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ABSTRACT: We report a 160 Gbit/s single-channel OTDM transmission in the 1.1 μm band using a high-Δ single-mode step-index fiber (SIF) and ytterbium-doped fiber amplifiers (YDFAs). The 160 Gbit/s OTDM signal was generated from a 10 GHz mode-locked Yb fiber laser. The dispersion and dispersion slope of the SIF were precisely compensated with a chirped fiber Bragg grating (FBG) and a pre-chirping technique, respectively. A nonlinear optical loop mirror (NOLM) was employed to demultiplex the 160 Gbit/s OTDM signal to 10 Gbit/s. As a result, we achieved a 100 km transmission with a BER of < 10<sup>-9</sup> and a 300 km transmission with a BER of < 10<sup>-3</sup>, which is below the standard FEC limit at a net bit rate of 149.5 Gbit/s taking the 7% FEC overhead into account.
Optics Express 02/2013; 21(4):4303-4310. · 3.59 Impact Factor
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ABSTRACT: We demonstrate a marked performance improvement in a 512 QAM transmission by employing frequency-domain equalization (FDE) instead of an FIR filter. FDE enables us to compensate for distortions due to hardware imperfections in the transmitter with higher precision, which successfully reduced the power penalty by 4 dB in a 54 Gbit/s (3 Gsymbol/s)-160 km transmission. FDE also allows the transmission distance to be extended up to 240 km.
Optics Express 10/2012; 20(21):23383-9. · 3.59 Impact Factor
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ABSTRACT: We report a substantial increase in the heat resistance in a connector-type single-wall carbon nanotube (SWNT) saturable absorber by sealing SWNT/P3HT composite with siloxane. By applying the saturable absorber to a passively mode-locked Er fiber laser, we successfully demonstrated 280 fs, 31 mW pulse generation with a fivefold improvement in heat resistance.
Optics Express 10/2012; 20(21):23659-65. · 3.59 Impact Factor
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ABSTRACT: We demonstrate substantial performance improvements in 256 QAM transmission in terms of both data rate and distance that we realized by using a digital back-propagation (DBP) method. 160 Gbit/s-160 km and 64 Gbit/s-560 km transmissions were successfully achieved with a polarization-multiplexed 256 QAM signal, in which the symbol rate and transmission distance were greatly increased by compensating for the interplay between dispersion and nonlinearity, which is responsible for the transmission impairment especially for a higher symbol rate and longer distance.
Optics Express 08/2012; 20(18):19815-21. · 3.59 Impact Factor
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ABSTRACT: We propose and demonstrate a new technique for measuring mode couplings along a multi-core fiber (MCF) that employs a multi-channel optical time domain reflectometer (OTDR). The mode couplings along seven core fibers are successfully obtained using a synchronous seven-channel OTDR.
Optics Express 05/2012; 20(11):12530-40. · 3.59 Impact Factor
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ABSTRACT: A novel coherent multi-level OTDM transmission scheme is presented by using an RZ-CW conversion technique in a coherent receiver, in which the transmitted coherent RZ pulses are OTDM demultiplexed and converted into a CW signals for demodulation with a CW-LO. This scheme enables us to achieve a high SNR demodulation and demultiplexing performance even for ultrahigh-speed OTDM signals with ultra multi-level modulation, which would be difficult to realize with a conventional scheme of simultaneous demodulation and demultiplexing using a pulsed-LO. The advantage of this scheme is successfully demonstrated with 10 Gsymbol/s, 4- and 8-OTDM, 32-RZ/QAM demodulation experiments.
Optics Express 12/2011; 19(26):B574-80. · 3.59 Impact Factor
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ABSTRACT: We report a 10 GHz harmonically and regeneratively mode-locked Yb fiber laser with a phase-locked loop (PLL) technique at 1.1 μm. Stable mode locking was achieved by optimizing the average dispersion of the fiber cavity to an anomalous dispersion to operate as a soliton laser. As a result, a 1.1 ps optical pulse with a timing jitter of 140 fs was successfully generated.
Optics Express 12/2011; 19(25):25426-32. · 3.59 Impact Factor
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ABSTRACT: We demonstrate a 10-Gbit/s transmission over a 5-km photonic crystal fiber in the 1.1 μm band using a directly-modulated single-mode VCSEL. The transmission distance was extended to 14 km by using an ytterbium-doped fiber amplifier.
03/2010;
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ABSTRACT: We demonstrate parabolic optical pulse generation by manipulating the intensity and phase of individual longitudinal modes of a 40 GHz picosecond optical pulse train in the spectral domain. Bright and dark parabolic pulses were generated from a 40 GHz mode-locked fiber laser using a 64-channel arrayed waveguide grating pulse shaper. The obtained parabolic pulse, which can easily generate a linear chirping, is useful for a number of applications to optical signal processing applications, including pulse compression and time-domain optical Fourier transformation.
