Kuninori Hattori

Low loss and high extinction ratio strictly nonblocking 16/spl times/16 thermooptic matrix switch on 6-in wafer using silica-based planar lightwave circuit technology

We describe a silica-based 16/spl times/16 strictly nonblocking thermooptic matrix switch with a low loss and a high extinction ratio. This matrix switch, which employs a double Mach-Zehnder interferometer (MZI) switching unit and a matrix arrangement to reduce the total waveguide length, is fabricated with 0.75% refractive index difference waveguides on a 6-in silicon wafer using silica-based planar lightwave circuit (PLC) technology. We obtained an average insertion loss of 6.6 dB and an average extinction ratio of 53 dB in the worst polarization case. The operating wavelength bandwidth completely covers the gain band of practical erbium-doped fiber amplifiers (EDFAs). The total power consumption needed for operation is reduced to 17 W by employing a phase-trimming technique which eliminates the phase-error in the interferometer switching unit.

Low-loss and high-extinction-ratio silica-based strictly nonblocking 16/spl times/16 thermooptic matrix switch

A low-loss and high-extinction-ratio silica-based 16/spl times/16 thermooptic matrix switch is demonstrated. The switch, which employs a double Mach-Zehnder interferometer switching unit and a matrix arrangement which reduces the total waveguide length, is fabricated with 0.75% refractive index difference waveguides on a 6-in silicon wafer. The average insertion loss and the average extinction ratio are 6.6 and 55 dB, respectively. The total power consumption is 17 W.

High-extinction ratio and low-loss silica-based 8/spl times/8 strictly nonblocking thermooptic matrix switch

This paper describes a silica-based 8/spl times/8 strictly nonblocking thermooptic matrix switch with a high-extinction ratio and low loss. We realized this matrix switch by using a configuration which combines a double Mach-Zehnder interferometer (MZI) switching unit and an N/spl times/N matrix arrangement thus reducing the total waveguide length. The 8/spl times/8 matrix switch was fabricated on a 4-in wafer using planar lightwave circuit technology. We obtained an average extinction ratio of 60.3 dB and an average insertion loss of 5.1 dB. The operating wavelength bandwidth completely covers the gain band of practical erbium-doped fiber amplifiers (EDFAs).

Dispersion slope equalizer for dispersion shifted fiber using a lattice-form programmable optical filter on a planar lightwave circuit

This paper reports an integrated-optic dispersion slope (third-order dispersion) equalizer for dispersion shifted fiber which employs a lattice-form programmable optical filter on a planar lightwave circuit (PLC). This dispersion slope equalizer consists of nine symmetrical interferometers interleaved with eight asymmetrical interferometers. The performance of the equalizer is evaluated numerically. We confirm experimentally that this equalizer is effective in reducing the pulse waveform deterioration caused by the dispersion slope. In addition, the equalizer improves the power penalty of a 200-Gb/s, 100-km, time-division multiplexed optical transmission experiment.

Erbium-doped silica-based planar-waveguide amplifier integrated with a 980/1530-nm WDM coupler

Erbium-doped glass waveguides are expected to be used as active elements in integrated-optical devices for optical-communication systems.1 Planar-waveguide optical amplifiers have been realized with straight and with curved erbium-doped glass waveguides.2,3 However, there have been no reports to date on sophisticated planar-waveguide amplifiers integrated with a pump/signal-light multiplexing circuit. Here, we describe what we believe to be the first integrated silica-based planar-waveguide amplifier on a silicon substrate with a 980/1530-nm wavelength-division-multiplexing (WDM) directional coupler lor multiplexing the pump and signal lights.

Optical amplification in Er3+‐doped P2O5–SiO2 planar waveguides

The small signal gain of Er3+‐doped P2O5–SiO2 planar waveguides is described with a homogeneous upconversion model. The homogeneous upconversion process accurately describes the absorption saturation at a wavelength of 0.98 μm. Interpretation of the absorption saturation provides homogeneous upconversion coefficients of 4×10−15 cm3 s−1 for a 0.54 wt % Er3+‐doped 14.6 wt % P2O5 codoped silica waveguide and 6×10−18 cm3 s−1 for a 0.46 wt % Er3+‐doped 21.6 wt % P2O5 codoped silica waveguide. The upconversion process occurs in the Er3+ ion rich phase in the P2O5–SiO2 core glass. A calculation that includes the homogeneous upconversion process proves that the gain can be enhanced by codoping the planar waveguide with P2O5. A gain of 20 dB is calculated with an Er3+ ion concentration of 0.4–0.7 wt % and a waveguide length of 40 cm when the pump power is 100 mW and 20 wt % P2O5 codoped Er3+‐doped silica‐based planar waveguides are used.

Neodymium-doped silica-based planar waveguide lasers

Fabrication and lasing characteristics of Nd-doped P/sub 2/O/sub 5/-SiO/sub 2/ core planar waveguide lasers are described. CW oscillation at a wavelength of 1052.5 nm was successfully demonstrated in 0.2 wt%-Nd-doped silica-based planar waveguides fabricated on a silicon substrate by flame hydrolysis deposition and reactive ion etching. The lasing threshold and slope efficiency were optimized in an 8-/spl mu/m-wide waveguide, in which a lasing threshold pump power of 26 mW and a slope efficiency of 2.0% were obtained for 805-nm pumping. The measured lasing characteristics agreed with theoretical characteristics calculated by employing finite-element waveguide analysis, indicating that the waveguide structure was well controlled by the developed waveguide fabrication technique. The possible lasing characteristics of the waveguide lasers are discussed based on this agreement. The attenuation and emission properties of the waveguides are also described. >

Bidirectional transmission to suppress interwavelength-band nonlinear interactions in ultrawide-band WDM transmission systems

Interwavelength-band nonlinear interactions are investigated as possible causes of performance degradation in ultrawide band wavelength-division-multiplexed transmission. These interactions can severely limit the performance of transmission over dispersion-shifted fibers (DSFs) and nonzero DSFs. Bidirectional transmission is found to be effective in suppressing interwavelength-band nonlinear interactions.

High-extinction ratio and low-loss silica-based 8/spl times/8 thermooptic matrix switch

A high-extinction ratio and low-loss silica-based 8/spl times/8 thermooptic matrix switch is demonstrated. The 8/spl times/8 matrix switch is realized by using a double Mach-Zehnder interferometer switching unit and a matrix arrangement which reduces the total waveguide length. The average extinction ratio and the average insertion loss are 60.3 and 5.2 dB, respectively.

Interwavelength-band nonlinear interactions and their suppression in multiwavelength-band WDM transmission systems

We describe the effects of interwavelength-band nonlinear interactions, such as nondegenerate four-wave mixing, stimulated Raman scattering, and cross-phase modulation in multiwavelength-band WDM transmission systems. Through both numerical analysis and transmission experiments, these interactions are shown to cause serious degradation, especially when the walk-off between the utilized wavelength bands is small. Focusing on suppressing both these interwavelength-band nonlinear interactions and traditional intrawavelength-band nonlinear interactions, we present the guidelines for designing ultra wide-band WDM transmission systems over various types of fibers. The guidelines include band-by band bidirectional transmission, which offers large walk-off and minimizes the degradation caused by interwavelength-band nonlinear interactions. Finally, several dual-wavelength-band transmissions over dispersion-shifted fibers and standard single-mode fibers are demonstrated according to the guidelines.