A method of encapsulating digital communications traffic for transmission on an optical link, the method comprising: a. receiving an input digital communications signal having an input line code ; b. performing clock and data recovery on the input digital communications signal to obtain input line coded digital communications traffic and a recovered clock signal ; c. decoding the input digital communications traffic to obtain information bits and non-information bits ; d. removing decoded non-information bits ; e. adding service channel bits for monitoring or maintenance ; f. assembling the service channel bits and information bits into frames , wherein forward error correction is applied to the information bits and to the service channel bits using a plurality of interleaved forward error correction codecs each configured to apply a preselected forward error correction code, and wherein a maximum acceptable latency to be added by the forward error correction is obtained and said plurality of forward error correction codecs is selected such that a latency added by the forward error correction is not greater than the maximum acceptable latency ; and g. line coding the assembled frames using an output line code to form an encapsulated digital communications signal for transmission on an optical link , wherein steps c. to g. are performed using the timing of the recovered clock signal to transmit the input digital communications signal into the optical line. a. receiving an input digital communications signal having an input line code ; b. performing clock and data recovery on the input digital communications signal to obtain input line coded digital communications traffic and a recovered clock signal ; c. decoding the input digital communications traffic to obtain information bits and non-information bits ; d. removing decoded non-information bits ; e. adding service channel bits for monitoring or maintenance ; f. assembling the service channel bits and information bits into frames , wherein forward error correction is applied to the information bits and to the service channel bits using a plurality of interleaved forward error correction codecs each configured to apply a preselected forward error correction code, and wherein a maximum acceptable latency to be added by the forward error correction is obtained and said plurality of forward error correction codecs is selected such that a latency added by the forward error correction is not greater than the maximum acceptable latency ; and wherein forward error correction is applied to the information bits and to the service channel bits using a plurality of interleaved forward error correction codecs each configured to apply a preselected forward error correction code, and wherein a maximum acceptable latency to be added by the forward error correction is obtained and said plurality of forward error correction codecs is selected such that a latency added by the forward error correction is not greater than the maximum acceptable latency ; and g. line coding the assembled frames using an output line code to form an encapsulated digital communications signal for transmission on an optical link , <EOS>