decoding path in the forward as well as in the backward direction. The decoding path corresponding to the maximum likelihood metric will be chosen. Possible decoding algorithm includes soft-input and soft-output (SISO) or the soft-output Viterbi (SOVA). Design for the encoder and decoder for a parallel code structure is described by Claude Berrou et al, “ Near Shannon Limit Error - Correcting Coding and Decoding: Turbo-Codes”,  Proc. ICC&#39;93, Geneve, May 1993, pp. 1064-1070. For a serial code structure, it is shown by Daruish Divsalar et al in “On The Design of Turbo Codes,” TDA Progress Report 42-123, November 1995, pp. 99-121. To further enhance the bandwidth efficiency, adjacent transmission symbols can be constrained during encoding process to follow a minimum phase transition profile. This technique is commonly known as trellis coding method. Detailed description of this method can be found in “ Channel Coding With Multilevel Phase Signals ” by Ungerboeck in IEEE Trans. Info. Theory, vol.IT-28, 1982, pp. 55-67 incorporated herein by reference. 
   For a multi-mode link, the additional dimensions provide even more options in the design of space-time codes. Now, each spatial mode becomes an independent spatial channel available to either carry a new stream of coded data or a redundant stream of interleaved coded data from another channel. These multiple temporal and spatial channels enable repeated looks of the same set of data. The added spatial and temporal diversity results in a dramatic increase of the link margin. This is an effective way to equalize the degradations due to fading and scintillation. 
   One application of these space-time modulation and coding techniques disclosed herein is for commercial fixed and mobile wireless services, where scarce spectral resources and increased radio frequency interference is driving the modem design towards more efficient modulation and coding methods. A single-feed antenna transmitting via a single spatial mode can be easily expanded to a multi-channel architecture using a multi-feed antenna with each feed transmitting an independent spatial mode or channel. Further substantial improvement is possible by deploying multiple antennas with each antenna carrying multiple feeds. 
   Another application is free space optical communications with direct modulation. The space-time coder encodes the input data into a temporal and a spatial data stream. The temporal data is applied directly to the laser, while the spatial data modulates the states of polarization of the optical signal from the laser via the optical space-time modulator. The optical signal is amplified and transmitted through the optical antenna. With proper antenna pointing, the receiver optical antenna field of view and the transmit antenna beamwidth achieves a near line-of-sight geometry. At the receiver, the optical antenna collects the signal. This is followed by spatial demodulation of the states of polarization and temporal demodulation via direct optical detection. The demodulated data stream is next amplified, the space-time data sequence demultiplexed, inversely permutated and finally decoded to recover the transmitted data. 
   Other application in free space optical communications include indirect modulation with homodyne or heterodyne demodulation, where the temporal data modulates the optical output of the laser at the space-time modulator rather than a direct modulation at the input to the laser. At the receiver, a local laser is used for homodyne or heterodyne demodulation to remove the optical carrier before photo-detection of the temporal data as in the case of direct detection. 
   Yet another application of the invention is to extend the single mode free space optical communications link to multimode communication system by connecting multiple modulators in parallel to a single multiplexed space-time coder, which substantially increased spatial diversity via interleaving data symbols among multiple spatial modes. The output of this array of modulators are amplified and then merge into a two dimensional grid on the image plane. The combined optical signal is transmitted through the optical antenna. At the receiver, the combined optical signal is reverted back to individual spatial signals, which are then space-time demodulated and collectively space-time decoded. 
   There is yet another variation of the present invention as applied to free space optical communications. Multiple optical antennas can be used in addition to multimode per antenna. Single antenna processing is now expanded to parallel processing of multiple antennas as multiplexed from the space-time coder and demultiplexed to the space-time decoder. This design expands both capacity (channels) and throughput (data rates) by orders of magnitude above prior art. 
   Another key area of application is in guided optical communications where waveguides like fiber can be used for routing data of Metro and Long haul optical networks. The system setup is similar to free space optical link except that optical antennas for both the transmitter and receiver are no longer needed. 
   Still another application is to increase the number of wavelength channels by adding wavelength division multiplexing (WDM) to the multimode, multi-antennas free-space optical communication links. 
   Still another application is to increase the number of wavelength channels by using wavelength division multiplexing (WDM) in the multimode, multi-fiber guided optical communication links. 
   For multimode application, couplers become the enabler for launching and for receiving both single-mode as well as the combined multimode optical signal through the fiber optical cable. 
   The free space multiple antennas optical link now becomes a multiple optical fiber link, where each individual fiber can simultaneously carrying multiple spatial modes. The front-end encoding, modulation, and the back-end demodulation, decoding signal processing for the fiber optical link are similar to the free space optical link. 
   The above and other objects, advantages, and novel features of the invention will be more fully understood from the following detailed description and the accompanying drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a schematic block diagram of a prior art radio frequency wireless system applying typically phase modulation on a convolutional coded data stream with a single antenna. 
       FIG. 1B  is a schematic block diagram of one embodiment of a single-feed antenna wireless system operating at radio frequency for increasing channel capacity and throughput of wireless communication networks using both bandwidth efficient space-time coder and modulator according to the invention. 
       FIG. 1C  is a schematic block diagram of another embodiment of a wired system at radio frequency for increasing channel capacity and throughput of a wired radio frequency communication networks according to the invention. 
