Channel Performance Criteria in Optical Transport Systems with Forward Error Correcting Codes

In this paper we discuss the channel performance criteria in the optical transport networks (OTN)/dense wavelength division multiplexing (DWDM) networks with forward error correction (FEC) codes. The interdependent parameters used to evaluate the optical signal quality in OTN/DWDM channels are presented in this article: signal to noise ratio (SNR), optical signal to noise ratio (OSNR) and the Q-factor. The main role of FEC is to reduce the permissible the OSNR in the optical channel of OTN/DWDM systems. To monitor the status of optical channels, bit error rate (BER) on pre-FEC level of the receiving side of the optical channel can be used. By setting the appropriate threshold and interval of the error control at the pre-FEC level, the proactive actions can be taken even before the limit of FEC's error detection and correction capabilities is reached. In this article we presented our investigation of relationship between SNR/OSNR and Q-factor measurements.