Patent ID: 8811827

Claim:
An apparatus, comprising: circuitry configured to receive a first plurality of electrical signals, each of which being modulated in accordance with a non-return-to-zero (NRZ) format, the circuitry further being configured to output a second plurality of electrical signals, each of which being modulated in accordance with an electrical return-to-zero (RZ) format, a phase of one of the first plurality of electrical signals being based on a timing of said one of the plurality of electrical signals and a timing of an input electrical signal; a first modulator configured to receive a first one of the second plurality of electrical signals, the first modulator outputting a first optical signal which is modulated in response to said first one of the second plurality of electrical signals, the first optical signal further being modulated in accordance an optical RZ format; a second modulator configured to receive a second one of the second plurality of electrical signals, the second modulator outputting a second optical signal which is modulated in response to said second one of the second plurality of electrical signals, the second optical signal further being modulated in accordance with the optical RZ format; a third modulator configured to receive a third one of the second plurality of electrical signals, the third modulator outputting a third optical signal which is modulated in response to said third one of the second plurality of electrical signals, the third optical signal further being modulated in accordance with the optical RZ format, the third optical signal being combined with the first optical signal; a fourth modulator configured to receive a fourth one of the second plurality of electrical signals, the fourth modulator outputting a fourth optical signal which is modulated in response to said fourth one of the second plurality of electrical signals, the fourth optical signal further being modulated in accordance with the optical RZ format, the fourth optical signal being combined with the second optical signal; and a multiplexer having a first input, a second input, and an output waveguide, the first input receiving the combined first and third optical signals and the second input receiving the combined second and fourth optical signals, the first, second, third, and fourth optical signals being combined onto the output waveguide, wherein the first optical signal carries first data including a first plurality of bits and a first plurality of RZ transitions, the third optical signal carries third data including a third plurality of bits and the first plurality of RZ transitions, the second optical signal carries second data including a second plurality of bits and a second plurality of RZ transitions, and the fourth optical signal carries fourth data including a fourth plurality of bits and the second plurality of RZ transitions, each of the first plurality of RZ transitions being temporally spaced from each of the second plurality of RZ transitions.