       FIG. 1D  is a schematic block diagram illustrating a multi-feed wireless communication link as an extension of the single-feed design with each feed connected to separate modulators with multiplexed data input from the space-time coder. 
       FIG. 1E  is a schematic block diagram of a variation of the embodiment of  FIG. 1D  that expands the data capacity and throughputs by using antenna array with each antenna carrying multiple feeds. 
       FIG. 2A  is a schematic block diagram of prior art implementation of an unguided optical link with intensity modulation of a data stream usually coded with convolutional or Reed-Solomon parity bits where the receiver performs photo-detection and decoding of the received data stream. 
       FIG. 2B  is a schematic block diagram of an embodiment comprised of a free space optical link with direct modulation and detection for increasing channel capacity and throughput of a free space or an underwater optical communication networks. 
       FIG. 2C  is a schematic block diagram of a variation of the embodiment illustrated in  FIG. 2B  of a free space optical system utilizing indirect modulation and detection. 
       FIG. 2D  is a schematic block diagram of another embodiment comprised of a free space optical link with multimode direct modulation and detection for increasing channel capacity and throughput of a free space or an underwater optical communication networks. 
       FIG. 2E  is a schematic block diagram of a variation of the embodiment illustrated in  FIG. 2D  comprised of a free space optical system utilizing multimode indirect modulation and detection. 
       FIG. 2F  is a schematic block diagram of another embodiment of a free space optical link with multiple antennas, multimode direct modulation and detection for increasing channel capacity and throughput of a free space or an underwater optical communication networks. 
       FIG. 2G  is a schematic block diagram with a variation of the embodiment illustrated in  FIG. 2F  of a free space optical system utilizing multiple antennas, multimode indirect modulation and detection. 
       FIG. 2H  is a schematic block diagram of an embodiment of a free space optical link with direct modulation and detection for increasing channel capacity and throughput of a free space or an underwater optical WDM communication networks. 
       FIG. 2I  is a schematic block diagram with a variation of the embodiment illustrated in  FIG. 2H  of a free space optical WDM system utilizing indirect modulation and detection. 
       FIG. 2J  is a schematic block diagram of another embodiment of a free space optical link with multimode direct modulation and detection for increasing channel capacity and throughput of a free space or an underwater optical WDM communication networks. 
       FIG. 2K  is a schematic block diagram of a variation of the embodiment illustrated in  FIG. 2J  of a free space optical WDM system utilizing multimode indirect modulation and detection. 
       FIG. 2L  is a schematic block diagram of another embodiment of a free space optical link with multiple antennas, multimode direct modulation and detection for increasing channel capacity and throughput of a free space or an underwater optical WDM communication networks. 
       FIG. 2M  is a schematic block diagram with a variation of the embodiment illustrated in  FIG. 2L  of a free space optical WDM system utilizing multiple antennas, multimode indirect modulation and detection. 
       FIG. 3A  is a schematic block diagram of the prior art guided optical system using intensity modulation and photo-detection. 
       FIG. 3B  is a schematic block diagram of yet another embodiment of this invention in which a guided optical system is shown using optical fiber transmission cable with direct modulation and detection. 
       FIG. 3C  is a schematic block diagram of a variation of the embodiment illustrated in  FIG. 3B  of a fiber-optical system utilizing indirect modulation and detection. 
       FIG. 3D  is a schematic block diagram of another embodiment of this invention in which a guided optical system is shown using optical fiber transmission cable with multimode direct modulation and detection. 
       FIG. 3E  is a schematic block diagram of a variation of the embodiment illustrated in  FIG. 3D  of a fiber-optical system utilizing multimode indirect modulation and detection. 
       FIG. 3F  is a schematic block diagram of another embodiment of this invention in which a guided optical system is shown using optical fiber transmission cable with multiple fibers, multimode direct modulation and detection. 
       FIG. 3G  is a schematic block diagram showing a variation of the embodiment illustrated in  FIG. 3F  of a fiber-optical system utilizing multiple fibers, multimode indirect modulation and detection. 
       FIG. 3H  is a schematic block diagram of yet another embodiment of this invention in which a guided optical WDM system is shown using optical fiber transmission cable with direct modulation and detection. 
       FIG. 3I  is a schematic block diagram showing a variation of the embodiment illustrated in  FIG. 3H  of a fiber-optical WDM system utilizing indirect modulation and detection. 
       FIG. 3J  is a schematic block diagram of another embodiment of this invention in which a guided optical WDM system is shown using optical fiber transmission cable with multimode direct modulation and detection. 
       FIG. 3K  is a schematic block diagram showing a variation of the embodiment illustrated in  FIG. 3J  of a fiber-optical WDM system utilizing multimode indirect modulation and detection. 
       FIG. 3L  is a schematic block diagram of another embodiment of this invention in which a guided optical WDM system is shown using optical fiber transmission cable with multiple fibers, multimode direct modulation and detection. 
       FIG. 3M  is a schematic block diagram showing a variation of the embodiment illustrated in  FIG. 3L  of a fiber-optical WDM system utilizing multiple fibers, multimode indirect modulation and detection. 
       FIG. 4A  is a schematic diagram illustrating the digital symbols generated by polarization phase shift keying. 
