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-toback 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.
400-channel25-GHz spacing arrayed-waveguide grating COYering a full range of C-and L-bands? OFC 5. M. 1shii.A.Takaei.Y. Hida. M. Itoh. S. Kamei. 2001, Anaheim, WBZ, zoni. cascaded spot-size converter" OECCIIOOC 6 . M. 1toh.T. Saida,Y. Hida, M. 1shii.Y. Inoue,Y. 0 Z N 1 , Sydney, PDt-I, 2001. 0 32 64 96 128 160 192 224 256Hihino. and A. Sueita. 'Low-loss 1.5% A ar-Channel numbsr " rayed waveguide grating with spot-size converters," ECOC '01. Amsterdam, Mo.F.2.3, ThC6 Fig. 7. Losses of 256-channel AWG chip and module after packaging.
2001.Himena andY. Ohmori,"Fabrication of very spectral efficiency has been limited. In this paper, we propose and experimentally demonstrate a novel scheme for WDM systems to overcome the spectral efficiency limitation. It is well known that orthogonal frequency division multiplexing provides high spectral efficiency in a wireless communication system.' However, the complicated demultiplexkg scheme, mostly digital processing, is difficult to use in the optical frequency domain. Our proposed scheme applies this concept to an optical communication field. We also propose the use of an optical discrete Fourier transformer to accomplish separation. The transformer is implemented by filtering the neighboring signals in the time and frequency domains. The scheme allows theoverlap ofthespectrumofneighboringchannels and can eliminate the coherent crosstalk
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