A. Himeno

Phase‐noise and shot‐noise limited operations of low coherence optical time domain reflectometry

This letter shows theoretically and experimentally that Fresnel end reflection of the waveguide under test degrades the sensitivity of low coherence optical time domain reflectometry (OTDR). Optical mixing of end reflection and reference light in the OTDR produces the phase noise in proportion to end reflectivity. With the balanced detection technique, the excess photon noise is subdued and the phase noise becomes the dominant source of sensitivity degradation. At 3.2% end reflection and 300 μA mean photocurrent, the noise floor due to the phase noise is −138 dB/Hz. By reducing the fiber end reflection with matching oil, a shot‐noise limited sensitivity of −140 dB at a 3 Hz bandwidth has been demonstrated at submillimeter resolution.

Very low insertion loss arrayed-waveguide grating with vertically tapered waveguides

We propose and demonstrate a very low insertion loss silica-based arrayed-waveguide grating (AWG) achieved using a novel structure, which has vertically tapered waveguides between arrayed-waveguides to reduce the slab-to-arrayed-waveguide transition loss. A spot-size converter is also incorporated in the AWG to reduce the fiber-to-waveguide coupling loss. The structure can be formed by a process involving the conventional photolithography and reactive ion etching. The structure provided a loss reduction of 1.5 dB. Moreover, we have successfully obtained a minimum insertion loss of 0.75 dB with a crosstalk of -40 dB and polarization-independent operation.

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.

Loss measurement and analysis of high-silica reflection bending optical waveguides

Bending loss of high-silica single-mode bending optical waveguides using a waveguide side-wall as a reflecting facet is described theoretically and experimentally as a function of the bending angle. Two types of bending waveguides, which have the reflecting facet exposed to the air coated with a metal film, are treated. The causes of bending loss are discussed in terms of los due to the Goos-Hanchen effect and the perpendicularity and roughness of the reflecting facet. >

Elimination of polarization sensitivity in silica-based wavelength division multiplexer using a polyimide half waveplate

This paper proposes a low-loss technique for eliminating polarization sensitivity in a silica-based planar lightwave circuit (PLC) which uses a polarization mode converter formed at the center of the circuit. This converter consists of a waveguide gap housing a polyimide half waveplate. The excess loss of the converter was drastically reduced to 0.26 dB with a /spl Delta/=0.75% waveguide by employing an 18 /spl mu/m-wide waveguide gap and a 14.5 /spl mu/m-thick polyimide half waveplate. A polarization mode conversion crosstalk of -37 dB was achieved at 1.55 /spl mu/m. Using this converter, we successfully eliminated the polarization sensitivity in some silica-based PLC-type wavelength division multiplexers. The converter is also insensitive to temperature and offers long term stability.

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.

New structure of silica-based planar lightwave circuits for low-power thermooptic switch and its application to 8 /spl times/ 8 optical matrix switch

We propose a novel structure that reduces the switching power of a silica-based thermooptic switch (TOSW). The structure consists of silicon trenches and heat insulating grooves, which are formed beneath and beside the arms of a Mach-Zehnder interferometer, respectively. We optimize the structure using the differential-element method (DEM) and fabricate a 2 /spl times/ 2 TOSW with a switching power of only 90 mW, namely, 75% less than that of a conventional TOSW. We also obtain an insertion loss of about 1 dB and an extinction ratio of over 30 dB with a response time from 0% to 90% of 4.9 ms. We then use the structure to fabricate an 8 /spl times/ 8 matrix switch and confirm a total power consumption of 1.4 W with an average insertion loss of 7.4 dB and an extinction ratio of 50.4 dB for 64 possible optical paths.

Low-power consumption silica-based 2 x 2 thermooptic switch using trenched silicon substrate

We propose a silica-based 2/spl times/2 thermooptic switch using heat insulating grooves and trenches on a Si substrate to reduce electric power consumption. The switching power of a fabricated switch was successfully reduced to 135 mW, less than 1/3 that of a conventional switch. No detrimental effect on optical characteristics was observed: we obtained the insertion loss of 1 dB, the extinction ratio of better than 30 dB and no polarization dependency.