Increase in reach of unrepeatered fiber transmission

Abstract

The present invention is directed to techniques and systems for extension of unrepeatered submarine fiber links to provide an increase in reach of unrepeatered fiber transmission. Both single channel unrepeatered systems and multiple channel unrepeatered systems can be used. The multiple channel unrepeatered systems can further employ nonlinearity compensation. The present invention is also directed to methods of signal transmission using the unrepeatered systems.

What is claimed is: 
     
         1 . A single-channel unrepeatered system comprising:
 (a) a transmitter;   (b) a transmitting side amplification system;   (c) a transmission line devoid of any inline lumped amplifiers;   (d) a receiving end amplification system; and   (e) a receiver.   
     
     
         2 . The single-channel unrepeatered system of  claim 1  that operates with about 100 Watt (50 dBm) launch power. 
     
     
         3 . The single-channel unrepeatered system of  claim 1  that operates with a reach of from about 750 km to about 790 km. 
     
     
         4 . The single-channel unrepeatered system of  claim 1  that employs advanced higher-order Raman amplification designed to match increased signal launch power. 
     
     
         5 . The single-channel unrepeatered system of  claim 4  that operates with a reach of at least about 1400 km. 
     
     
         6 . The single-channel unrepeatered system of  claim 1  that employs employ an OOK channel of from about 10 Gbps to about 100 Gbps. 
     
     
         7 . The single-channel unrepeatered system of  claim 6  wherein the OOK channel is 10 Gpbs, 20 Gbps, 30 Gbps, 40 Gbps, 50 Gbps, 60 Gbps, 70 Gbps, 80 Gbps, 90 Gbps, or 100 Gbps. 
     
     
         8 . The single-channel unrepeatered system of  claim 1  wherein the channel fiber bandwidth is broadened in a multiple of the fiber-native Brillouin bandwidth (20 MHz). 
     
     
         9 . The single-channel unrepeatered system of  claim 1  wherein the launched channel is pre-distorted to account for self-phase-modulation (SPM), intra-channel mixing, dispersive broadening and Raman-induced depletion. 
     
     
         10 . The single-channel unrepeatered system of  claim 9  wherein pre-distorting of the launched channel is performed by a method selected from the group consisting of: (i) inverting the solution of the nonlinear Schrödinger equation (NLSE) that describes single channel evolution over the unrepeatered link; (ii) implementing analytic approximation of a single channel evolution in a dispersive, lossy line; and (iii) choosing a choosing the specific bit-slot waveform shaping with highest stability with respect to nonlinear distortion, at given channel rate (speed) and launch power. 
     
     
         11 . The single-channel unrepeatered system of  claim 9  wherein pre-distorting of the launched channel is performed by selecting the solution order and subsequently pre-distorting the launch waveform to minimize nonlinear-dispersive distortion. 
     
     
         12 . The single-channel unrepeatered system of  claim 10  wherein pre-distorting of the launched channel is performed by inverting the solution of the nonlinear Schrödinger equation (NLSE) that describes single channel evolution over the unrepeatered link and wherein inversion of the NLSE occurs at the receiver when the launched wave comprises an undistorted bit stream (post-compensation) or the combination of two (pre- and post-distortion). 
     
     
         13 . The single-channel unrepeatered system of  claim 1  employing a parametric frequency comb. 
     
     
         14 . A multiple-channel unrepeatered system comprising:
 (a) a transmitter bank comprising multiple transmitters corresponding to a multitude of channels that are to be transmitted over the link generating and optionally pre-processing the information to be transmitted through the transmission link;   (b) a wavelength division multiplexer that joins the transmitters and launches them into the transmission link;   (c) a transmitting side amplification system;   (d) a transmission link devoid of any inline lumped amplifiers;   (e) a receiving side amplification system;   (f) a wavelength division de-multiplexer used to disjoin/separate the transmitted optical channels and route them to their corresponding receivers; and   (g) a plurality of receivers each of which is used to receive, process and detect the information on one or more channels transmitted to the transmission link.   
     
     
         15 . The multiple-channel unrepeatered system of  claim 14  wherein the information that is to be transmitted through the transmission link is pre-processed. 
     
     
         16 . The multiple-channel unrepeatered system of  claim 14  wherein the plurality of different receivers in step (g) is replaced or partially replaced by a multiple-channel processing receiver. 
     
     
         17 . The multiple-channel unrepeatered system of  claim 16  wherein the multiple-channel processing receiver replaces some of the plurality of receivers. 
     
     
         18 . The multiple-channel unrepeatered system of  claim 16  wherein the multiple-channel processing receiver replaces all of the plurality of receivers. 
     
     
         19 . The multiple-channel unrepeatered system of  claim 16  wherein the multiple-channel processing receiver performs coherent summing to discriminate noise and increase the received SNR. 
     
     
         20 . The multiple-channel unrepeatered system of  claim 14  wherein the system employs advanced higher-order Raman amplification designed to match increased signal launch power. 
     
     
         21 . The multiple-channel unrepeatered system of  claim 14  employing a parametric frequency comb. 
     
