Takui Uematsu

Design of a Compact Two-Mode Multi/Demultiplexer Consisting of Multimode Interference Waveguides and a Wavelength-Insensitive Phase Shifter for Mode-Division Multiplexing Transmission

A compact two-mode (de)multiplexer (TM-MUX) based on Si nanowire for mode-division multiplexing is designed. The TM-MUX is composed of two multimode interference (MMI) waveguides and a butterfly-shape tapered phase shifter between two MMI waveguides. Numerical simulations show that the designed device is compact compared with conventional-mode (de)multiplexer and operates as a TM-MUX in the whole C-band. In addition, we show that the designed TM-MUX has relatively good fabrication tolerance.

PLC-based LP 11 mode rotator for mode-division multiplexing transmission

A PLC-based LP11 mode rotator is proposed. The proposed mode rotator is composed of a waveguide with a trench that provides asymmetry of the waveguide. Numerical simulations show that converting LP11a (LP11b) mode to LP11b (LP11a) mode can be achieved with high conversion efficiency (more than 90%) and little polarization dependence over a wide wavelength range from 1450 nm to 1650 nm. In addition, we fabricate the proposed LP11 mode rotator using silica-based PLC. It is confirmed that the fabricated mode rotator can convert LP11a mode to LP11b mode over a wide wavelength range.

PLC-Based Four-Mode Multi/Demultiplexer With LP 11 Mode Rotator on One Chip

We propose a PLC-based mode multi/demultiplexer (MUX/DEMUX) for mode-division multiplexing. We show numerically that the PLC-based mode MUX/DEMUX with a uniform height on one chip can multi/demultiplex four modes (LP₀₁, LP₁₁a, LP₁₁b, and LP₂₁a) by using our proposed LP₁₁ mode rotator and a parallel waveguide. We successfully multi/demultiplex the four modes and achieve a relatively low-wavelength dependence over the C-band by using our fabricated four-mode MUX/DEMUX.

Multicore fibre-based mode multiplexer/demultiplexer for three-mode operation of LP 01 , LP 11a , and LP 11b

A mode multiplexer/demultiplexer with a fused-fibre fan-in/fan-out device for three-mode operation of LP₀₁, LP_11a, and LP_11b is demonstrated using a partially elongated multi-core fibre. A fabricated mode multiplexer/demultiplexer exhibited a coupling efficiency greater than 79% over the C band.

Ultra-Broadband Silicon-Wire Polarization Beam Combiner/Splitter Based on a Wavelength Insensitive Coupler With a Point-Symmetrical Configuration

An ultrabroadband silicon wire polarization beam combiner/splitter (PBCS) based on a wavelength-insensitive coupler is proposed. The proposed PBCS consists of three identical directional couplers and two identical delay lines. We design the PBCS using the 3-D finite element method. Numerical simulations show that the proposed PBCS can achieve the transmittance of more than 90% over a wide wavelength range from 1450 to 1650 nm for both TE and TM polarized modes.

Optical Cable Changeover Tool With Light Injection and Detection Technology

We propose a switching equipment that employs a bent fiber and its application for changing optical cables in an access network. This equipment reduces the length of the interruption in the transmission between an optical line terminal and an optical network unit during construction work. We designed the equipment with communication light injection and detection technology.

Multicore fiber-based mode multiplexer/demultiplexer

A multicore fiber (MCF)-based mode multiplexer/demultiplexer (MUX/DEMUX) that can overcome the alignment issue of the fiber-based mode MUX/DEMUX is proposed. Design concept and fabrication results of the MCF-based mode MUX/DEMUX for two-spatial-mode operation (LP01 and LP11) (2M-MUX/DEMUX) and for three-spatial-mode operation (LP01, LP11a, and LP11b) (3M-MUX/DEMUX) are presented. The fabricated 2M-MUX/DEMUXes for C-band or L-band, using the same MCF with different elongation ratios demonstrate a coupling efficiency of greater than 90% over each band. Finally, a 3M-MUX/DEMUX with a fan-in/fan-out device is presented. The selective excitation of LP01, LP11a, and LP11b modes depending on input ports is experimentally demonstrated.

High-efficiency light injection and extraction using fiber bending

We achieve a temporary optical coupler that injects/extracts light into/from a fiber with high efficiency by using fiber bending. We demonstrate experimentally that extraction efficiency is improved by using a double-clad fiber.

Design of a Temporary Optical Coupler Using Fiber Bending for Traffic Monitoring

We design a temporary optical coupler that extracts 1.25-Gbps optical signals for traffic monitoring. The temporary optical coupler employs a fiber bending technique that uses a receiving fiber to receive leaked signal light from a bent fiber. We optimize the bending condition and the receiving fiber to obtain a high extraction efficiency while keeping the bending loss below 2 dB. We also measure the bit error rates for the 1.25-Gbps signals and reveal that our temporary optical coupler extracts the 1.25-Gbps optical signals without any deterioration in signal quality. Finally, we confirm experimentally that we achieved traffic monitoring using a traffic monitoring system and our temporary optical coupler in a fiber-to-the-home access network system based on a gigabit Ethernet passive optical network.

Four-mode PLC-based mode multi/demultiplexer with LP 11 mode rotator on one chip for MDM transmission

We demonstrated a four-mode multi/demultiplexer using an LP₁₁ mode rotator and a parallel waveguide with a uniform height on one chip for mode division multiplexing transmission. Four-mode (LP₀₁, LP_11a, LP_11b, and LP_21a mode) multi/demultiplexing was successfully achieved with a fabricated PLC.