Multi-rate transparent mux for optical communications networks

Abstract

Bit-transparent muxing of an input signal for transport through an optical communications network. A fixed length container of the optical communications network is defined, which includes an overhead and a payload. A stuffing ratio (α) is based on a line rate of the input signal and a data rate of the container. A number (N FS ) of fixed stuffs is computed based on the stuffing ratio (α). The input signal and N FS fixed stuffs are inserted into the payload of the container, and the computed number N FS stored in the container's overhead. In some embodiments, the container is an overclocked OTU-3 (OTU3+) frame having a line rate of 44.6 Gb/s. This enables bit-transparent mux/demux of four nominal 10-Gig signals having line rates within a range of between 7.6 Gb/s and 10.4 Gb/s, or a single nominal 40-Gig signal having a line rate within a range of between 38.8 Gb/s and 41.6 Gb/s.

We claim: 
     
         1 . A non-transitory processor-readable medium having instructions for execution by at least one processor of a network interface for transparently multiplexing a client signal into a fixed-length container for transport through an optical communications network coupled to the network interface, the instructions comprising:
 instructions executable by the at least one processor to compute a stuffing ratio (α) based on a line rate of the client signal and a payload capacity of the container;   instructions executable by the at least one processor to compute a number (N FS ) of fixed stuffs based on the stuffing ratio (α);   instructions executable by the at least one processor to insert N FS  fixed stuffs into a payload of the container;   instructions executable by the at least one processor to insert bytes of the client signal into a residual portion of the payload of the container; and   instructions executable by the at least one processor to store the computed number N FS  in a predetermined location of the container.   
     
     
         2 . The non-transitory processor-readable medium of  claim 1 , wherein the container is a logical Optical Transport Network (OTN) container. 
     
     
         3 . The non-transitory processor-readable medium of  claim 2 , wherein the container has a line rate based on an optimum cost/bit/km of the optical communications network. 
     
     
         4 . The non-transitory processor-readable medium of  claim 2 , wherein the predetermined location of the container comprises at least one unallocated field of the container overhead. 
     
     
         5 . The non-transitory processor-readable medium of  claim 1 , wherein the computed number N FS  of fixed stuffs is represented by a pair of values (FS1 and FS2), respectively associated with integer and fractional components of the number N FS . 
     
     
         6 . The non-transitory processor-readable medium of  claim 5 , wherein the instructions executable to insert N FS  fixed stuffs into the payload comprise:
 instructions executable by the at least one processor to insert the integer component value (FS1) of the number of fixed stuffs into the payload; and   instructions executable by the at least one processor to insert an additional fixed stuff into the payload of each Nth container, where N=1/FS2.   
     
     
         7 . The non-transitory processor-readable medium of  claim 5 , wherein the instructions executable to insert N FS  fixed stuffs into the payload comprise:
 instructions executable by the at least one processor to insert the integer component value (FS1) of the number of fixed stuffs into the payload;   instructions executable by the at least one processor to represent the fractional component (FS2) as a byte value; and   instructions executable by the at least one processor to insert an additional fixed stuff into the payload of each Nth container for each bit FS2[i], 0<i<7, having a value of binary “1”, where N=28−i.   
     
     
         8 . The non-transitory processor-readable medium of  claim 1 , wherein the container payload is divided into two or more sectors, and wherein the instructions executable to compute the stuffing ratio (α), to compute the number (N FS ) of fixed stuffs, to insert N FS  fixed stuffs into the payload of the container, to insert bytes of the client signal into the residual portion of the payload of the container, and to store the computed number N FS  are configured to be executed for each sector. 
     
     
         9 . The non-transitory processor-readable medium of  claim 8 , wherein the sectors are of equal size. 
     
     
         10 . The non-transitory processor-readable medium of  claim 8 , wherein a size of at least one sector differs from a size of at least one other sector. 
     
