It is observed that the reduced complexity minimum distance search method of Zehavi and Wolf (1987) can be extended from codes designed using the squared Euclidean distance measure to any measure which is additive over the code branches. C.N. Georghiades (1989) has derived such a metric for codes for the direct-detection optical channel. The search method is applied to find codes for four- and eight-point overlapping pulse position modulation (OPPM), with large minimum distance and a small number of codewords at that distance. >
['Gregory J. Pottie']
Trellis codes for the optical direct-detection channel