Abstract: A method for the additional transmission of information items via a digital auxiliary channel in an optical wave guide system for digital signal transmission, in which system electric signals, which are coded in a pseudo-ternary bipolar code, are converted into a redundant, binary line code and are transmitted in converted form via an optical wave guide. In each case one information unit of the information items is transmitted by modification of a selected bit pattern from the data stream present in line code. According to the method, the pseudo-ternary bipolar code is the HDB-3 code, the MCMI code is used as the line code, the bit sequences 110011 and 001100 are used as selected bit patterns and at least one of the bit sequences 011011, 100111 and 101101 is allocated as a modification to the bit sequence 110011, and at least one of the bit sequences 001001, 000110 and 010010 is allocated as a modification to the bit sequence 001100.