       FIG. 4B  is a schematic diagram illustrating the digital symbols generated by polarization frequency shift keying. 
       FIG. 4C  is a schematic diagram illustrating the digital symbols generated by polarization phase and amplitude shift keying. 
       FIG. 4D  is a schematic diagram illustrating the digital symbols generated by polarization concentric spherical amplitude shift keying. 
       FIG. 5A  is a schematic block diagram illustrating the detail processing of single mode bandwidth efficient space-time encoder. 
       FIG. 5B  is a schematic block diagram illustrating the detail processing of multimode bandwidth efficient space-time encoder. 
       FIG. 5C  is a schematic block diagram illustrating the detail processing of multiple antennas multimode bandwidth efficient encoder. 
       FIG. 6A  is a schematic block diagram illustrating the detail processing of single mode bandwidth efficient space-time decoder. 
       FIG. 6B  is a schematic block diagram illustrating the detail processing of multimode bandwidth efficient space-time decoder. 
       FIG. 6C  is a schematic block diagram illustrating the detail processing of multiple antennas multimode bandwidth efficient decoder. 
       FIG. 7A  is a schematic block diagram illustrating the detail processing of bandwidth efficient space-time wireless modulator. 
       FIG. 7B  is a schematic block diagram illustrating the detail processing of the bandwidth efficient space-time optical modulator. 
       FIG. 8A  is a schematic block diagram illustrating the detail processing of bandwidth efficient space-time wireless demodulator. 
       FIG. 8B  is a schematic block diagram illustrating the detail processing of the bandwidth efficient space-time optical demodulator. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In accordance with the invention disclosed herein, channel capacity and data throughput of wireless, free-space optical, and fiber-optical communication links can be dramatically increased depending on the order of space-time modulation, transmission waveform, space-time error correction code, the number of spatial and temporal modes, as well as the size of the transmit and receive antenna array. For a typical wireless system generating a temporally coded and temporally modulated signal followed by a single-feed antenna transmitting to a single-feed antenna receiving system, the wireless link capacity, throughput and bit error rate performance is limited by the efficiency of the temporal modulation and effectiveness of the error correction code used. The present invention significantly increases the system throughput and performance of prior art by encoding data with a space-time error correction code, followed by space-time modulation using a bandwidth efficient waveform before transmission via a plurality of spatial modes per antenna and a plurality of antennas. 
   The prior art implementation of a wireless communication system is illustrated in FIG.  1 A. It consists of a RF carrier generated from a radio frequency source  18 , modulated by convolutional encoded data from  10  at the RF modulator  12 . The signal is amplified and transmitted through a wireless antenna. At the receiving antenna  20 , the transmitted signal is amplified  22  and demodulated  24  before Viterbi decoding  26 . 
   One embodiment of the invention for a wireless communications link with a single feed antenna is illustrated in FIG.  1 B. It consists of an RF carrier source from RF oscillator  18 , space-time modulated by a spatial and temporal data stream from space-time bandwidth efficient coder  10  at bandwidth efficient space-time modulator  12 . The signal is amplified by power amplifier  14  before emission from wireless antenna  16 . At the receiver, the RF signal is collected at wireless antenna  20 , amplified by low noise amplifier  22  to boost the level, followed by demodulation by space-time demodulator  24 . Finally, the demodulated spatial and temporal data streams are decoded by space-time decoder  26 . 
   Bandwidth efficient space-time coder  10  performs the encoding function of the raw data into a coded sequence. As illustrated in  FIG. 5A , the encoding tasks can be partitioned into space-time data permutation  30 , multiple component trellis encoding of space-time data by a plurality of space-time data encodes  32   1  to  32   N , followed by a space-time encoding data processor  34  that multiplexes the various component codes into a spatial and a temporal data streams for space-time modulation. 
   At the receiver, space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. The decoding operation is shown in FIG.  6 A. Space-time decoding data processor  40  de-multiplexes the space-time symbols from the demodulator into various coded components. Under the iterative decoding feedback controller, various coded components are then individually trellis decoded by a plurality of forward-backward path metric processors  44   1  to  44   N  according to the maximum a posteriori probability (MAP) rule. An inverse mapping of data position is then carried out at space-time inverse data permuter  46  and majority logic decoder  48  to recover the raw data. For achieving superb coding gain, a feedback type of iterative decoding process via space-time data permuter  30  is used. 
   Bandwidth efficient space-time modulator  12  performs mapping of space-time data symbols to a multi-dimensional of space-time signal space. The temporal signal constellation follows the two dimensional inphase and quadrature plane representation of amplitude and phase. The spatial modulation is represented by one of the constellation of distinct polarization states in the Poincare sphere as shown in FIG.  4 A through FIG.  4 D.  FIG. 4A  constellation corresponds to polarization phase shift keying in the plane of Stokes parameters S 2  and S 3 .  FIG. 4B  shows a constellation of polarization frequency shift keying in multiple planes defined by S 1 .  FIG. 4C  illustrates the constellation scheme of spherical amplitude shift keying where all three Stokes parameters S 1 , S 2  and S 3  are required to specify each polarization state. By expanding  FIG. 4C  constellation to include inner spheres,  FIG. 4D  shows the layout of concentric spherical amplitude shift keying. 
