Flattened optical frequency-locked multi-carrier generation by cascading one EML and one phase modulator driven by different RF clocks

• We propose a novel scheme for optical frequency-locked multi-carrier generation based on one EML and one PM in cascade driven by different sinusoidal RF clocks.
• We experimentally demonstrate 25 optical subcarriers with frequency spacing of 12.5 GHz and power difference less than 5 dB can be generated, which agrees well with the corresponding numerical simulation.
• The PDM-QPSK modulated coherent optical transmission demonstration is also carried out based on one of the 25 generated subcarriers by the cascaded EML and PM.
• Our results well demonstrate the feasibility of our proposed scheme for optical multi-carrier generation and PDM-QPSK modulated coherent optical transmission.

We propose a novel scheme for optical frequency-locked multi-carrier generation based on one electro-absorption modulated laser (EML) and one phase modulator (PM) in cascade driven by different sinusoidal radio-frequency (RF) clocks. The optimal operating zone for the cascaded EML and PM is found out based on theoretical analysis and numerical simulation. We experimentally demonstrate 25 optical subcarriers with frequency spacing of 12.5 GHz and power difference less than 5 dB can be generated based on the cascaded EML and PM operating in the optimal zone, which agrees well with the numerical simulation. We also experimentally demonstrate 28-Gbaud polarization division multiplexing quadrature phase shift keying (PDM-QPSK) modulated coherent optical transmission based on the cascaded EML and PM. The bit error ratio (BER) can be below the pre-forward-error-correction (pre-FEC) threshold of 3.8 × 10−3 after 80-km single-mode fiber-28 (SMF-28) transmission.