An all-optical modulation format converter for converting optical data signals modulated in an on-off-keying format to a phase-shift-keying format. The method further includes selecting potential hypothetical paths of potential words in the first and second segments that cross the boundary. Particular aspects of the present invention are described in the claims, specification and drawings. The concave groove comprises a base surface opposite to a lateral surface of the connector and second inclined portions opposite to first inclined portions of the connector, respectively. The processor processes such interactions, and generates an interaction descriptor for each interaction.