   The implementation of bandwidth efficient space-time modulator  12  is shown in block diagram FIG.  7 A. Bandwidth efficient space-time modulator  12  is comprised of an RF input port connected to radio frequency splitter  50  that produces two outputs. These outputs are polarized by radio frequency polarizer  52  to form orthogonal polarization states. Space-time modulators  56  and directional coupler  54  provide a symmetric mapping operation in shifting phase, amplitude and frequency in the inphase and quadrature temporal signal space and in the Stokes space of the RF signal under the control of space-time modulation processor  58  based on the input spatial and temporal data stream. The two orthogonal polarization outputs of space-time modulator  56  are recombined by RF combiner  50  after reversing polarization rotation by RF polarizer  52 . 
   Bandwidth efficient space-time demodulator  24  is illustrated in FIG.  8 A. It performs functions of spatial and temporal demodulation. Temporal demodulator  72  performs inphase and quadrature demodulation of the temporal signal. Spatial demodulation consists of Stokes vector estimator  60 , followed by a control loop comprised of track and hold circuit  62 , analog to digital converter  64 , filter  66 , digital to analog converter  68  and decision logic block  70 . Stokes vector estimator  60  derives the polarization states of the received radio frequency signal while the tracking loop maintains symbol synchronization throughout the demodulation operation. 
   Another embodiment of the invention for a single-cabled space-time communications link is illustrated in FIG.  1 C. It consists of a RF carrier from source  18 , space-time modulated by a spatial and temporal data stream from a space-time bandwidth efficient coder  10  at bandwidth efficient space-time modulator  12 . The signal is power amplified  14  before transmission through the cable. At the receiving end of the cable, the RF signal is amplified by low noise amplifier  22  followed by space-time demodulation by demodulator  24 . Finally, the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   Another embodiment of the invention for a wireless communications link using a multi-feed antenna is illustrated in FIG.  1 D. It consists of a plurality of RF carriers from RF oscillator sources  18   1  through  18   M , space-time modulation by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . The plurality of signals are amplified by power amplifiers  14   1  to  14   M , before emission from antenna  16 . At the receiver, the RF signal is collected at antenna  20  and then divided into a plurality of multi-feed signals. These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level, followed by bandwidth efficient space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   While the implementation of the bandwidth efficient space-time modulator and demodulator remains the same as in earlier embodiments. The multi-feed antenna requires multiple space-time data streams provided by the multimode bandwidth efficient space-time coder shown in FIG.  5 B. For multimode operation, the space-time encoding data processor can support M channels of space-time data streams. 
   At the receiver, bandwidth efficient space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. The multimode decoding operation is shown in FIG.  6 B. Space-time decoding data processor  40  de-multiplexes M channels of the space-time symbols from the demodulator into various coded components. Under the iterative decoding feedback controller  42 , various coded components are then individually trellis decoded by a plurality of forward-backward path metric processors  44   1  to  44   N  according to the maximum a posteriori probability (MAP) rule. An inverse mapping of data position is then carried out at the space-time inverse data permuter  46  and majority logic decoder  48  to recover the raw data. 
   Another embodiment of the invention for a wireless communications link using a multi-feed multi-antenna is illustrated in FIG.  1 E. It consists of a plurality of RF carrier signal sources from RF oscillators  18   1  through  18   M , space-time modulation by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of the signals are amplified by power amplifiers  14   1  to  14   M , before emission from a plurality of multifeed wireless antennas  16   1  through  16   K  At the receiver, the RF signal is collected at a plurality of multifeed wireless antennas  20   1  through  20   L  Each antenna output is divided into a plurality of multi-feed signals. These signals are amplified by law noise amplifiers  22   1  through  22   M  to boost the level to compensate for path loss, followed by space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   The multi-feed multi-antenna system requires multiple sets of M channel space-time data streams provided by the multimode multi-antenna bandwidth efficient space-time coder shown in FIG.  5 C. For multi-antenna operation, the space-time encoding data processor can support multiple M channels of space-time data streams. 
   At the receiver, bandwidth efficient space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. The multi-antenna multimode decoding operation is shown in FIG.  6 C. Space-time decoding data processor  40  de-multiplexes K sets of M channels space-time symbols from the demodulator into various coded components. Under the iterative decoding feedback controller  42 , various coded components are then individually trellis decoded by a plurality of forward-backward path metric processors  44   1  to  44   N  according to the maximum a posteriori probability (MAP) rule. An inverse mapping of data position is then carried out at the space-time inverse data permuter  46  and majority logic decoder  48  to recover the raw data. 
   The prior art implementation of a wireless optical communication system is illustrated in FIG.  2 A. It consists of optical carrier generated from laser source  18 , modulated by a forward error correction (FEC) coder  10  to produce encoded data. The signal is amplified and transmitted through optical antenna  16 . At low noise receiving antenna  20 , the transmitted signal is amplified by amplifier  22  and detected by photodetector  24  before decoding by FEC decoder  26 . 
   An embodiment of the invention for a direct modulated wireless optical communications link with a single feed antenna is illustrated in FIG.  2 B. It consists of optical carrier signal from laser source  18 , space-time modulated by a spatial and temporal data stream from space-time bandwidth efficient coder  10  at bandwidth efficient space-time modulator  12 . The signal is amplified by power amplifier  14  before emission from optical antenna  16 . At the receiver, the optical signal is collected at antenna  20 , space-time demodulated by demodulator  24  and amplified by low noise amplifier  22  to compensate for losses. Finally, the demodulated spatial and temporal data streams are decoded by space-time decoder  26 . 
