1-11hit |
Hideyuki SOTOBAYASHI Kazuro KIKUCHI
This paper analyzes pulse characteristics of actively mode-locked fiber lasers by including the group-velocity dispersion and the Kerr nonlinearity of the fiber, both of which have not been taken into account in the conventional theory of mode locking. We show that chirped sech pulses are generated from nonlinear and dispersive fiber lasers. By considering the stability of the laser, we also derive design rules for the generation of ultra-short pulses.
Sze Yun SET Chee Seong GOH Kazuro KIKUCHI
The generation of high repetition-rate optical pulse train using a passively mode-locked figure-8 fiber ring laser is presented. The laser employs a novel configuration incorporating a superstructure fiber Bragg grating. Pulse train with repetition rates up to 100GHz is possible and transform-limited pulses with pulsewidth below 1ps can be achieved with chirp compensation. The output pulses can further be reduced to 83fs with an external pulse compressor.
Fumio FUTAMI Yuichi TAKUSHIMA Kazuro KIKUCHI
Aiming at wideband and flat supercontinuum generation (SC) from optical fibers in the 1.55-µm wavelength region, we study both experimentally and theoretically how SC spectra are influenced by group-velocity dispersion (GVD) of fibers. In the anomalous GVD region, since the peak power of pump pulses is kept high during propagation through the fiber by the higher-order soliton effect, the Raman effect has an adverse effect to flat and wideband SC generation. In the zero GVD region, the interplay of the third-order dispersion (TOD) and the self-phase modulation splits the SC spectrum into two main components. On the other hand, in the normal GVD region, nevertheless the SC spectrum broadens wider and smoother than those in anomalous and zero GVD regions, it is still asymmetric when TOD of the fiber can not be ignored. From these results, we find that a dispersion-flattened fiber with normal GVD is the most suitable for flat and wideband SC generation. A 280-nm wide SC spectrum with the spectral-density fluctuation less than 10 dB is actually generated from such a fiber.
Fumio FUTAMI Yuichi TAKUSHIMA Kazuro KIKUCHI
Aiming at wideband and flat supercontinuum generation (SC) from optical fibers in the 1.55-µm wavelength region, we study both experimentally and theoretically how SC spectra are influenced by group-velocity dispersion (GVD) of fibers. In the anomalous GVD region, since the peak power of pump pulses is kept high during propagation through the fiber by the higher-order soliton effect, the Raman effect has an adverse effect to flat and wideband SC generation. In the zero GVD region, the interplay of the third-order dispersion (TOD) and the self-phase modulation splits the SC spectrum into two main components. On the other hand, in the normal GVD region, nevertheless the SC spectrum broadens wider and smoother than those in anomalous and zero GVD regions, it is still asymmetric when TOD of the fiber can not be ignored. From these results, we find that a dispersion-flattened fiber with normal GVD is the most suitable for flat and wideband SC generation. A 280-nm wide SC spectrum with the spectral-density fluctuation less than 10 dB is actually generated from such a fiber.
Xiaomin WANG Kazuro KIKUCHI Yuichi TAKUSHIMA
We analyze the dispersion-managed optical transmission system for the non-return-to-zero (NRZ) pulse format. First, we investigate the physical image of dispersion management by computing small-signal-based transfer functions, and summarize the dependence of transmission performance on system parameters. Next, the Q-map is computed numerically to design long-distance large-capacity dispersion-managed transmission systems for a single channel in a more detailed manner. It is shown that the third-order dispersion of fibers negatively influences transmission performance, and third-order dispersion compensation is proved to be an effective method for extending the transmission distance of high bit-rate systems. Utilizing these results, guidelines can be derived for the optimal design of long-distance large-capacity NRZ transmission systems.
Chee Seong GOH Sze Yun SET Kazuro KIKUCHI
We report tunable optical devices based on fiber Bragg gratings (FBGs), whose filtering characteristics are controlled by strain distributions. These devices include a widely wavelength tunable filter, a tunable group-velocity dispersion (GVD) compensator, a tunable dispersion slope (DS) compensator, and a variable-bandwidth optical add/drop multiplexer (OADM), which will play important roles for next-generation reconfigurable optical networks.
Yasuyuki OZEKI Yuichi TAKUSHIMA Keiichi AISO Kazuro KIKUCHI
We design and demonstrate a high repetition-rate similariton generation system using normal dispersion fiber amplifiers (NDFA's). We numerically calculate the pulse evolution in NDFA's and clarify the condition to generate similariton pulses in a finite-length NDFA. Then we design the similariton generation system in consideration of the use of Erbium-doped fibers (EDF's) and show that a km-long fiber amplifier with low normal dispersion can generate a high repetition-rate similariton train from practical pico-second pulse sources. In the experiment, we demonstrate a 10-GHz similariton source using a 1.2-km-long EDF. For application to multi-wavelength light sources, we measure the bit-error rate of the spectrally sliced similariton, and show that it exhibits low-noise performance, which is attributed to the spectral flatness.
Kazuro KIKUCHI Junichi YOSHIDA
Kazuro KIKUCHI Junichi YOSHIDA
Xiaomin WANG Kazuro KIKUCHI Yuichi TAKUSHIMA
We analyze the dispersion-managed optical transmission system for the non-return-to-zero (NRZ) pulse format. First, we investigate the physical image of dispersion management by computing small-signal-based transfer functions, and summarize the dependence of transmission performance on system parameters. Next, the Q-map is computed numerically to design long-distance large-capacity dispersion-managed transmission systems for a single channel in a more detailed manner. It is shown that the third-order dispersion of fibers negatively influences transmission performance, and third-order dispersion compensation is proved to be an effective method for extending the transmission distance of high bit-rate systems. Utilizing these results, guidelines can be derived for the optimal design of long-distance large-capacity NRZ transmission systems.