We propose and experimentally demonstrate an all-optical broadband wavelength conversion scheme with simultaneous power amplification based on a pump-modulated fiber optic parametric amplifier (FOPA). All-optical tunable wavelength conversion from one to two wavelengths was achieved with ≥13 dB extinction ratio and <2.7-dB power penalty, accompanied by a high (≥37 dB) and flat ( 3 dB variation) FOPA gain spectrum over 47 nm.

We approach nanophotonic computing on the basis of optical near-field interactions between quantum dots. A table lookup, or matrix-vector multiplication, architecture is proposed. As fundamental functionality, a data summation mechanism and digital-to-analog conversion are experimentally demonstrated using CuCl quantum dots. Owing to the diffraction-limit-free nature of nanophotonics, these architectures can achieve ultrahigh density integration compared to conventional bulky optical systems, as well as low power dissipation.

An all-optical phase multiplexing scheme for phase-modulated signals is proposed and experimentally demonstrated using four-wave mixing (FWM) in a highly-nonlinear fiber (HNLF). Two 10-Gb/s π/2-shifted differential phase-shift keying (DPSK) wavelength-division multiplexing (WDM) signals are experimentally demonstrated to be converted and phase-multiplexed into a 20-Gb/s differential quadrature phase-shift keying (DQPSK) signal with non-return-to-zero (NRZ) and return-to-zero (RZ) formats, respectively. Experimental results show that, due to phase-modulation-depth doubling effect and phase multiplexing effect in the FWM process, a DQPSK signal is successfully generated through the proposed all-optical phase multiplexing with improved receiver sensitivity and spectral efficiency.

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 have proposed and demonstrated a novel optical regenerator architecture employing electroabsorption modulators as wavelength converters. The employment of EA modulators is advantageous for high-speed operation and flexibility in the bit-rate for the pulse regeneration. In addition, the EA modulator-wavelength-converter acts also as a photo diode for clock extraction. Compensation of the optical SNR and Q-factor has been demonstrated, even in cascaded noise load. Furthermore, against dispersion loading, we have confirmed that waveform recovery and Q-factor improvement is obtained by midway insertion of the optical regenerator. The proposed architecture will offer a wide-band-electronics-free optical regenerator in multi-tens of gigabit per second WDM networks.

We propose and demonstrate for the first time in our knowledge, an optical switch circuit architecture furnishing with the "Bridge and Switch" function, conforming to ITUT-T Recommendation G. 841 Annex A for optical Add-Drop Multiplexers (ADMs) in WDM four-fiber ring networks. This function enables optical ADMs to revert automatically from the switching state to their idle state just after the recovery of failure, that is indispensable for the extra traffic accommodation to enhance efficiency of the network operation. We have developed the optical ADM nodes employing the proposed optical switch circuit for each wavelength, arrayed-waveguide gratings (AWGs) and Er-doped fiber amplifiers. In the demonstration, transmission characteristics of the cascaded optical ADM nodes without regenerative repeaters have been verified at first. We have confirmed the ring protection and the automatic protection switching (APS) sequence which includes the automatic reversion in the optical ADM nodes with proposed optical switch circuits.

We have proposed and demonstrated a novel optical regenerator architecture employing electroabsorption modulators as wavelength converters. The employment of EA modulators is advantageous for high-speed operation and flexibility in the bit-rate for the pulse regeneration. In addition, the EA modulator-wavelength-converter acts also as a photo diode for clock extraction. Compensation of the optical SNR and Q-factor has been demonstrated, even in cascaded noise load. Furthermore, against dispersion loading, we have confirmed that waveform recovery and Q-factor improvement is obtained by midway insertion of the optical regenerator. The proposed architecture will offer a wide-band-electronics-free optical regenerator in multi-tens of gigabit per second WDM networks.

We propose and demonstrate for the first time in our knowledge, an optical switch circuit architecture furnishing with the "Bridge and Switch" function, conforming to ITUT-T Recommendation G. 841 Annex A for optical Add-Drop Multiplexers (ADMs) in WDM four-fiber ring networks. This function enables optical ADMs to revert automatically from the switching state to their idle state just after the recovery of failure, that is indispensable for the extra traffic accommodation to enhance efficiency of the network operation. oWe have developed the optical ADM nodes employing the proposed optical switch circuit for each wavelength, arrayed-waveguide gratings (AWGs) and Er-doped fiber amplifiers. In the demonstration, transmission characteristics of the cascaded optical ADM nodes without regenerative repeaters have been verified at first. We have confirmed the ring protection and the automatic protection switching (APS) sequence which includes the automatic reversion in the optical ADM nodes with proposed optical switch circuits.

We have investigated the gain and noise figure characteristics of a Nd-doped silica single-mode fiber amplifier (NDFA) at 1.06 µm which is applicable to various systems using a Nd: YAG laser light source at 1.06 µm, such as free-space laser communications, a fiber sensing system, and a lidar system. A fluorescence spectrum observation of the Nd-doped fibers with various co-dopants shows that the Nd-A1 co-doped fiber is suitable for realizing a high-gain amplifier for the 1.06-µm wavelength region. The pump wavelength tolerance at around 0.81 µm , the gain bandwidth and the sufficient value of the Nd concentration and length product for achieving maximum small signal gain are clarified. A noise figure of almost 3 dB and small signal gain of more than 30 dB are attained by 50-mW pump power. The unique four-level system characteristics, even in low pumppower conditions, provide low noise amplification in the NDFA. These gain and noise characteristics are well described by a simple theoretical model. We also demonstrated high-power operation of the NDFA with four pump LD modules adoptinga polarization-multiplexing technique. More than 100-mW signal output power is available for 1-mW signal input power at 200mW launched pump power. These features of the NDFA as a compact, polarization-independent, spatial-beam -distortion-free amplifier, will allow it to replace the solid sate laser in various applications using a Nd: YAG laser light source at 1.06µm.