We report a trial of 100-GS/s optical quantization with 5-bit resolution using soliton self-frequency shift (SSFS) and spectral compression. We confirm that 100-GS/s 5-bit optical quantization is realized to quantize a 5.0-GHz sinusoid electrical signal in simulation. In order to experimentally verify the possibility of 100-GS/s 5-bit optical quantization, we execute 5-bit optical quantization by using two sampled signals with 10-ps intervals.

In label recognition based on optical correlation processing, to completely discriminate a 4-bit target optical code from all types of 4-bit nontarget ones, we propose a novel label recognition method using both optical time-gating and the designed label recognition filter. We experimentally demonstrate that the intensities of correlation signals of 4-bit similar optical codes can be suppressed by the designed label recognition filter and that only the correlation signal of a 4-bit target optical code can be detected by extraction with optical time-gating. The optical time-gating is realized by using organic nonlinear optical crystal: 2-adamantylamino-5-nitropyridine (AANP).

We propose an optical computing architecture called pure optical parall array logic system (P-OPALS) as an instance of sophisticated optical computing system. On the P-OPALS, high density images can be processed in parallel using the optical system with high resolving power. We point out problems on the way to develop the P-OPALS and propose logical foundation of the P-OPALS called single-input optical array logic (S-OAL) as a solution of those problems. Based on the proposed architecture, an experimental system of the P-OPALS is constructed by using three optical techniques: birefringent encoding, selectable discrete correlator, and birefringent decoding. To show processing capability of the P-OPALS, some basic parallel operations are demonstrated. The results obtained indicate that image consisting of 300 100 pixels can be processed in parallel on the experimental P-OPALS. Finally, we estimate potential capability of the P-OPALS.

We numerically and experimentally demonstrate for the first time a novel all-optical quantization technique using dense spectral slicing with a specially designed arrayed waveguide grating for orthogonal frequency division multiplexed signals. By using a mode-locked laser diode with low jitter, the quantization technique can be achieved a high-speed and low-jitter operation. Both numerical and experimental results confirm the feasibility of 10 GSample/s, completely linear 3-bit step quantization for photonic analog to digital conversion. This optical quantization technique will be beneficial for ultra-high-speed optical communication using digital signal processing.

We report a 40-Gb/s and highly accurate intensity limiter with a single Erbium-Doped Fiber Amplifier (EDFA) for low-power-consumption driving intensity limiting. The intensity limiter based on self-phase modulation with an appropriate pre-chirping procedure makes it possible, which provides a highly accurate limiting of less than 0.01 dB. We fed 40-Gb/s signals with 2.69 dB intensity fluctuation and 4.7 dB improvement on the receiver sensitivity was obtained for a bit error rate of 10-9 by using a numerical simulation.

We investigate a quantization error improvement technique using a dual rail configuration for optical quantization. Our proposed optical quantization uses intensity-to-wavelength conversion based on soliton self-frequency shift and spectral compression based on self-phase modulation. However, some unfavorable input peak power regions exist due to stagnations of wavelength shift or distortions of spectral compression. These phenomena could induce a serious quantization error and degrade the effective number of bit (ENOB). In this work, we propose a quantization error improvement technique which can make up for the unfavorable input peak power regions. We experimentally verify the quantization error improvement effect by the proposed technique in 6 bit optical quantization. The estimated ENOB is improved from 5.35 bit to 5.66 bit. In addition, we examine the XPM influence between counter-propagating pulses at high sampling rate. Experimental results and numerical simulation show that the XPM influence is negligible under ∼40 GS/s conditions.

We investigate resolution improvement in optical quantization with keeping high sampling rate performance in optical sampling. Since our optical quantization approach uses power-to-wavelength conversion based on soliton self-frequency shift, a spectral compression can improve resolution in exchange for sampling rate degradation. In this work, we propose a different approach for resolution improvement by parallel use of dispersion devices so as to avoid sampling rate degradation. Additional use of different dispersion devices can assist the wavelength separation ability of an original dispersion device. We demonstrate the principle of resolution improvement in 3 bit optical quantization. Simulation results based on experimental evaluation of 3 bit optical quantization system shows 4 bit optical quantization is achieved by parallel use of dispersion devices in 3 bit optical quantization system. The maximum differential non-linearity (DNL) and integral non-linearity (INL) are 0.49 least significant bit (LSB) and 0.50 LSB, respectively. The effective number of bits (ENOB) estimated to 3.62 bit.

A high degree of freedom in spectral domain allows us to accommodate additional optical signal processing for wavelength division multiplexing in photonic analog-to-digital conversion. We experimentally verified a spectral compression to save a necessary bandwidth for soliton self-frequency shift based optical quantization through the cascade of the four-wave mixing based and the sum-frequency generation based spectral compression. This approach can realize 0.03 nm individual bandwidth correspond to save up to more than 85 percent of bandwidth for 7-bit optical quantization in C-band.

We propose and demonstrate the all-optical analog-to-digital conversion (ADC) using optical delay line encoders. Experimental results show that input analog signals are successfully converted into 3-bit digital signals at a bit rate of 40 Gb/s.

Performance analysis of ultra-fast all-optical analog-to-digital converter using optical multiple-level thresholding module based on self-frequency shift in fiber is described. In analog-to-digital conversion, the purposes of optical sampling and optical quantization are in the possibility of the speed-up of sampling and quantization processes using various ultra-fast nonlinear phenomena depending on an intensity of a light. The result of analysis indicates that the number of achievable quantized levels of the proposed approach is in the increasing tendency with an increase in the peak power of an input pulse.