   Bandwidth efficient space-time coder  10  performs the encoding function of the raw data into a coded sequence as illustrated in FIG.  5 A and described previously. 
   At the receiver, space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. The decoding operation is shown in FIG.  6 A. Space-time decoding data processor  40  de-multiplexes the space-time symbols from the demodulator into various coded components. Under the iterative decoding feedback controller, various coded components are then individually trellis decoded by a plurality of forward-backward path metric processors  44   1  to  44   N  according to the maximum a posteriori probability (MAP) rule. An inverse mapping of data position is then carried out at the space-time inverse data permuter  46  and the majority logic decoder  48  to recover the raw data. For achieving superb coding gain, a feedback type of iterative decoding process via space-time data permuter  30  is used. 
   Bandwidth efficient space-time modulator  12  performs mapping of space-time data symbols to a multi-dimensional of space-time signal space. The temporal signal constellation follows the two dimensional inphase and quadrature plane representation of amplitude and phase. Spatial modulation is represented by one of the constellation of distinct polarization states in Poincare sphere as shown and described previously with reference to FIGS.  4 A through FIG.  4 D. 
   The implementation of bandwidth efficient space-time modulator  12  is shown in block diagram of FIG.  7 B. Bandwidth efficient space-time modulator  12  is comprised of an optical input port connected to a polarization beam splitter  50  that produces two outputs with orthogonal polarization states. The outputs are rotated by polarization rotator  52 . Space-time modulators  56  and directional coupler  54  provide a symmetric mapping operation in shifting phase, amplitude and frequency in the inphase and quadrature temporal signal space and in the Stokes space of the optical signal under the control of space-time modulation processor  58  based on input spatial and temporal data stream. The two orthogonal polarization outputs of space-time modulator  56  are recombined by polarization beam splitter  50  after reversing rotation back by polarization rotator  52 . 
   Bandwidth efficient space-time demodulator  24  is illustrated and its operation described previously with reference to FIG.  8 B. It performs functions of spatial and temporal demodulation. Temporal demodulator  72  performs inphase and quadrature demodulation of the temporal signal. Spatial demodulation consists of Stokes vector estimator  60 , followed by a control loop comprised of track and hold circuit  62 , analog to digital converter  64 , filter  66 , digital to analog converter  68  and decision logic block  70 . Stokes vector estimator  60  derives the polarization states of received optical signal while the tracking loop maintains symbol synchronization throughout the demodulation operation. 
   Another embodiment of the invention for an indirect modulated wireless optical communications link with a single feed antenna is illustrated in FIG.  2 C. It consists of optical carrier from laser source  18 , space-time modulated by a spatial and temporal data stream from space-time bandwidth efficient coder  10  at the bandwidth efficient space-time modulator  12 . The signal is amplified by power amplifier  14  before emission from optical antenna  16 . At the receiver, the optical signal is collected at antenna  20 , demodulated by space-time demodulator  24  and amplified by amplifier  22 . Finally, the demodulated spatial and temporal data streams are decoded by space-time decoder  26 . 
   Another embodiment of the invention for a direct modulated wireless optical communications link using a multi-mode coupled antenna is illustrated in FIG.  2 D. It consists of a plurality of optical carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of the optical signals are power amplified by power amplifiers  14   1  to  14   M , before emission from optical antenna  16 . At the receiver, the optical signal is collected by antenna  20  and then divided into a plurality of multi-mode signals. These signals are amplified by amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   While the implementation of the optical bandwidth efficient space-time modulator and demodulator remains the same as in earlier embodiments. The multi-mode coupled optical antenna requires multiple space-time data streams provided by the multimode bandwidth efficient space-time coder shown in FIG.  5 B. For multimode operation, space-time encoding data processor can support M channels of space-time data streams. 
   At the receiver, bandwidth efficient space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. Multimode decoding operation is shown in FIG.  6 B. Space-time decoding data processor  40  de-multiplexes M channels of space-time symbols from demodulator into various coded components. Under the iterative decoding feedback controller, various coded components are then individually trellis decoded by a plurality of forward-backward path metric processors  44   1  to  44   N  according to the maximum a posteriori probability (MAP) rule. An inverse mapping of data position is then carried out at the space-time inverse data permuter  46  and majority logic decoder  48  to recover the raw data. 
   Another embodiment of the invention for an indirect modulated wireless optical communications link using a multi-mode coupled antenna is illustrated in FIG.  2 E. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of the optical signals are amplified by power amplifiers  14   1  to  14   M , before emission from optical antenna  16 . At the receiver, the optical signal is collected by antenna  20  and then divided into a plurality of multi-mode signals. These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by space-time decoder  26 . 
   Another embodiment of the invention for a direct modulated wireless optical communications link using a multimode coupled multi-antenna is illustrated in FIG.  2 F. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of signals are amplified by power amplifiers  14   1  to  14   M , before emission from a plurality of antennas  16   1  through  16   K . At the receiver, the optical signal is collected by a plurality of antennas  20   1  through  20   L . Each antenna output is divided into a plurality of multimode signals. These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   The multi-mode coupled multi-antenna system requires multiple sets of M channel space-time data streams provided by the multimode multi-antenna bandwidth efficient space-time coder shown in FIG.  5 C and described previously. 
