An apparatus comprising: a digital signal processing, DSP, unit configured to perform fiber dispersion pre-compensation on a digital signal sequence based on a dispersion value to produce a pre-compensated signal, wherein the dispersion value is associated with a remote optical receiver; a plurality of digital-to-analog converters, DACs, coupled to the DSP unit and configured to convert the pre-compensated signal into analog electrical signals; and a frontend coupled to the DACs and configured to: convert the analog electrical signals into a first optical signal; characterized in that the method further comprises: add a constant optical electric-field to the first optical signal to produce a second optical signal; and transmit the second optical signal to the remote optical receiver, wherein the dispersion value is a value that is opposite to an amount of chromatic dispersion, CD, associated with the remote optical receiver, and the first optical signal comprises a plurality of light pulses carrying the digital signal sequence, wherein the CD causes the light pulses to broaden by a pulse broadening duration, and wherein the DSP unit is configured to: insert a first guard interval,GI, before the digital signal sequence; and insert a second GI after the digital signal sequence, wherein the first GI and the second GI each comprises a duration greater than the pulse broadening duration. a digital signal processing, DSP, unit configured to perform fiber dispersion pre-compensation on a digital signal sequence based on a dispersion value to produce a pre-compensated signal, wherein the dispersion value is associated with a remote optical receiver; a plurality of digital-to-analog converters, DACs, coupled to the DSP unit and configured to convert the pre-compensated signal into analog electrical signals; and a frontend coupled to the DACs and configured to: convert the analog electrical signals into a first optical signal; characterized in that the method further comprises: add a constant optical electric-field to the first optical signal to produce a second optical signal; and transmit the second optical signal to the remote optical receiver, wherein the dispersion value is a value that is opposite to an amount of chromatic dispersion, CD, associated with the remote optical receiver, and the first optical signal comprises a plurality of light pulses carrying the digital signal sequence, wherein the CD causes the light pulses to broaden by a pulse broadening duration, and wherein the DSP unit is configured to: insert a first guard interval,GI, before the digital signal sequence; and insert a second GI after the digital signal sequence, wherein the first GI and the second GI each comprises a duration greater than the pulse broadening duration. add a constant optical electric-field to the first optical signal to produce a second optical signal; and transmit the second optical signal to the remote optical receiver, wherein the dispersion value is a value that is opposite to an amount of chromatic dispersion, CD, associated with the remote optical receiver, and the first optical signal comprises a plurality of light pulses carrying the digital signal sequence, wherein the CD causes the light pulses to broaden by a pulse broadening duration, and wherein the DSP unit is configured to: insert a first guard interval,GI, before the digital signal sequence; and insert a second GI after the digital signal sequence, wherein the first GI and the second GI each comprises a duration greater than the pulse broadening duration. insert a first guard interval,GI, before the digital signal sequence; and insert a second GI after the digital signal sequence, wherein the first GI and the second GI each comprises a duration greater than the pulse broadening duration.