Solution for hitless protection in high-speed OTN framer and front-end

In an optical communication system containing a primary line card and backup line card, a method comprising the steps of:

• providing interfaces for said primary line card and backup line card, each line card including a transmitter and receiver;
• and
• selecting output from said transmitter from either said primary or back up line card including selecting said backup line card when said primary line card encounters a failure;
• using a frame alignment signal (FAS) for frame aligning by using a FAS starting point detected by the primary line card as a reference and using a plurality of FAS checking elements each detecting different offset with one bit difference between each;
• and
• logically naming checking elements E-nto En, n being a bit skew tolerance, and E0 represents a primary element that detects signals starting from time t0+LF*tb, where LF is a number of bits in each frame and tb is the period of a single bit, Ei(iε[−n,n]) checks for the FAS from time t0+(LF+i)*tb;
• wherein said interfaces are synchronous, frame based and comprise a start sequence for each frame, said receiver having a primary frame start detecting module and other frame start detecting modules to work in parallel when said receiver enters a normal working mode, said receiver switching to a point of a frame start detected by another module if said primary start detecting module encounters a frame start loss.