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Papers by Toshitaka Torikai

Conference Proceedings LEOS'96 9th Annual Meeting IEEE Lasers and Electro-Optics Society

ABSTRACT A high efficiency of 0.4 W/A at 85°C, the highest ever reported for InGaAsP MQW-LDs enti... more ABSTRACT A high efficiency of 0.4 W/A at 85°C, the highest ever reported for InGaAsP MQW-LDs entirely grown by MOVPE, was realized. The efficiency change was a low 2.5 dB over -40 to +85°C for a surface-mount module

Optical Fiber Communication, 1988

Recently, multigigabit long-span optical fiber transmission experiments have been reported(1-4) f... more Recently, multigigabit long-span optical fiber transmission experiments have been reported(1-4) following investigations on feasibility for future trunk line systems. An 8Gb/s-68.3km transmission at 1.53μm wavelength, has been carried out using an external modulator and a normal single-mode fiber1). However, high-speed transmission systems using directly modulated LDs and dispersion shifted (DS) fibers are also attractive. The reason is that higher fiber input power for the transmitter and small dispersion in DS fibers provide longer span transmission at 1.55μm wavelength.

Electronics Letters, 1989

Electronics Letters, 1995

ABSTRACT An extremely low 0.4 mA threshold current has been achieved for novel current-blocking 1... more ABSTRACT An extremely low 0.4 mA threshold current has been achieved for novel current-blocking 1.3 μm strained MQW laser diodes. These devices are grown by MOVPE using tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) precursors. The lowest threshold currents of 0.4 and 3.00 mA were obtained at 20 and 85°C, respectively, for a 150 μm-long 95%/98%-coated device

Technical Digest of the Eighteenth Microoptics Conference, 2013

We developed a cost effective and precise ballpoint pen termination designed for graded index pol... more We developed a cost effective and precise ballpoint pen termination designed for graded index polymer optical fiber, which realized high coupling efficiency despite rough connection. We invented a thin, lightweight, and flexible 120 Gb/s optical cable with compact interface, and demonstrated 8K ultra high definition video data transmission.

Summary: Well-defined wavelength distributed feedback laser diodes (DFB-LDs) are required in WDM ... more Summary: Well-defined wavelength distributed feedback laser diodes (DFB-LDs) are required in WDM network systems. Since the EDFA gain bands have been expanded, even more wavelengths are needed for large-capacity dense-WDM transmission systems. A precisely pitch-...

Semiconductor Lasers III, 1998

ABSTRACT This paper clarifies superior external optical feedback resistant characteristics in par... more ABSTRACT This paper clarifies superior external optical feedback resistant characteristics in partially-corrugated-waveguide laser diodes (PC-LDs), compared to conventional distributed feedback laser diodes (DFB-LDs). Based on a novel large single dynamic analysis by using the van der Pol equations in single-mode laser diodes (LDs), it is found that the external optical feedback resistance in single-mode LDs is dominated by the transient fluctuation of mirror loss (total net threshold gain), and depends on the grating phases at the cleaved facets. Theoretical results predict that in the PC-LDs, mirror loss is insensitive to the grating facet phases due to a unique waveguide, which consists of a corrugated waveguide near the antireflection-coated front facet and an uncorrugated waveguide near the high- reflection-coated rear facet. Therefore the variation of phase conditions for oscillation caused by the external optical feedback gives rise to a relative low transient fluctuation of the mirror loss that suppresses the positive feedback effect of mirror loss, as well as the optical output fluctuations. Furthermore, optimum-grating length, i.e. 150 micrometers for 250 micrometers cavity length, was derived by the calculations. The relative intensity noise (RIN) caused by external optical feedback was measured for PC-LDs with different grating length over a wide feedback level range from -40 dB to -20 dB. Experimental results show that, for the cavity length of 250 micrometers , the PC-LDs with a grating length of 150 micrometers have the most excellent external optical feedback resistant characteristics. The increase of RIN was suppressed to as low as -126 dB/Hz with the external optical feedback of -20 dB. These results agreed well with the theoretical analysis.

Higher quality video formats beyond HDTV are being developed, but these formats require data comm... more Higher quality video formats beyond HDTV are being developed, but these formats require data communication rates greater than 10 Gbps, which are not easily adaptable to household applications. Moreover, household usage requires ease of handling, robustness against poor connectivity, and affordable cost. Conventional silica optical fibers are not suitable for applications that involve high-speed, short-range communication, because of their fragility, and difficulty in achieving precise connectivity with a low cost connecting method. We proposed a novel expanded-beam interconnect using a graded-index plastic optical fiber (GI POF) with a glass spherical collimator lens uniquely fabricated by low cost ballpoint-pen technologies at both ends. Our power budget evaluation verified its suitability for consumer applications. Successful validation was then conducted by transmitting 4K-3D uncompressed video content.

A 40-Gb/s receiver module with an InAlAs waveguide avalanche photodiode has developed for the fir... more A 40-Gb/s receiver module with an InAlAs waveguide avalanche photodiode has developed for the first time. We have achieved the minimum received power of -18 dBm, which is the highest sensitivity ever reported without fiber amplifiers

Optical Fiber Communication Conference, 1989

Journal of Lightwave Technology, 1990

ABSTRACT Twelve-channel 14-Mb/s/channel 1-km parallel optical-fiber transmission using a 1×12 low... more ABSTRACT Twelve-channel 14-Mb/s/channel 1-km parallel optical-fiber transmission using a 1×12 low-drive-current 1.3-μm light-emitting diode (LED) linear array and an InGaAs p-i-n photodiode linear array, with the LED drive current as low as 12 mAp-p/channel, is discussed. No receiver sensitivity degradation has been observed under simultaneous 12-channel operation. The skew was less than 6 ns after transmission through a 1-km-long 12-channel optical-fiber cable, which was sufficiently small for 14-Mb/s parallel transmission

Electronics Letters, 1988

ABSTRACT High-performance, long-wavelength OEICs on a GaAs-on-InP heterostructure were fabricated... more ABSTRACT High-performance, long-wavelength OEICs on a GaAs-on-InP heterostructure were fabricated. For the transmitter OEIC, high-speed operation up to 2.4 Gbit/s was achieved, and a receiver sensitivity as high as -26.0 dBm for a 1.2 Gbit/s NRZ signal was realised for the receiver OEIC. To confirm the usefulness of these OEICs for optical fibre networks, a 1.2 Gbit/s optical fibre transmission experiment was successfully carried out over a 52.5 km span

Optical Fiber Communication, 1986

InGaAs/lnP avalanche photodiodes (APDs) are the most promising detectors for long-wavelength opti... more InGaAs/lnP avalanche photodiodes (APDs) are the most promising detectors for long-wavelength optical fiber communication systems.1-3 Moreover, planar APDs with a successful guard ring (GR) are demanded for practical use. This paper reports a newly developed planar InGaAs APD with a preferential lateral extended guard ring (PLEG).