   At the receiver, bandwidth efficient space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. The multi-antenna multimode decoding operation is shown in FIG.  6 C. Space-time decoding data processor  40  de-multiplexes K sets of M channels space-time symbols from the demodulator into various coded components. Under the iterative decoding feedback controller  42 , various coded components are then individually trellis decoded by a plurality of forward-backward path metric processors  44   1  to  44   N  according to the maximum a posteriori probability (MAP) rule. An inverse mapping of data position is then carried out at space-time inverse data permuter  46  and majority logic decoder  48  to recover the raw data. 
   Another embodiment of the invention for an indirect modulated wireless optical communications link using a multimode-coupled multi-antenna is illustrated in FIG.  2 G. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of the signals are amplified by power amplifiers  14   1  to  14   M , before emission from a plurality of antennas  16   1  through  16   K . At the receiver, the optical signal is collected at a plurality of antennas  20   1  through  20   K . Each antenna output is divided into a plurality of multimode signals. These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   One embodiment of the invention for direct modulated wireless optical WDM communications link with a single feed antenna is illustrated in FIG.  2 H. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   N , space-time modulated by a spatial and temporal data stream from space-time bandwidth efficient coders  10   1  to  10   N  at the bandwidth efficient space-time modulator  12   1  through  12   N  The signal is multiplexed by wavelength multiplexer  80  followed by wideband power amplification by power amplifier  14  before emission from optical antenna  16 . At the receiver, the optical signal is collected at antenna  20 , demultiplexed by wavelength demultiplexer  82  before space-time demodulation by demodulators  24   1  through  24   N  and amplified by low noise amplifiers  22   1  through  22   N . Finally, the demodulated spatial and temporal data streams are decoded by the space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for indirect modulated wireless optical WDM communications link with a single feed antenna is illustrated in FIG.  2 I. It consists of optical signal carrier from laser source  18   1  through  18   N , space-time modulated by a spatial and temporal data stream from space-time bandwidth efficient coders  10   1  to  10   N  at bandwidth efficient space-time modulators  12   1  through  12   N  The signal is wideband amplified by power amplifier  14  before emission from optical antenna  16 . At the receiver, the optical signal is collected at the antenna  20 , demultiplexed by wavelength demultiplexer  82  before demodulation by space-time demodulators  24   1  through  24   N  and amplified at  22   1  through  22   N . Finally, the demodulated spatial and temporal data streams are decoded by space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for a direct modulated wireless optical WDM communications link using a multi-mode coupled antenna is illustrated in FIG.  2 J. It consists of a plurality of optical carriers from laser sources  18   1  through  18   M  for M modes, space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coders  10   1  to  10   N  for N wavelengths at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . The multimode multi-wavelengths optical signals are coupled by multimode coupler  84   1  to  84   N , wavelength division multiplexed by multiplexer  80  and wideband amplified by power amplifier  14 , before emission from optical antenna  16 . At the receiver, the optical signals are collected at antenna  20 , wavelength division demultiplexed by demultiplexer  82  and then divided into a plurality of multi-mode signals by multimode decouplers  86   1  to  86   N . These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by a plurality of space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for an indirect modulated wireless optical WDM communications link using a multi-mode coupled antenna is illustrated in FIG.  2 K. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M  for M modes, space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coders  10   1  to  10   N  for N wavelengths at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . The multimode multi-wavelengths optical signals are coupled by multimode couplers  84   1  to  84   N , wavelength division multiplexed by multiplexer  80  and wideband power amplified by amplifier  14 , before emission from optical antenna  16 . At the receiver, the optical signal is collected at antenna  20 , wavelength division demultiplexed by demultiplexer  82  and then divided into a plurality of multi-mode signals by multimode decouplers  86   1  to  86   N . These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by a plurality of space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for a direct modulated wireless optical WDM communications link using multimode coupled multi-antenna is illustrated in FIG.  2 L. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M  for M modes, space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coders  10   1  to  10   N  for N wavelengths at a plurality of bandwidth efficient space-time modulators  121  through  12 M. The multimode multi-wavelengths optical signals are coupled by multimode couplers  84   1  to  84   N , multiplexed by wavelength division multiplexers  80   1  to  80   K  for K antennas and wideband power amplified by amplifiers  14   1  to  14   K , before emission from a plurality of antennas  16   1  through  16   K . At the receiver, the optical signal is collected at a plurality of antennas  20   1  through  20   K , wavelength division demultiplexed by demultiplexers  82   1  to  82   K  and then divided into a plurality of multimode signals by multimode decouplers  86   1  to  86   N  per each antenna respectively. These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by a plurality of space-time decoders  26   1  to  26   N  per antenna. 