Optics Letters 06/2008; 33(10):1102-4. · 3.40 Impact Factor
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ABSTRACT: A straight-line 160 Gbit/s-900 km DPSK transmission was successfully demonstrated with time-domain optical Fourier transformation without employing polarization multiplexing or Raman amplification. The transmission performance was almost ASE limited due to in-line EDFAs.
Optical Communication (ECOC), 2007 33rd European Conference and Ehxibition of; 10/2007
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ABSTRACT: We report saturable absorber materials in the 1.5 microm band that consist of poly-methyl-methacrylate (PMMA) and polystyrene (PS) polymers with single-wall carbon nanotubes (SWNTs). A very uniform dispersion of SWNT in PMMA and PS polymers has been realized by using chlorobenzene or tetrahydrofuran as a dispersion solvent. These materials, which are as thick as 1 mm, are easily optically polished on both surfaces. This was difficult to achieve with previous thin-film materials. By incorporating PMMA/SWNT as a saturable absorber, a 171 fs pulse is successfully generated in a passively mode-locked fiber laser.
Optics Letters 05/2006; 31(7):915-7. · 3.40 Impact Factor
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ABSTRACT: A 40-GHz, 100-fs pulse train was successfully generated by soliton compression of a mode-locked laser diode (MLLD) pulse with a dispersion-decreasing fiber. The MLLD had a longitudinal mode linewidth as broad as 60 MHz, which made it possible to suppress stimulated Brillouin scattering and achieve stable, ultrahigh-speed pulse compression without applying external frequency modulation.
Optics Letters 04/2005; 30(6):670-2. · 3.40 Impact Factor
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ABSTRACT: We report that stimulated Brillouin scattering (SBS) in a dispersion-decreasing fiber (DDF) is particularly disadvantageous with ultrahigh-speed femtosecond soliton compression that exceeds 40 GHz. It is important to note that the increase in the longitudinal mode power of a soliton is proportional to the square of the repetition rate. The SBS threshold is determined by the dispersion-decreasing rate of the DDF, rather than its fiber loss. We suppressed the SBS by applying 30-MHz frequency modulation to a mode-locked fiber laser and successfully obtained a stable 40-GHz, 100-fs pulse train.
Optics Letters 03/2005; 30(4):364-6. · 3.40 Impact Factor
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ABSTRACT: We propose a new method for generating a parabolic pulse by use of a dispersion-decreasing fiber with normal group-velocity dispersion. When a hyperbolic dispersion-decreasing structure is employed, the pulse evolves into a linearly chirped pulse with an exact parabolic intensity profile without radiating dispersive waves. The highly linear chirp in the parabolic pulse allows for efficient and high-quality pulse compression.
Optics Letters 04/2004; 29(5):498-500. · 3.40 Impact Factor
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ABSTRACT: Incomplete collisions in wavelength-division-multiplexed return-to-zero transmission systems are analyzed by asymptotic methods. Formulas for frequency and timing shifts are obtained. The results agree with direct numerical calculations.
Optics Letters 08/2003; 28(14):1191-3. · 3.40 Impact Factor
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ABSTRACT: The frequency and timing shifts associated with dispersion-managed solitons in a wavelength-division multiplexed system are computed by the numerically efficient Poisson sum technique. Analytical formulas are attainable by use of this approach with a Gaussian approximation for the soliton. The results are favorably compared with known results for the frequency shift. The method also applies to quasi-linear return-to-zero transmission formats.
Optics Letters 04/2002; 27(5):318-20. · 3.40 Impact Factor
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ABSTRACT: Energy transfer between adjacent pulses as a result of nonlinear intrachannel interactions in a transmission system with strong periodic dispersion management is analyzed. With small average dispersion, the energy change between nonzero bits grows linearly with respect to distance in the presence of loss and lumped amplification, whereas in a lossless system the energy change is found to be significantly suppressed. The analytical results compare favorably with the results of direct numerical simulation of the full system.
Optics Letters 03/2002; 27(3):203-5. · 3.40 Impact Factor
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ABSTRACT: Ultrahigh-speed fiber lasers operating at up to 40 GHz offer a clean longitudinal comb and a narrow linewidth. This makes them suitable for applications including optical comb generation, ultrahigh-speed optical pulse transmission including PSK, and as opto-microwave oscillators. In this paper, we describe recent progress on ultrafast fiber lasers and their applications to optical metrology.
