Takashi Saida

Distributed fiber-optic stress sensor by synthesis of the optical coherence function

A distributed fiber-optic stress sensor by synthesis of the optical coherence function is proposed. This system can obtain polarization coupling distribution in a polarization maintaining fiber due to lateral stress, using neither mechanical moving parts nor further calculations. In experiments, the spatial resolution of about 9 m and the measurable range of about 1040 m are demonstrated.

General formula describing drift of interferometer fiber-optic gyro due to Faraday effect: reduction of the drift in twin-depo-I-FOG

The drift of an interferometric fiber-optic gyro (I-FOG) by the magnetic field through the Faraday effect is generally formulated. By the derived formula, the drift reduction mechanism in the interferometric fiber-optic gyro using ordinary single-mode fiber as a sensing coil and two depolarizers (twin-depo-I-FOG) is clarified, as well as that in the interferometric fiber-optic gyro using polarization maintaining fiber (PM-I-FOG). Degradation factors in the practical twin-depo-I-FOG are evaluated by using the derived equation, and methods for further drift reduction are discussed.

New Optical Waveguide Design Based on Wavefront Matching Method

We have studied the wavefront matching (WFM) method, which synthesizes optimum waveguide patterns from the desired characteristics, and demonstrated its feasibility. In this paper, we expand this method to create optimum waveguide shapes with low-loss and low-wavelength dependence in waveguide lenses, Y-branches, and waveguide crossings. We describe the design procedures for each waveguide element and report the experimental results as proof of concept. The measured results agree well with our design requirements, and the waveguide patterns designed by the WFM method exhibit better characteristics than the reference patterns.

Planar lightwave circuit polarization mode dispersion compensator

We fabricated an integrated-type optical PMD compensator on a silica-based planar lightwave circuit, where an endless polarization controller and a polarization-dependent delay line are installed. We confirmed its operational principle in a 43-Gbps transmission system.In this letter, we fabricated an integrated polarization-mode dispersion compensator on a silica-based planar lightwave circuit that incorporated an endless polarization controller and a fixed polarization dependent delay line. The compensator consisted of polarization beam splitters, thermooptic phase shifters, tunable couplers, and polarization converters. We experimentally confirmed its operation at a data rate of 43 Gb/s.

Silica-based, compact and variable-optical-attenuator integrated coherent receiver with stable optoelectronic coupling system

We demonstrate a compact and variable-optical-attenuator (VOA) integrated coherent receiver with a silica-based planar lightwave circuit (PLC). To realize the compact receiver, we integrate a VOA in a single PLC chip with polarization beam splitters and optical 90-degree hybrids, and employ a stable optoelectronic coupling system consisting of micro lens arrays and photodiode (PD) subcarriers with high-speed right-angled signal lines. We integrate a VOA and a coherent receiver in a 27x40x6 mm package, and successfully demodulate a 128-Gbit/s polarization division multiplexed (PDM) quadrature phase shift keying (QPSK) signal with a VOA-assisted wide dynamic range of more than 30 dB.

Temperature insensitive and ultra wideband silica-based dual polarization optical hybrid for coherent receiver with highly symmetrical interferometer design.

We designed temperature-insensitive dual-polarization optical hybrids for the coherent receivers, and firstly demonstrated temperature-insensitive performance with a polarization extinction ratio over 25 dB and phase errors within 3 degrees over fully C-and L-bands.

Low-Loss Y-Branch Waveguides Designed by Wavefront Matching Method

In this paper, we describe the procedure for designing low-loss Y-branch waveguides by the wavefront matching (WFM) method, and report experimental results as proof of concept. The designed Y-branches were fabricated using silica-based planar lightwave circuit (PLC) technology. A Y-branch fabricated with a 0.45%-Delta waveguide exhibited a low excess loss of less than 0.2 dB over a wide wavelength range of 1250 to 1650 nm. In addition, we demonstrate that the WFM-designed Y-branches enable us to provide compact 1 times 32 splitters with an average insertion loss of 16.0 dB at a wavelength of 1550 nm. In addition, we present some experimental results obtained using samples with different Delta values, and show that our design method is more efficient for a higher Delta waveguide suitable for functional PLC devices.

High-spatial resolution reflectometry by synthesis of optical coherence function for measuring reflectivity distribution at a long distance

A high-spatial resolution reflectometry by synthesis of the optical coherence function is proposed for testing optical devices and circuits at the far end of optical subscriber networks. The system can measure the reflectivity distribution at a long distance without performance degradation resulting from the phase fluctuation in a long-length optical fiber. Reflectivity distribution at a distance of 5 km is measured successfully with the spatial resolution of 6 cm.

86-Gbit/s differential quadrature phase-shift-keying modulator using hybrid assembly technique with planar lightwave circuit and LiNbO3 devices

We developed an 86-Gbit/s DQPSK modulator by using four arrayed optical phase modulators with an LN waveguide and two 1times4 coupler PLCs by adopting the WFM technique. This modulator exhibited excellent DQPSK modulation performance

Planar lightwave circuit polarization-mode dispersion compensator

In this letter, we fabricated an integrated polarization-mode dispersion compensator on a silica-based planar lightwave circuit that incorporated an endless polarization controller and a fixed polarization dependent delay line. The compensator consisted of polarization beam splitters, thermooptic phase shifters, tunable couplers, and polarization converters. We experimentally confirmed its operation at a data rate of 43 Gb/s.