Method for increasing the probability of error correction in an optical communication channel
A method for improving the resilience of a communication channel (such as an optical communication channel) to correlated errors (e.g., burst errors), the channel is being formed by a time-multiplexed aggregation of a plurality of lower rate constituent lanes and employs a Forward Error-Correction (FEC) mechanism for forming codewords from data carried by the constituent lanes. Accordingly, the distribution of errors among the codewords is modified by introducing, at the transmitter side, specific delays to the transmission times via the constituent lanes, relative to each other.
1. A method for improving resilience of a communication channel being adapted to transfer data from a transmitter side to a receiver side and having a bandwidth, to correlated errors, said channel is being formed by a time-multiplexed aggregation of a plurality of lower rate constituent virtual lanes (VLs) that are distributed over a plurality of physical layer lanes, said physical layer lanes being divisions of said communication channel, said method comprising:
a) providing a Forward Error-Correction (FEC) mechanism at the receiver side, for reconstructing codewords from data carried by said physical layer lanes, to said receiver side, said FEC allowing a certain amount of errors to be acceptable in the physical layer lanes;
b) introducing, at said transmitter side, a specific delay to transmission times of each of said constituent VLs, the delays relative to each other, such that the transmission time of each constituent VL is delayed with respect to the transmission time of its preceding constituent VLs by said specific delay; and
c) distributing said constituent VLs over the physical layer lanes, thereby causing bits that are adjacent in said physical layer lanes to be recognized at the receiver side as originating from different bytes in each constituent VL, thereby distributing, by the FEC, said adjacent bits to different codewords.
2. The method according to claim 1 , wherein an original unmodified error distribution in the communication channel contains bursts or correlated errors caused by one or more of the following:
a) reducing the bandwidth of the communication channel;
b) employing a detection scheme at the receiver side, that generates correlated or burst errors.
3. The method according to claim 2 , wherein the detection scheme at the receiver side is a Decision Feedback Equalization.
4. The method according to claim 1 , wherein the communication channel employs “OTLk.n” signaling using Multi Lane Distribution (MLD), according to ITU-T Recommendation G.709.
5. The method according to claim 4 , wherein the communication channel is an OTN communication channel which employs a “Generic Forward Error Correction” (GFEC) mechanism, according to ITU-T Recommendation G.975.
6. The method according to claim 5 , wherein the lower rate constituent virtual lanes distributed over a single physical lane are delayed relative to each other by an amount of time corresponding to transmission of any value being between one and fifteen bytes.
7. The method according to claim 1 , wherein the correlated errors are burst errors.
8. The method according to claim 1 , wherein the communication channel is an optical communication channel.
9. The method according to claim 1 , wherein the bandwidth of the communication channel is reduced for Optical DuoBinary (ODB) modulation applications.
10. The method according to claim 1 , wherein a detection scheme at the receiver side is a Decision Feedback Equalization.