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Minoru Okamoto - IEEE Xplore Author Profile

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This paper reports 160-Gb/s optical time-division-multiplexed (OTDM) technologies including an all-optical integrated multiplexer (MUX) providing all-channel independent modulation, an all-optical integrated demultiplexer (DEMUX) that offers all-channel simultaneous demultiplexing, and a drift-free phase-locked-loop (PLL)-type clock recovery circuit for ultrahigh-speed OTDM signals. We present the...Show More
We achieved successful low-input-power (-10 dBm) wavelength conversion at 10 Gb/s by using a hybrid integrated cross-phase modulation wavelength converter (XPM-WC). The input CW power was also -10 dBm and the total current was only 215 mA, and no signal preamplifiers were used. From the relationship between the eye-opening ratio and the injection current to the SOA, we clarified the optimal curren...Show More
This letter provides the first report of 160-Gb/s optical time-division-multiplexed transmission with all-channel independent modulation and all-channel simultaneous demultiplexing. By using a multiplexer and a demultiplexer based on periodically poled lithium niobate and semiconductor optical amplifier hybrid integrated planar lightwave circuits, 160-km transmission is successfully demonstrated.Show More
We demonstrate 160 Gbit/s full time-division demultiplexing using a semiconductor optical amplifier (SOA) hybrid integrated demultiplexer in a planar lightwave circuit. Error-free demultiplexing from a 160 Gbit/s signal to 8 channel, 20Gbit/s signals is successfully demonstrated.Show More
We successfully achieved -10 dBm signal power and -10 dBm CW power operation using a hybrid integrated wavelength converter at 10 Gb/s without an optical preamplifier. Clear eye opening and a low power penalty less than 1 dB were achieved for all 8 slots.Show More
A laser with a reverse-V-shape layer exhibits a circular beam spot and low threshold current. The beam aspect ratio of the reverse-V-shape laser is clarified to be insensitive to reverse-V-shape width. The reverse-V-shape layer consists of a strained active layer and a passive guide layer, which leads to a low threshold current. The reverse-V-shape laser is attractive as an optical source for opti...Show More
We have demonstrated an optical transceiver diode integrated with a spot-size converter. We clarify that the design of a detection layer is essential for the temperature- and polarization-insensitive characteristics of the responsivity. Because the detection layer was introduced, 0.65 dB of responsivity deviation was obtained in the wide temperature range of -10/spl deg/C-85/spl deg/C with a high ...Show More
A double-heterostructure (DH) laser with TM mode lasing has been achieved with a narrow active-layer width, and a laser-diode optical switch (LDSW) module with less than a 0.35-dB gain difference between the TE and TM modes over a wide wavelength range has been constructed by introducing a square bulk active layer formed by dry etching and regrowth. The polarization-insensitive width of a 0.3-/spl...Show More
A spot-size converter integrated MQW laser with a tilted butt joint was fabricated to reduce reflection from the joint. It produced no degradation in bit error rate performance and repeatedly provided low threshold current and low coupling loss to the cleaved fiber in 2 inch wafer process.Show More
Structures of spot size converters that allow low loss and easy coupling between an optical semiconductor device and a fiber are proposed and designed theoretically. These spot-size converters have a tapered small core for expanding the mode field. They also have a double cladding region which consists of an n/sup +/-doped InP substrate as the outer cladding and a p-doped or nondoped InP layer as ...Show More
Summary form only given. A laser diode with a spot-size converter provides highly efficient coupling to the optical fiber without using lenses and provides a wide alignment tolerance in an optical module assembly. In this paper, the active region is optimized using a strained multiple quantum well (MQW) that has been buried with pn-heterostructure (pn-BH) to improve the maximum output power and la...
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A spot-size converted laser diode (SSC-LD) is an attractive device for low cost optical modules because it provides low-loss coupling to a single-mode fiber and to a Planar Lightwave Circuit (PLC) without using lenses as well as large alignment tolerance. Many intensive studies have been done in this field. We have recently developed 1.3 /spl mu/m-LDs with butt-jointed selectively grown spot-size ...Show More
Photoluminescence experiments on strained InAs/sub 0.48/P/sub 0.52/InP quantum wires show that the wire-width-dependent blue shift of the transition energy is much larger than the blue shift in lattice matched quantum wires. With magneto-luminescence measurements we are able to prove that lateral confinement effects only partly explain the observed blue shift. The other contribution comes from the...Show More
A 100-GHz optical pulse train is generated using an InP-based optical multiplexer. This device is based on a waveguide array with five paths of different lengths separated by a 10-ps propagation time. We used a multimode interference (MMI) splitter at the input and a taper-type combiner at the output. This device is well-suited for optical time-division multiplexing (OTDM) applications.<>Show More
A new approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of a tensile-strained-barrier MQW structure that enhances TM mode gain. Polarization sensitivity below 0.5 dB is realized at a wavelength of 1.56 /spl mu/m. A signal gain of 27.5 dB is obtained along with a saturation output power of 14 dBm. Deriving the refractive indices...Show More
A high-speed InGaAs/InAlAs multiple-quantum-well (MQW) intensity modulator and an InGaAsP/InGaAs MQW distributed feedback laser were monolithically integrated by using a hybrid growth technique combining molecular beam epitaxy and metalorganic vapor phase epitaxy. An operating drive voltage of only 2.0 V, a 20-dB on/off ratio, and a 3-dB bandwidth greater than 15 GHz were obtained. This device ope...Show More
Monolithic integration of an InGaAsP/InGaAs multiple quantum well (MQW) distributed-feedback (DFB) laser with a high-speed InGaAs/InAlAs MQW intensity modulator is demonstrated. A 3-dB bandwidth. in excess of 16 GHz and low-drive-voltage operation (4.0 V) for a 20-dB on-off ratio are obtained. Good coupling efficiency between an MQW DFB laser and an MQW modulator is accomplished using hybrid cryst...Show More
A novel tensile strained barrier (TSB) structure is proposed as the active layer to enhance the transverse-magnetic (TM) mode gain in long wavelength laser diodes. The band diagram of the TSB structure is described theoretically and experimentally. The gain difference between transverse-electric (TE) and TM modes is discussed for layers with various strain values and well layer thicknesses. The ch...
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A polarization-insensitive semiconductor optical amplifier was realized at a wavelength of 1.55 mu m. The active layer consisted of a tensile-strained-barrier multiple quantum well (MQW) structure. At a driving current of 150 mA, no dependence of the saturation characteristics on modes was obtained. The saturation output power at which the gain decreases 3 dB is 13.3 dBm. A slightly higher saturat...
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We present TM-mode gain enhancement of strained-layer superlattice (SLS) lasers and its application for a polarization-insensitive laser amplifier.
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Signal gain agreement between TE and TM modes is realized under a specific operation condition in a traveling wave type amplifier using a strained multiple quantum well structure for the first time. The signal gain of the TM mode completely agrees with that of the TE mode at an amplifier driving current of 70 mA. The identical signal gain is 7.5 dB at present. However, the signal gain could be eas...Show More