Flat optical frequency comb generation employing cascaded dual-drive Mach-Zehnder modulators

Abstract

The generation of flat optical frequency comb lines (OFCL) of 10 GHz frequency spacing is proposed and demonstrated theoretically employing Dual-Drive Mach Zehnder modulators (DD-MZMs). A theoretical analysis is carried out for ultra flat spectra due to single stage and cascading of DD-MZMs, which is confirmed by simulative results. Employing single DD-MZM, 19 OFCL with flatness 0 dB and 39 OFCL with flatness ≤ 1 dB have been generated at 11.16 Vπ−11.66 Vπ modulation voltages. 37 comb lines are obtained with 0 dB flatness and 49 OFCL with flatness ≤ 0.5 dB using two cascaded dual drive MZMs at 5.61 Vπ–6.11 Vπ–5.61 Vπ, 6.11 Vπ modulation voltages. Combining four DD-MZMs, 34 & 54 OFCL with flatness 0 dB and ≤ 0.5 dB is generated at modulation voltages 2.78 Vπ and 3.33 Vπ. Large numbers of OFCL with very high flatness are achieved by applying low RF voltage.

Keywords

• Cascaded DD-MZM
• Ultra flat OFCL
• Low driving voltages