Multiple optical code-label processing using multi-wavelength frequency comb generator and multi-port optical spectrum synthesizer.

In optical packet switching (OPS) and optical code division multiple access (OCDMA) systems, label generation and processing are key technologies. Recently, several label processors have been proposed and demonstrated. However, in order to recognize N different labels, N separate devices are required.

Asymptotic formalism for ultraflat optical frequency comb generation using a Mach-Zehnder modulator.

We theoretically prove that a conventional Mach-Zehnder modulator can generate an optical frequency comb with excellent spectral flatness. The modulator is asymmetrically dual driven by large amplitude sinusoidal signals with different amplitudes. The driving condition to obtain spectral flatness is analytically derived and optimized, yielding a simple formula.

High-speed optical DQPSK and FSK modulation using integrated Mach-Zehnder interferometers.

We investigated an integrated optical modulator consisting of two Mach-Zehnder interferometers. The modulator can generate optical signals in various types of modulation formats, which have advantages for long-haul transmission, optical labeling, etc. By using a fabricated versatile optical modulator having traveling-wave electrodes designed for high-speed signals, we demonstrated generation of optical 40Gb/s frequency-shift-keying signals, which can be demodulated by an optical filter.

Optoelectronic oscillator using a LiNbO3 phase modulator for self-oscillating frequency comb generation.

Optical frequency comb generation by using a novel optoelectronic oscillator (OEO) is proposed and demonstrated with the emphasis placed on self-oscillating operation. In the OEO, a wideband LiNbO3 phase modulator is driven with a large-amplitude radio-frequency (RF) feedback signal to generate a deeply phase-modulated light wave; accordingly, an optical frequency comb with a bandwidth greater than the RF signal is generated by self-oscillation. Although it generates multifrequency components, the OEO exhibits characteristics of a single-mode oscillator.

All-optical modulation format conversion from frequency-shift-keying to phase-shift-keying.

We have realized a novel optical modulation format conversion using double-sideband suppressed-carrier modulation. An optical wideband frequency-shift-keying (FSK) signal, generated by an external FSK modulator, can be directly converted into an optical phase-shift-keying (PSK) signal, where the FSK signal having two spectral components was fed to an optical intensity modulator followed by an optical bandpass filter. Optical frequency of the FSK signal was mapped into optical phase of the bandpass filter output whose phase deviation depends on a chirp of the FSK signal.

Optical minimum-shift keying with external modulation scheme.

We propose an optical initial phase control technique for external modulation in the format of minimum-shift keying (MSK). In this scheme, the optical phase discontinuities inherent to external frequencyshift- keying (FSK) modulation are compensated by use of an initial phase controller in conjunction with a FSK modulator. We present the principle of the control method and then numerically and experimentally prove that the signal has a modulation spectrum more compact than that of conventional binary phase-shift keying.