[Show abstract][Hide abstract] ABSTRACT: This letter presents a polymer thermo-optic totalinternal-reflection digital optical switch (TIR-DOS) with an index contrast of 1.5%- operating at low power consumption. The structure of our TIR-DOS was created by adding a reflection port to that of a conventional multimode filtering variable optical attenuator. To improve the total-internalr-eflection efficiency, a heater offset was applied to the crossing region of multimode waveguides of the TIR-DOS. The fabricated TIR-DOS shows a low electrical power consumption of 18 mW for an on-off ratio of 35 dB.
[Show abstract][Hide abstract] ABSTRACT: We have fabricated modules of 8-channel multi-wavelength lasers (MWLs) with a wavelength separation of 200 GHz for the wavelength division multiplexed-passive optical network (WDM-PON) optical line terminal sources. The variation in the output power is minimized by inserting silicone between the superluminescent diode (SLD) and the silica waveguide. The wavelength shift of each channel is less than 0.21 nm from the ITU grid and can be controlled in the range of 0.36 nm without any reductions of the output power by a tuning heater. MWLs operated successfully in the direct modulation for 1.25 Gbit/s transmissions over 20 km.
[Show abstract][Hide abstract] ABSTRACT: This letter presents a crosstalk-enhanced polymer thermo-optic digital optical switch operating at a low power consumption. Modified radiation-type attenuators are integrated in a series with a conventional 1×2 digital optical switch. A low optical crosstalk of less than -45 dB is attained at a low applied switching power of 60 mW, and an insertion loss of about 1.1 dB is exhibited.
[Show abstract][Hide abstract] ABSTRACT: We report the design and fabrication of a novel 1.55-m spot-size converter superluminescent diode (SLD) for optical access networks. The active section of SLD was fabricated by using a planar buried heterostructure to adopt the double-waveguide-core structure for low-threshold and high-output power operation at a low injection current. A ridge-based passive waveguide was employed for an efficient coupling to a planar lightwave circuit. The threshold current was as low as 14 mA, and the maximum output power was as high as 28 mW with ripple less than 3 dB at an injection current of 200 mA.
[Show abstract][Hide abstract] ABSTRACT: Transmit-receive devices (TRD) monolithically integrated with a butt-coupled semiconductor optical amplifier (SOA) have been designed and fabricated using a buried ridge/ridge waveguide structure with low-threshold-current and high-temperature operation characteristics. The maximum output power was 31 mW under CW operation at 25 °C. At 85 °C the output power was over 9 mW with a side mode suppression of over 45 dB. The responsivity of the detector photodiode was over 0.6 A/W in the temperature range between 25 and 65 °C and over 0.3 A/W at 85 °C. It was nearly constant in the input-power range between -30 to -10 dBm.
No preview · Article · May 2008 · Japanese Journal of Applied Physics
[Show abstract][Hide abstract] ABSTRACT: 10 Gbps data transmission was demonstrated with electroabsorption modulators integrated with a 4-channel wavelength division multiplexing transmitter composed of distributed Bragg reflector (DBR) lasers. A selective area growth technique was employed for the control of bandgap energy in the gain, modulator and passive sections. Then the laser and modulator stripes were fabricated by a buried heterostructure process. The DBR lasers showed uniform threshold currents between 5 and 10 mA, while the slope efficiency was around 0.11 W A−1. By controlling the DBR currents, a 4-channel transmitter was achieved for the channel spacing of 100 GHz (0.8 nm). The electroabsorption modulator showed clear eye openings under 10 Gbps non-return-to-zero modulation. It allowed 10 Gbps error-free operation over a 25 km long single-mode fiber.
No preview · Article · Apr 2008 · Semiconductor Science and Technology
[Show abstract][Hide abstract] ABSTRACT: We propose and demonstrate very compact multiwavelength lasers (MWLs) with a novel configuration designed to remove the mode hopping in the modulation region and separate the wavelength-tuning of each channel for cost-effective optical line termination sources in the wavelength-division-multiplexing passive optical network. The mode hopping of MWLs in the modulation region was eliminated by wavelength trimming using a tuning heater. The MWLs operated successfully in direct modulation for 1.25-Gb/s transmission over 20 km.
[Show abstract][Hide abstract] ABSTRACT: A 4-channel wavelength division multiplexing transmitter was fabricated with an array of distributed Bragg reflector (DFB) lasers monolithically integrated with 10-Gbps electroabsorption (EA) modulators. A selective area growth technique was employed for the control of bandgap energy in the gain and modulator sections. Then the laser and modulator stripes were fabricated by a buried heterostructure process. The DBR lasers showed uniform threshold currents between 5-10 mA , while the slope efficiency was around 0.11 W/A. By controlling the DBR currents, a 4-channel transmitter was achieved for the channel spacing of 100 GHz (0.8 nm). The 3-dB bandwidth of the EA modulator was measured to be over 10 GHz for all bias voltages. The EA modulator showed clear eye openings under 10-Gbps non-return-to-zero modulation. It allowed 10-Gbps error-free operation over a 25-km long single mode fiber.
[Show abstract][Hide abstract] ABSTRACT: We have demonstrated a very compact eight-channel 200-GHz-spacing multiwavelength laser (MWL) module for the optical line terminal source of wavelength-division-multiplexing passive optical network. The wavelength shift of MWLs and external cavity lasers from the ITU grid was within +0.14 nm for eight channels, which was well matched to the target wavelength shift of less than plusmn0.2 nm. The oscillation characteristics of our MWL module are better than those of conventional MWLs with hybrid integration.
