An N-carrier optical wavelength division modulator, WDM, transponder or transceiver (100; 400), comprising: at least two 10 Gb/s-class optical transmitters whose wavelengths are within a 50 or 100 GHz ITU-T window; an electronic control circuit configured to provide current for driving each 10 Gb/s-class optical transmitter, wherein said electronic control circuit includes a multiplexer configured to output a control signal, wherein each 10 Gb/s-class optical transmitter is driven by the electrical control signal output by the electronic control circuit according to a band-limited optical duo binary modulation technique at 20∼28 Gb/s; wherein the electronic control circuit further comprises: a forward-error-correction, FEC, device (110; 321; 521); at least one electronic input device configured to to convert a 10x10G electrical interface to N transmit lanes of 25-28 Gb/s differentially-encoded NRZ signals; N driver amplifiers (126a-b) configured to amplify the N lanes of 25-28 Gb/s NRZ signals, respectively, wherein the group delay variation of each amplifier is low enough so as not to distort the 25-28 Gb/s NRZ signals; N electronic low-pass filters (125a-b; 523a-d) configured to receive the amplified signals and serve as duobinary encoders; at least one electronic output device (422;522) configured to convert N receive lanes of 25∼28 Gb/s NRZ signals to a 10x10G electrical interface; wherein said at least two 10 Gb/s-class optical transmitters are further configured to convert the encoded signals into optical signals having N different wavelengths; wherein the WDM transponder or transceiver further comprises optical receivers. at least two 10 Gb/s-class optical transmitters whose wavelengths are within a 50 or 100 GHz ITU-T window; an electronic control circuit configured to provide current for driving each 10 Gb/s-class optical transmitter, wherein said electronic control circuit includes a multiplexer configured to output a control signal, wherein each 10 Gb/s-class optical transmitter is driven by the electrical control signal output by the electronic control circuit according to a band-limited optical duo binary modulation technique at 20∼28 Gb/s; wherein the electronic control circuit further comprises: a forward-error-correction, FEC, device (110; 321; 521); at least one electronic input device configured to to convert a 10x10G electrical interface to N transmit lanes of 25-28 Gb/s differentially-encoded NRZ signals; N driver amplifiers (126a-b) configured to amplify the N lanes of 25-28 Gb/s NRZ signals, respectively, wherein the group delay variation of each amplifier is low enough so as not to distort the 25-28 Gb/s NRZ signals; N electronic low-pass filters (125a-b; 523a-d) configured to receive the amplified signals and serve as duobinary encoders; at least one electronic output device (422;522) configured to convert N receive lanes of 25∼28 Gb/s NRZ signals to a 10x10G electrical interface; wherein said at least two 10 Gb/s-class optical transmitters are further configured to convert the encoded signals into optical signals having N different wavelengths; wherein the WDM transponder or transceiver further comprises optical receivers. a forward-error-correction, FEC, device (110; 321; 521); at least one electronic input device configured to to convert a 10x10G electrical interface to N transmit lanes of 25-28 Gb/s differentially-encoded NRZ signals; N driver amplifiers (126a-b) configured to amplify the N lanes of 25-28 Gb/s NRZ signals, respectively, wherein the group delay variation of each amplifier is low enough so as not to distort the 25-28 Gb/s NRZ signals; N electronic low-pass filters (125a-b; 523a-d) configured to receive the amplified signals and serve as duobinary encoders; at least one electronic output device (422;522) configured to convert N receive lanes of 25∼28 Gb/s NRZ signals to a 10x10G electrical interface; wherein said at least two 10 Gb/s-class optical transmitters are further configured to convert the encoded signals into optical signals having N different wavelengths; wherein the WDM transponder or transceiver further comprises optical receivers.