     
         11 . A non-transitory processor-readable medium having instructions for execution by at least one processor of a network interface for transparently multiplexing a plurality of client signals into a fixed-length container for transport through an optical communications network coupled to the network interface, the instructions comprising:
 instructions executable by the at least one processor to subdivide a payload of the fixed length container into sectors, and to assign each of the plurality of client signals to a respective one of the sectors;   instructions executable by the at least one processor to compute, for each client signal and its respective sector, a respective number (N FS ) of fixed stuffs based on the nominal line rate of the client signal and a payload capacity of the respective sector;   instructions executable by the at least one processor to insert bytes of each client signal together with its respective number N FS  of fixed stuffs into each respective sector of the payload of the container; and   instructions executable by the at least one processor to insert the computed numbers N FS  in predetermined locations of the container.   
     
     
         12 . The non-transitory processor-readable medium of  claim 11 , wherein each client signal has a respective line rate that varies around a nominal line rate, the instructions comprising:
 instructions executable by the at least one processor to compute the number (N FS ) of fixed stuffs based on the respective nominal line rate of each client signal and a payload capacity of the respective sector;   instructions executable by the at least one processor to compute a respective variable number of stuff bytes required to keep each respective client signal aligned with its respective sector; inserting bytes of each respective client signal together with its respective number N FS  of fixed stuffs and its respective variable number of stuff bytes into a payload of its respective sector; and   instructions executable by the at least one processor to insert each respective computed number N FS  and each respective computed variable number of stuff bytes in predetermined locations of each respective sector.   
     
     
         13 . The non-transitory processor-readable medium of  claim 11 , wherein the container is a logical Optical Transport Network (OTN) container. 
     
     
         14 . The non-transitory processor-readable medium of  claim 11 , wherein the predetermined locations of the container comprise unallocated fields of container overhead. 
     
     
         15 . The non-transitory processor-readable medium of  claim 11 , wherein each respective number N FS  of fixed stuffs is represented as a respective integer component value FS1 of fixed stuffs and a fractional component value FS2 of fixed stuffs, and the instructions executable to insert the respective number N FS  fixed stuffs into each respective sector of the payload of the container comprise:
 instructions executable by the at least on processor to insert the respective integer component value FS1 of fixed stuffs into each respective sector of the payload; and   instructions executable by the at least one processor to insert an additional fixed stuff into the respective sector of the payload of each Nth container, where N=1/FS2.   
     
     
         16 . A non-transitory processor-readable medium having instructions for execution by at least one processor of a network interface for transparently multiplexing a client signal into a fixed-length container for transport through an optical communications network coupled to the network interface, the instructions comprising:
 instructions executable by the at least one processor to compute a number (N FS ) of fixed stuffs based on a nominal line rate of the client signal and a payload capacity of the container;   instructions executable by the at least one processor to compute a variable number of stuff bytes required to keep the client signal aligned with the fixed length container;   instructions executable by the at least one processor to insert bytes of the client signal together with N FS  fixed stuffs and the variable number of stuff bytes into a payload of the container; and   instructions executable by the at least one processor to insert the computed number N FS  and the computed variable number of stuff bytes in predetermined locations of the container.   
     
     
         17 . The non-transitory processor-readable medium of  claim 16 , wherein the container is a logical Optical Transport Network (OTN) container. 
     
     
         18 . The non-transitory processor-readable medium of  claim 16 , wherein the predetermined locations of the container comprise unallocated fields of container overhead. 
     
     
         19 . The non-transitory processor-readable medium of  claim 16 , wherein:
 the number N FS  of fixed stuffs is represented as an integer component value FS1 of fixed stuffs and a fractional component value FS2 of fixed stuffs, and the instructions executable to insert the number N FS  fixed stuffs into the payload of the container comprise:
 instructions executable by the at least one processor to insert the integer component value FS1 of fixed stuffs into the payload; and 
   instructions executable by the at least one processor to insert an additional fixed stuff into the payload of each Nth container, where N=1/FS2.