   Another embodiment of the invention for an indirect modulated wireless optical WDM communications link using multimode-coupled multi-antenna is illustrated in FIG.  2 M. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coders  10   1  to  10   N  for N wavelengths at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . The multimode multi-wavelengths optical signals are coupled by multimode couplers  84   1  to  84   K , multiplexed by wavelength division multiplexers  80   1  to  80   K  for K antennas and wideband power amplified by amplifiers  14   1  to  14   K , before emission from a plurality of antennas  16   1  through  16   K . At the receiver, the optical signal is collected at a plurality of antennas  20   1  through  20   K  wavelength division demultiplexed demultiplexers  82   1  to  82   K  and then divided into a plurality of multimode signals by multimode decouplers  86   1  to  86   K  per each antenna respectively. These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoders  26 S 1  to  26   N  per antenna. 
   The prior art implementation of a fiber optical communication system is illustrated in FIG.  3 A. It consists of optical signal carrier generated from laser source  18 , modulated by a forward error correction (FEC) coder  10  producing encoded data. The signal is amplified by low noise amplifier  18  and transmitted through optical fiber  28 . At the receiving end of the fiber, the transmitted signal is detected by photodetector  24  and amplified by low noise amplifier  22  before decoding by FEC decoder  26 . 
   One embodiment of the invention for a direct modulated fiber optical communications link is illustrated in FIG.  3 B. It consists of optical carrier from laser source  18 , space-time modulated by a spatial and temporal data stream from space-time bandwidth efficient coder  10  at the bandwidth efficient space-time modulator  12 . The signal is amplified by power amplifier  14  before transmission by optical fiber  28 . At the receiving end of the fiber, the optical signal is amplified by low noise amplifier  22  and space-time demodulated by demodulator  24 . Finally, the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   Bandwidth efficient space-time coder  10  performs the encoding function of raw data into a coded sequence. The encoding tasks illustrated were described previously with reference to FIG.  5 A. 
   At the receiver, space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. The decoding operation is shown in FIG.  6 A and was described previously. 
   Bandwidth efficient space-time modulator  12  performs mapping of space-time data symbols to a multi-dimensional of space-time signal space. Temporal signal constellation follows the two dimensional inphase and quadrature plane representation of amplitude and phase. The spatial modulation is represented one of the constellation of distinct polarization states in Poincare sphere as shown and described previously with reference to FIGS.  4 A through FIG.  4 D. 
   Implementation of bandwidth efficient space-time modulator  12  is shown and described previously with reference to the block diagram of FIG.  7 B. 
   Bandwidth efficient space-time demodulator  24  is illustrated and its operation described previously with reference to FIG.  8 B. 
   Another embodiment of the invention for an indirect modulated fiber optical communications link is illustrated in FIG.  3 C. It consists of optical signal carrier from laser source  18 , space-time modulated by a spatial and temporal data stream from space-time bandwidth efficient coder  10  at the bandwidth efficient space-time modulator  12 . The signal is amplified by power amplifier  14  before transmission by optical fiber  28 . At the receiver, the optical signal is collected from optical fiber  28 , space-time demodulated by demodulator  24  and amplified by low noise amplifier  22 . Finally, the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   Another embodiment of the invention for a direct modulated multimode fiber optical communications link is illustrated in FIG.  3 D. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of the optical signals are amplified by power amplifiers  14   1  to  14   M , before coupling into the optical fiber  28  by fiber optics transmit coupler  16 . At the receiving end, the optical signal is divided into a plurality of multi-mode signals by fiber optics receive decoupler  20 . These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   While the implementation of the optical bandwidth efficient space-time modulator and demodulator remains the same as in earlier embodiments. Multi-mode coupled optical fiber requires multiple space-time data streams provided by multimode bandwidth efficient space-time coder are as shown and described previously with reference to FIG.  5 B. 
   At the receiver, bandwidth efficient space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. Multimode decoding operation is shown FIG.  6 B and was described previously. 
   Another embodiment of the invention for an indirect modulated multimode fiber optical communications link is illustrated in FIG.  3 E. It consists of a plurality of optical carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of optical signals are amplified by power amplifiers  14   1  to  14   M , before coupling into the optical fiber  28  by fiber optics transmit coupler  16 . At the receiving end, the optical signal is divided into a plurality of multi-mode signals by fiber optics receive decoupler  20 . These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   Another embodiment of the invention for a direct modulated multimode fiber optical communications link is illustrated in FIG.  3 F. It consists of a plurality of optical carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of signals are amplified by power amplifiers  14   1  to  14   M , before coupling into a plurality of optical fibers  28   1  through  28   K  by fiber optics transmit couplers  16   1  through  16   K . At the receiving end of the fiber, the optical signal is divided into a plurality of multimode signals by fiber optics receive decouplers  20   1  through  20   K . These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   The multi-mode coupled multi-fiber system requires multiple sets of M channel space-time data streams provided by multimode multi-antenna bandwidth efficient space-time coder shown in FIG.  5 C and described previously. 
   At the receiver, bandwidth efficient space-time decoder  26  decodes the demodulated space-time symbols to recover the original transmitted data. Multi-antenna multimode decoding operation is shown in FIG.  6 C and was previously described. 
   Another embodiment of the invention for an indirect modulated multimode fiber optical communications link is illustrated in FIG.  3 G. It consists of a plurality of optical carriers from laser sources  18   1  through  18   M , space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coder  10  at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of signals are amplified by power amplifiers  14   1  to  14   M , before coupling into a plurality of optical fibers  28   1  through  28   K  by fiber optics transmit couplers  16   1  through  16   K . At the receiving end of the fiber, the optical signal is divided into a plurality of multimode signals by fiber optics receive decouplers  20   1  through  20   K . These signals are amplified by low noise amplifiers  22   1  through  22   M  to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoder  26 . 
