  We analyze a class of high performance, low decoding-data-flow
error-correcting codes suitable for high bit-rate optical-fiber communication
systems. A spatially-coupled split-component ensemble is defined, generalizing
from the most important codes of this class, staircase codes and braided block
codes, and preserving a deterministic partitioning of component-code bits over
code blocks. Our analysis focuses on low-complexity iterative algebraic
decoding, which, for the binary erasure channel, is equivalent to a
generalization of the peeling decoder. Using the differential equation method,
we derive a vector recursion that tracks the expected residual graph evolution
throughout the decoding process. The threshold of the recursion is found using
potential function analysis. We generalize the analysis to mixture ensembles
consisting of more than one type of component code, which provide increased
flexibility of ensemble parameters and can improve performance. The analysis
extends to the binary symmetric channel by assuming mis-correction-free
component-code decoding. Simple upper-bounds on the number of errors
correctable by the ensemble are derived. Finally, we analyze the threshold of
spatially-coupled split-component ensembles under beyond bounded-distance
component decoding.
