Koji Omichi

Warm-white light-emitting diode with yellowish orange SiAlON ceramic phosphor

A warm-white light-emitting diode (LED) without blending of different kinds of phosphors is demonstrated. An approach that consists of a blue LED chip and a wavelength-conversion phosphor is carried out. The phosphor is a newly developed yellowish orange CaEuSiAlON ceramic phosphor with high efficiency. The CIE1931 chromaticity coordinates (x, y) are (0.458, 0.414), the color temperature is 2750 K, and the luminous efficacy of this LED is 25.9 lm/W at room temperature and with a forward-bias current of 20 mA. The chromaticity of the assembled LED is more thermally stable than that of a LED with a conventional oxide phosphor (YAG:Ce) because of the better thermal stability of the oxynitride phosphor.

40G-OCDMA-PON System With an Asymmetric Structure Using a Single Multi-Port and Sampled SSFBG Encoder/Decoders

In the hybrid optical code division multiple access (OCDMA) architectures using different types of optical encoder/decoder (E/Ds) between an optical line terminal and optical network units, a hybrid 40G-OCDMA-PON with a single multi-port and super-structured fiber Bragg grating (SSFBG) E/Ds is studied as a candidate system beyond next-generation PON stage 2 (NG-PON2). In this paper, we have developed uniformed and sampled SSFBG E/Ds with different refractive index profiles and have compared their code performances in a hybrid 40G-OCDMA-PON system. The experimental results show that the sampled profile improves the code dependent performances presented in many OCDMA systems. We have also demonstrated a full-duplex 4-user × 40 Gb/s hybrid OCDMA-PON system by applying the sampled SSFBG E/Ds. An asynchronous full-duplex 50 km transmission with a total capacity of 160 Gb/s (4-user × 40 Gb/s) has been achieved for the first time. Furthermore, we focus on major requirements in NG-PON2 and discuss several issues to introduce the hybrid 40G-OCDMA-PON for optical access networks.

Measurement of distributed strain and load identification using 1500 mm gauge length FBG and optical frequency domain reflectometry

High spatial resolution and sensitivity are required in distributed strain measurements for structural health monitoring. We have developed a distributed strain sensing technique with long gauge FBG sensors, which enables to measure strain at an arbitrary position along the FBG sensors with the high spatial resolution less than 1 mm based on optical frequency domain reflectometry (OFDR). In this paper this technique with a 1500 mm gauge length FBG was applied to monitoring strain distributions of a simply supported beam subjected to bending loads. The agreement between the measured strain and the theoretical one is excellent. Also we succeeded to identify the applied load by the inverse analysis from the measured strain distribution data, and confirmed the validity of these methods.

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.

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.

Multi-core to 7 single-core-fibers fan-out device with multi-core fiber pigtail connector

Multi-core to 7 single-core-fibers fan-out device with multi-core fiber pigtail connector is demonstrated to apply various types of multi-core fiber based sensor. Fused taper type fan-out device and SC type multi-core fiber connector are separately fabricated on each process. The fan-out device and the pigtail multi-core fiber are spliced each other by a specialty fiber fusion splicer. Comparatively low average insertion loss of 0.95 dB and sufficiently low reflectivity of less than -60 dB are achieved.

Superstructured FBG based optical encoder/decoder for highly-confidential 40 Gbps telecommunication network

40 Gbps optical encoding/decoding is demonstrated utilizing 8-level phase codes, 8 grating chips and 2.6 mm long superstructured fiber Bragg grating (SSFBG). Novel refractive index profile is applied to the SSFBG to obtain highlyrecognizable performance of encoding signal and highly-confidential decoding signal. Time-spreading optical codes are clearly observed from the encoding signals, and over 13 dB power contrast ratio is confirmed from the decoding signals.

Temperature monitoring of superconducting wire for quench detection

Multipoint temperature measurement of the superconducting wire was demonstrated to detect quench behavior utilizing a multiplexed fiber Bragg gratings sensor. The sensor was directly attached on the wire to measure actual wire temperature during the quenching. Quench propagation was successfully detected by measuring delay time of temperature increase on each grating.

Biaxial Measurement of Optical Frequency Domain Reflectometry Using Polarization Maintaining Fiber Bragg Grating

We demonstrated the optical frequency domain reflectometry (OFDR) measurement system with all polarization maintaining fiber including fiber Bragg grating (FBG). We succeeded to obtain the slow and fast axial Bragg reflection spectra individually. We proposed the novel method to compensate the measured position miss matching between slow and fast axial Bragg reflection spectra, and confirmed the validity of the method.

Cost-effective, asynchronous 4 × 40Gbps full-duplex OCDMA demonstrator using apodized SSFBGs and a multi-port encoder/decoder

Cost-effective, asynchronous 4 × 40Gbps full-duplex DPSK-OCDMA PON using 8-level phase-shifted, 320 Gchip/s apodized SSFBG en/decoders at each ONU and a single multi-port en/decoder at OLT is experimentally demonstrated for the first time.