No preview · Article · Nov 2007 · IEEE Photonics Technology Letters
[Show abstract][Hide abstract] ABSTRACT: We successfully fabricated a very compact 8-channel 200 GHz-spacing multi-wavelength laser (MWL) module for WDM-PON OLT source. The wavelength shift of MWL from ITU grid was within - 0.25nm for the 8- channels, which was well matched to target wavelength shift of less than 0.2nm. This module operates successfully with a total throughput of 1.25 Gbit/s over 20 Km transmission.
[Show abstract][Hide abstract] ABSTRACT: We report a high performance integrated transmit-receive-device (TRD) with a butt-coupled SOA by a well established procedure for the first time. The responsivity was same in input power range from -30 to -10dBm due to integrated SOA. The responsivity of more than 0.3 W/A was obtained until the 85degC temperature range.
[Show abstract][Hide abstract] ABSTRACT: The optimization of a waveguide photodiode (WGPD) having a thin absorption layer is discussed. Responsivity of 1.09 A/W was achieved. More than 100 A thick absorption layer is required for high responsivity and low polarization dependency. A formula for frequency response in a WGPD with a thin absorption layer is obtained.
[Show abstract][Hide abstract] ABSTRACT: This paper introduces optical devices for G-bit WDM- PON system. We have developed WDM-PON ONU employing the reflective semiconductor optical amplifier(R-SOA) and 16 ch WDM-PON OLT which is fabricated by the hybrid integration technology.
[Show abstract][Hide abstract] ABSTRACT: The optimization of a waveguide photodiode (WGPD) having a thin absorption layer is discussed. With an absorption layer thickness of less than 0.1 mum, responsivity of 1.09 A/W was achieved for lensed-fiber coupling. For flat-ended fiber coupling, responsivity of 0.93 A/W was achieved. An absorption layer thickness of more than 100 A˚ is required for high responsivity and low polarization dependency. A formula for frequency response in a WGPD with a thin absorption layer is also obtained. This formula gives the optimized WGPD structure for high speed operation with high responsivity.
No preview · Article · Feb 2007 · Applied Physics Letters
[Show abstract][Hide abstract] ABSTRACT: We investigate on the variation of loss and temperature dependence of a polymeric arrayed waveguide grating (AWG) depending on its substrate, by fabricating 16-channel polymeric AWGs with various substrate conditions. Insertion loss for a polymeric AWG on a silicon substrate is measured as low as 3.1 dB. The temperature-dependent wavelength shift for a polymeric AWG detached from the substrate is maintained within 0.1 nm from 20 to 80 °C. But we observe a degradation of insertion loss and a little instability in wavelength characteristics both for the detached polymeric AWG and for a polymeric AWG on a polymer substrate. We investigate on those optical properties of the polymeric AWGs based on measured thermal expansion properties of the polymers.
No preview · Article · Feb 2007 · Optics Communications
[Show abstract][Hide abstract] ABSTRACT: A PIN photodiode having a low dark current of 1.35 nA and a high external quantum efficiency of 95.3% fabricated for a passive optical network receiver. As the current was increased under a high voltage of 38 V and a temperature of , it was observed that there is a threshold current at 11 mA which induces a junction failure. Experimental data suggest that the junction failure occurs due to the crystal breaking at the end facet as a result of thermal heat or energetic carriers. This threshold behavior of junction failure is a valuable observation for the safe treatment of photodiodes. As long as the current is limited below the threshold currents, we have not observed failure events of our photodiodes.
[Show abstract][Hide abstract] ABSTRACT: A very compact 16-channel 200 GHz-spacing transmitter module was fabricated for wavelength division multiplexing-passive optical network (WDM-PON) optical line termination (OLT) source. The transmitters are composed of reflection gratings and hybrid integrated superluminescent laser diodes (SLD) to construct 16-channel external cavity lasers (ECLs) on the planar lightwave circuit (PLC) chip.
[Show abstract][Hide abstract] ABSTRACT: A distributed Bragg reflector (DBR) laser and a high speed electroabsorption modulator (EAM) are integrated on the basis of the selective area growth technique. The typical threshold current is 4 to 6 mA, and the side mode suppression ratio is over 40 dB with single mode operation at 1550 nm. The DBR laser exhibits 2.5 to 3.3 mW fiber output power at a laser gain current of 100 mA, and a modulator bias voltage of 0 V. The 3 dB bandwidth is 13 GHz. A 10 Gbps non-return to zero operation with 12 dB extinction ratio is obtained. A four-channel laser array with 100 GHz wavelength spacing was fabricated and its operation at the designed wavelength was confirmed.
[Show abstract][Hide abstract] ABSTRACT: We present a 16-channel polymeric AWG on silicon substrate with insertion loss as low as 3.1dB, and a free-standing polymeric AWG with the temperature-dependent wavelength deviation as low as 0.1nm from 20 to 80°C.
[Show abstract][Hide abstract] ABSTRACT: A method for polymer planar lightwave circuit (PLC) devices fabricated on a substrate with V-grooves is developed for passive alignment of an optical fiber to a polymer waveguide. In order to minimize thickness nonuniformity of polymer layers caused by the V-grooves, dry film resist (DFR) is used. The V-grooves are covered with the DFR before the polymer layers are spin-coated on the substrate. The DFR prevents the polymer from being filled in the V-grooves as well as from being spin-coated nonuniformly on the substrate. This process provides a simple and cost-effective fabrication method of polymer PLCs or platforms for passive alignment.
No preview · Article · Dec 2005 · Optics Communications