   One embodiment of the invention for a direct modulated fiber optical WDM communications link is illustrated in FIG.  3 H. It consists of optical carrier from a plurality of laser sources  18   1  to  18   N  for N wavelengths, space-time modulated by a spatial and temporal data stream from a plurality of space-time bandwidth efficient coders  10   1  to  10   N  at the plurality of bandwidth efficient space-time modulators  12   1  to  12   N  The signal is wavelength multiplexed by multiplexer  80 , wideband amplified by power amplifier  14  before transmission from optical fiber  28 . At the receiving end of the fiber, the optical signal is wavelength demultiplexed by demultiplexer  82 , amplified by low noise amplifiers  22   1  to  22   N  and space-time demodulated by demodulators  24   1  to  26   N . Finally, the demodulated spatial and temporal data streams are decoded by the space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for an indirect modulated fiber optical WDM communications link is illustrated in FIG.  3 I. It consists of optical signal carrier from a plurality of laser sources  18   1  to  18   N  for N wavelengths, space-time modulated by a spatial and temporal data stream from space-time bandwidth efficient coders  10   1  to  10   N  at the plurality of bandwidth efficient space-time modulators  12   1  to  12   N  The signal is wavelength multiplexed by multiplexer  80 , wideband amplified by power amplifier  14  before transmission from optical fiber  28 . At the receiving end of the fiber, the optical signal is wavelength demultiplexed by demultiplexer  82 , amplified by low noise amplifiers  22   1  to  22   N  and space-time demodulated by demodulators  24   1  to  26   N . Finally, the demodulated spatial and temporal data streams are decoded by the space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for a direct modulated multimode fiber optical WDM communications link is illustrated in FIG.  3 J. It consists of a plurality of optical carriers from laser sources  18   1  through  18   M  for M modes, space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coders  10   1  to  10   N  for N wavelengths at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of optical signals are coupled by multimode coupler  84 , wavelength multiplexed by multiplexer  80 , wideband amplified by power amplifier  14  before entering into optical fiber  28  by fiber optics transmit coupler  16 . At the receiving end, the optical signal is wavelength demultiplexed by demultiplexer  82  and divided into a plurality of multi-mode decoupled signals by multi-mode decoupler  86 . These signals are amplified by low noise amplifiers  22   1  through  22   M  per wavelength to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for an indirect modulated multimode fiber optical WDM communications link is illustrated in FIG.  3 K. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M  for M modes, space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coders  10   1  to  10   N  for N wavelengths at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of optical signals are coupled by multimode coupler  84 , wavelength multiplexed by multiplexer  80 , wideband amplified by power amplifier  14  before coupling into optical fiber  28 . At the receiving end, the optical signal is wavelength demultiplexed by demultiplexer  82 , divided into a plurality of multi-mode decoupled signals  86  by multimode decoupler  82 . These signals are amplified by low noise amplifiers  22   1  through  22   M  per wavelength to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for a direct modulated multimode fiber optical WDM communications link is illustrated in FIG.  3 L. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M  for M modes, space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coders  10   1  to  10   N  for N wavelengths at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of signals are coupled by multimode couplers  84   1  to  84   K , wavelength multiplexed by multiplexers  80   1  to  80   K , wideband amplified by power amplifiers  14   1  to  14   K , before coupling into a plurality of optical fibers  28   1  through  28   K . At the receiving end of the fibers, the optical signal is wavelength demultiplexed by demultiplexers  82   1  to  82   K , divided into a plurality of multimode decoupled signals by multimode decouplers  86   1  to  86   K . These signals are amplified by low noise amplifiers  22   1  through  22   M  per wavelength to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoders  26   1  to  26   N . 
   Another embodiment of the invention for an indirect modulated multimode fiber optical WDM communications link is illustrated in FIG.  3 M. It consists of a plurality of optical signal carriers from laser sources  18   1  through  18   M  for M modes, space-time modulated by a plurality of spatial and temporal data streams from space-time bandwidth efficient coders  10   1  to  10   N  for N wavelengths at a plurality of bandwidth efficient space-time modulators  12   1  through  12   M . A plurality of signals are coupled by multimode couplers  84   1  to  84   K , wavelength multiplexed by multiplexers  80   1  to  80   K , wideband amplified by power amplifiers  14   1  to  14   K , before coupling into a plurality of optical fibers  28   1  through  28   K . At the receiving end of the fibers, the optical signal is wavelength demultiplexed by demultiplexers  82   1  to  82   K , divided into a plurality of multimode decoupled signals by multimode decouplers  86   1  to  86   K . These signals are amplified by low noise amplifiers  22   1  through  22   M  per wavelength to boost the level after space-time demodulation by demodulators  24   1  to  24   M . Finally, a plurality of the demodulated spatial and temporal data streams are decoded by the space-time decoders  26   1  to  26   N . 
   This invention is not to be limited by the embodiment shown in the drawings and described in the description which is given by way of example and not of limitation, but only in accordance with the scope of the appended claims.