This paper reports recent advances in photonic functional devices based on silica planar lightwave circuit technology for advanced optical networks. After briefly summarizing the progress on circuits, this work describes dynamic devices designed to compensate for unwanted fiber characteristics with respect to high-speed wavelength division multiplexing transmissions, mainly focusing on a tunable chromatic dispersion compensator. The paper then describes optical signal processing devices, namely a spectrum synthesis device, an optical encoder/decoder for time-spreading/wavelength-hopping optical code division multiple access, and a label processor for a phase modulated signal.
This paper reports recent advances in photonic functional devices. These devices are being developed for advanced optical networks and are fabricated by using planar lightwave circuit technology. After briefly summarizing the fabrication, properties, and progress of silica based planar lightwave circuits, this work describes lattice-form dynamic devices designed to compensate for unwanted fiber characteristics with respect to high-speed wavelength division multiplexing transmissions. These dynamic devices include adaptive chromatic dispersion, polarization-mode dispersion, and gain non-uniformity compensators. The paper then describes optical signal processing devices for communications use, namely an optical label recognition device, an optical encoder/decoder for time-spreading/wavelength-hopping code division multiple access, and a spectrum synthesis device.
We analyze the performance of InP/GaAs fused 1.55 micrometers vertical-cavity lasers (VCLs) under analog modulation. Our VCLs employ a strain-compensated InGaAsP/InP multi-quantum well (MQW) active region sandwiched between two AlGaAs/GaAs distributed Bragg reflectors. The first AlGaAs layer of the p-doped top mirror is laterally oxidized for optical and electrical confinement. These devices exhibit the lowest threshold current as well as the highest temperature of continuous-wave operation of any electrically pumped long- wavelength VCL. Two different device designs are investigated and compared. Reduction of the MQW barrier strain and enhancement of the optical index guiding by the oxide layer lead to an improvement of VCL performance. However, parasitic effects limit the modulation bandwidth. Higher order harmonic distortion is measured and simulated using a rate equation model. The model includes a non-linear gain function, gain compression, spontaneous emission and Auger recombination as well as carrier density dependent absorption in the quantum wells which reduces the differential gain. The good agreement between measurement and simulation indicates that electron-photon interaction within the quantum wells dominates the non-linear distortion. Multiple higher order response peaks are measured and reproduced by the model.
In this paper, we report a novel configuration of micro optic gyro (MOG), which is monolithically integrated on silica Planar Lightwave Circuit (PLC) with countermeasures for noise factors. Optical ring-resonator gyros suffer mainly form polarization fluctuation induced noise and backscattering induced noise. We adopt a stress applying amorphus silicon film as the countermeasure for the former, and binary phase shift keying (b-PSK) as the one for the latter. However, to apply b-PSK, thermo-optic (TO) phase modulation is the only one scheme available in silica waveguide, whose bandwidth is limited to approximately 1 KHz. To utilize the narrow bandwidth of the TO modulator effectively, we propose an electrical signal processing scheme and frequency compensating modulation waveform. We demonstrate the suppression of the backscattering induced noise as 7.6dB. Additionally the gyro output is observed with applying an equivalent rotation.
A test program has been conducted with a view to defining methods for reducing the drift of optical passive ring-resonator gyros (OPRG). Attention is given to such noise sources and noise-reduction techniques as Rayleigh backscattering, polarization fluctuation, and fiber-resonator optical Kerr effect. A novel, partial digital feedback scheme is defined for preventing the OPRG from lapsing into large drift, due to thermal expansion of the resonator.