50-Gb/s Direct Modulation of a 1.3-μm InGaAlAs-Based DFB Laser With a Ridge Waveguide Structure

• Published in: IEEE journal of selected topics in quantum electronics Vol. 19; no. 4; p. 1500908
• Main Authors: Kobayashi, W., Ito, T., Yamanaka, T., Fujisawa, T., Shibata, Y., Kurosaki, T., Kohtoku, M., Tadokoro, T., Sanjoh, H.
• Format: Journal Article
• Language: English
• Published: IEEE 01-07-2013
• Subjects: Bandwidth; Cavity resonators; Damping; Direct modulation; directly modulated laser (DML); distributed-feedback (DFB) lasers; Frequency response; InGaAlAs; Resistance; ridge waveguide structure; Temperature measurement; Waveguide lasers
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/JSTQE.2013.2238509

We demonstrate 50-Gb/s direct modulation by using 1.3-μm distributed-feedback lasers with a ridge waveguide structure. We employed InGaAlAs material for a multiple-quantum well to obtain a low damping factor K , and fabricated a ridge waveguide structure buried in benzocyclobutene to realize a structure with a low parasitic capacitance. In addition, to obtain high maximum frequency relaxation oscillations fr, we designed the cavity length L ), and achieved a 3-dB-down frequency bandwidth of 34 GHz. We realized 50-Gb/s clear eye openings with a back-to-back configuration, and achieved a mean output power of over 5.0 dBm, and a dynamic extinction ratio of 4.5 dB. We measured the 50-Gb/s transmission characteristics, and obtained clear eye openings for transmissions over 20-, 40-, and 60-km single-mode fibers (SMF). We also measured the bit-error-rate performance, and obtained an error-free operation and a power penalty of less than 0.5 dB after a 10-km SMF transmission.