     
         22 . A multiple-channel unrepeatered system employing nonlinearity compensation comprising:
 (a) input data to be transmitted through the link;   (b) a nonlinearity pre-compensation block computing or estimating the waveform shapes to be imprinted onto the transmitted channels leading to the effective partial or complete cancellation of the nonlinear interaction in propagation;   (c) per wavelength-division multiplex channel computed waveforms;   (d) a bank of waveform generators used to imprint the channels' waveforms onto the transmitted optical field;   (e) a bank of corresponding optical transmitters;   (f) a wavelength division multiplexer joining the distinct transmitters and launching the generated channels into a single transmission link;   (g) a transmitter side optical amplification system;   (h) a transmission link devoid of inline lumped amplifiers;   (i) a receiver side optical amplification system;   (j) a wavelength division de-multiplexer used to separate the WDM channels and route them to their corresponding receivers;   (k) a plurality of receivers each of which being used to receive, process and detect the information on one or more channels transmitted to the transmission link;   (l) a nonlinearity post-compensating block used for partial or complete cancellation of the nonlinear interaction in propagation by processing the received information bearing waveforms or their sub-sampled versions; and   (m) received data obtained after processing away nonlinear impairment.   
     
     
         23 . The multiple-channel unrepeatered system of  claim 22  wherein the received data undergoes additional processing by at least one technique selected from the group consisting of clock recovery, carrier phase recovery, frequency offset removal, equalization, and error control decoding. 
     
     
         24 . The multiple-channel unrepeatered system of  claim 22  wherein a single channel information is copied to multiple carriers that occupy a set of wavelength-nondegenerate positions, or all transmitted wavelengths within the fiber transmission window. 
     
     
         25 . The multiple-channel unrepeatered system of  claim 22  wherein nonlinear distortion originating from intra-channel and inter-channel interaction is mitigated by a technique selected from the group consisting of: (a) inverting the NLSE that describes the interaction of all channels; (b) inverting the NLSE that describes the interaction of the channel subset; and (c) any other predistortion technique that relies on knowledge of fiber physical characteristics and channel bit-history. 
     
     
         26 . The multiple-channel unrepeatered system of  claim 22  wherein a subset of the channel information is copied to multiple carriers occupying a set of wavelength-nondegenerate positions within the fiber transmission window. 
     
     
         27 . The multiple-channel unrepeatered system of  claim 26  wherein the selection of fractional data information that needs to be distributed to a specific wavelength carrier is specifically performed in order to: (i) minimize nonlinear inter-channel interaction; and (ii) minimize the complexity of predistortion algorithm used to form the launch waveform or invert the NLSE at the receiver. 
     
     
         28 . The multiple-channel unrepeatered system of  claim 22  wherein the channel information is shared among all wavelength carriers but is encoded by different symbolic or physical means. 
     
     
         29 . The multiple-channel unrepeatered system of  claim 28  wherein the channel information is encoded by different symbolic means that include application of different forward-error correction codes (FEC) across the transmission window. 
     
     
         30 . The multiple-channel unrepeatered system of  claim 28  wherein the channel information is encoded by different physical means that include encoding distinct carriers by a wavelength-specific modulation format. 
     
     
         31 . The multiple-channel unrepeatered system of  claim 22  wherein the plurality of different receivers in step (k) is replaced or partially replaced by a multiple-channel processing receiver. 
     
     
         32 . The multiple-channel unrepeatered system of  claim 31  wherein the multiple-channel processing receiver replaces some of the plurality of receivers. 
     
     
         33 . The multiple-channel unrepeatered system of  claim 31  wherein the multiple-channel processing receiver replaces all of the plurality of receivers. 
     
     
         34 . The multiple-channel unrepeatered system of  claim 31  wherein the multiple-channel processing receiver can perform coherent summing to discriminate noise and increase the received SNR. 
     
     
         35 . The multiple-channel unrepeatered system of  claim 22  wherein the system employs advanced higher-order Raman amplification designed to match increased signal launch power. 
     
     
         36 . The multiple-channel unrepeatered system of  claim 22  employing a parametric frequency comb. 
     
     
         37 . A method for transmitting a signal by means of the single channel unrepeatered system of  claim 1  such that the transmitted signal is clearly received by a recipient in such a manner that the information original present in the signal is received by the recipient without significant distortion or loss. 
     
     
         38 . The method of  claim 37  wherein the transmitted signal is a digital signal representing text, a digital signal representing music, a digital signal representing video, a digital signal representing images, or a digital signal representing voice. 
     
     
         39 . A method for transmitting a signal by means of the multiple channel unrepeatered system of  claim 14  such that the transmitted signal is clearly received by a recipient in such a manner that the information original present in the signal is received by the recipient without significant distortion or loss. 
     
     
         40 . The method of  claim 39  wherein the transmitted signal is a digital signal representing text, a digital signal representing music, a digital signal representing video, a digital signal representing images, or a digital signal representing voice. 
     
     
         41 . A method for transmitting a signal by means of the multiple channel unrepeatered system of  claim 22  such that the transmitted signal is clearly received by a recipient in such a manner that the information original present in the signal is received by the recipient without significant distortion or loss. 
     
     
         42 . The method of  claim 41  wherein the transmitted signal is a digital signal representing text, a digital signal representing music, a digital signal representing video, a digital signal representing images, or a digital signal representing voice.