We report a coherent driver modulator sub-assembly for 100-Gbaud class transmitter. The sub-assembly employs a codesigned high-speed driver IC and optical modulator, where the designs for the characteristic impedance between the driver IC and IQ modulator and for the RF pads are optimized. The EO bandwidth is over 67 GHz. This response is sufficient for 100-Gbaud-class operation even if we consider RF losses caused by a package, PCB, and DAC. We also demonstrated QPSK and 16-QAM at the speed of 128 and 112 Gbaud, respectively.
We report Nyquist-wavelength-division-multiplexed (Nyquist-WDM) seven-channel 192-Gb/s polarization-divisionmultiplexed
16-QAM transmission. The transmitter comprises high-speed digital-to-analog converters (DACs)
fabricated with 0.5-μm indium phosphide (InP) heterojunction bipolar transistors and an FPGA-based multi-channel
digital signal generator, and enables us to perform transmitter-side digital signal processing (DSP) for spectrally efficient
WDM transmission. The transmitter generated 24-Gbaud electrical waveforms for optical 16-QAM signals with a digital
pre-filter. Using low-loss and low-nonlinear pure silica core fiber, we achieved 25-GHz-spaced seven-channel 192 Gb/s
transmission distance of 480 km with a spectral efficiency of 7.17 b/s/Hz.
Proc. SPIE. 7960, Coherent Optical Communication: Components, Subsystems, and Systems
KEYWORDS: Digital signal processing, Quadrature amplitude modulation, Modulation, Polarization, Modulators, Demodulation, Signal processing, Optical networks, Signal detection, Channel projecting optics
Higher-order multi-level modulation formats are very attractive for achieving the high spectral efficiency and high speed
channels needed to accommodate ultra-high speed client signals on the optical transport network (OTN). In particular,
quadrature amplitude modulation (QAM) is a promising modulation technique to achieve the high spectral efficiency
with PDM. However, required OSNR is increased and transmission distance is restricted as the number of signal point
increase. Moreover, system requirements, such as laser line-width, ADC/DAC resolution, and circuit linearity, become
severe. We recently demonstrated the 3000-km-class long-haul transmission of a single channel 160 Gb/s 16-QAM
signal. We employed three key technologies; optical 16-QAM signal synthesis by superposing two optical QPSK signals,
proposed pilot-less detection scheme with digital PLL-based frequency offset compensator and OSNR improvement by
ultra low-loss fiber and EDFA/distributed Raman amplification. In this paper, we review system configurations for
higher-order QAM, and then describe the single channel transmission performance of 16-QAM.
Visible photoluminescence from multiwalled carbon nanotubes (MWNT) was observed on excitation at 1064 nm. Strong nonlinear behavior of the photoluminescence was shown using power law dependence studies. The nonlinear response in MWNT was further investigated using degenerate four wave mixing. An ultrafast response was observed and the magnitude of the third order optical susceptibility, (chi) , was determined to be in the region of 1.2x10-10 esu. Van Hove singularities in the density of states were identified for the first time in MWNT using optical absorption spectroscopy. Optical transitions between the singularities coincide with the spectral region of the photoluminescence. We propose that a multiphoton absorption process, followed by up conversion luminescence, is responsible for nonlinear photoluminescence in MWNT. Photoluminescence from graphitic particles (GP) was also investigated. This is shown to result mainly from thermal behavior and well-known optical centers. Blackbody radiation was observed in the near infrared region in both materials with MWNT exhibiting lower blackbody temperatures than graphite under the same irradiation conditions.
We report on the lasing action of the graded-index polymer optical fibers containing dyes, such as Rhodamine B, Rhodamine 6G, Perylene Orange, and Pyrromethene 567. These dyes have been incorporated into poly(methyl methacrylate- co-2-hydroxythyl methacrylate). These fibers were transversely pumped at 532 nm with a frequency-doubled Q- switched Nd:YAG laser. Slope efficiency of 24 percent and output of 1.2 mJ were obtained with a Rhodamine 6G-doped fiber. A lifetime of 200,000 pulses at 10 Hz was achieved with a Rhodamine B-doped fiber. GI POF containing a Nd- chelate have also been fabricated. The absorption spectrum of the fiber exhbit3ed several strong bands in the visible and IR regions. We have observed IR fluorescence of the Nd3+ ion of the fiber at room temperature when it was pumped with an Ar+-pumped dye laser at 580 nm. The Judd-Ofelt theory was applied to the absorption spectrum of Nd3+ in polymer to determine the Judd-Ofelt parameters. From the theory, various radiative properties, such as transition probability, branching ratio, and emission cross section for various emission levels, have been determined and reported.
We propose a new ray-space interpolation scheme using an adaptive filter. Unlike the previous works related to view interpolation, which detect disparities, our scheme adopts a simple signal processing method; adaptive filtering to Epipolar Plane Image (EPI). First, the original EPI is up- sampled. Then, for each pixel to be interpolated, the block surrounding the pixel is analyzed and the best filter is selected according to the analysis. The filter set includes various interpolation filters with different directionality. Finally, we apply the filter to up-sampled EPI and generate the intermediate ray-space data. Since our scheme does not need pattern matching, it requires less computation cost than the conventional interpolation schemes, and therefore, it is very fast and suitable for hardware implementation. Experimental results show that the proposed scheme interpolates ray-space data with higher PSNR than other interpolation methods, such as nearest neighbor interpolation, the linear interpolation and block matching interpolation.
In the ultra smoothness polishing of a kind of Al-Mg alloy plate with alumina and colloidal silica abrasives, the influence of the hydrogen exponent of polishing fluids on the removal rate and the smoothness are examined and discussed by polishing in four hydrogen exponent of fluids of pH equals 2.3 (acid), pH equals 7.3 (neutral), pH equals 9.7 (middle alkaline) and pH equals 11.7 (strong alkaline). In case of polishing with alumina abrasives, the acid fluid has better influence on the removal rate and the surface smoothness than the neutral and the alkaline fluid. The removal rate and the smoothness for alumina-polishing in the neutral fluid are extremely small and worse than those before polishing. The best micro-area smoothness obtained by alumina-polishing in the acid fluid is about 13 nm (P-V). In case of polishing with colloidal silica abrasives, the alkaline fluid has better influence on the removal rate but the hydrogen exponent of fluid has little influence on the smoothness. The best micro-area smoothness is about 5 nm (P-V) for silica-polishing but that excluding pits of about 5 nm in depth becomes below 2 nm. In the silica-polishing of pure aluminum plate, the pit is not formed on the polished surface.