An integration of the access/backbone network is expected to become indispensable in the future. We analyze the current and future optical networks and we describe the promising technologies. GMPLS architecture in backbone networks and WDM PON architecture in access networks will play the most important roles. We overview recent studies on the access/backbone integrated network to achieve guaranteed QoS. We also describe the developed system architecture as a milestone toward the access/backbone integrated network.

This paper describes two different types of GaAs-HBT compatible, base-collector diode 0/20-dB step attenuators--diode-linearizer type and harmonics-trap type--for 3.5-GHz-band wireless applications. The two attenuators use an AC-coupled, stacked type diode switch topology featuring high power handling capability with low bias current operation. Compared to a conventional diode switch topology, this topology can improve the capability of more than 6 dB with the same bias current. In addition, successful incorporation of a shunt diode linearizer and second- and third-harmonic traps into the attenuators gives the IM3 distortion improvement of more than 7 dB in the high power ranging from 16 dBm to 18 dBm even in the 20-dB attenuation mode when IM3 distortion levels are basically easy to degrade. Measurement results show that both the attenuators are capable of delivering power handling capability (P0.2 dB) of more than 18 dBm with IM3 levels of less than -35 dBc at an 18-dBm input power while drawing low bias currents of 3.8 mA and 6.8 mA in the thru and attenuation modes from 0/5-V complementary supplies. Measured insertion losses of the linearizer-type and harmonics-trap type attenuators in the thru mode are as low as 1.4 dB and 2.5 dB, respectively.

A new method of cancellation of IM3 using current feedback has been proposed for a multi-stage RFIC amplifier. In order to cancel the IM3 present in an output signal of the amplifier, the IIP3 level and IM3 phase of the amplifier are adjusted by means of feedback circuit techniques, so that the target specification is satisfied. By estimating the IIP3 level and IM3 phase variations for two states in situations with and without feedback possessing linear factors, the parameters of a feedback circuit can be calculated. To confirm the validity of the method, we have investigated two approaches; one including an analytical approach to designing a two-stage feedback amplifier, achieving an IIP3 level improvement of 14.8 dB. The other method involves the fabrication of single-stage amplifiers with and without feedback, operating at 850 MHz, both of which were designed as an integrated circuit using a 0.18 µm SiGe BiCMOS process. The fabricated IC's were tested using a load-pull measurement system, and a good agreement between the estimated and measured IIP3 level and IM3 phase variations has been achieved. Further studies show that the error in these variations, as estimated by the method, has been found to be less than 1.5 dB and 15 degrees, respectively, when the load admittance at 1701 MHz was greater than 1/50 S.

We have numerically evaluated the filtering characteristics of two vertically coupled microring resonator filters. In this evaluation we used the finite-difference time-domain method as the numerical analysis method. The structure we designed allows only a specific wavelength to pass. The filtering characteristics of this structure can be altered by changing the layout of the microring resonator. By using this structure the interval between peak wavelengths at a specific wavelength in the output spectrum can be increased. Specifically, the interval between peak wavelengths can be increased from 20 nm to 40 nm at wavelengths near 1.46 µm.

An integrated multi-level simulation environment is developed for a highly collision-resistant RFID system. An analog/mixed-signal (AMS) simulator for a circuit-level description of analog front-end power/signal transmission through electro-magnetic coupling is concurrently connected to a tailored software simulator for system-level description of digital back-end processing of TH-CDMA based anti-collision communication. The feasibility of the RFID system in which more than 1,000 transponders can be identified by a single reader in 400 msec is successfuly explored, under a practical presence of field disturbances such as background noises in communication channels as well as variations of electro-magnetic coupling strengths for power transmission.

Power supply noise waveforms are acquired in a voltage domain by an on-chip monitor at resolutions of 0.3 ns/1.2 mV, in a digital test circuit consisting of 0.18-µm CMOS standard logic cells. Concurrently, magnetic field variation on a printed circuit board (PCB) due to power supply current of the test circuit is measured by an off-chip magnetic probing technique. An equivalent circuit model that unifies on- and off-chip impedance network of the entire test setup for EMI analysis is used for calculating the on-chip voltage-mode power supply noise from the off-chip magnetic field measurements. We have confirmed excellent consistency in frequency components of power supply noises up to 300 MHz among those derived by the on-chip direct sensing and the off-chip magnetic probing techniques. These results not only validate the state-of-the art EMI analysis methodology but also promise its connectivity with on-chip power supply integrity analysis at the integrated circuit level, for the first time in both technical fields.

The proton-exchanged waveguide formed on MgO-doped lithium niobate crystals is resistant to the optical damage or the photorefractive effect. Therefore, this waveguide is believed to be a promising device for optical information and processing. However, the optical damage can also be an important problem for this waveguide in the communication wavelength since the high-power optical source is used. In this report, a brief general review on the optical properties and its practical application of the lithium niobate crystal as the optical waveguide are given. Then the experimental research work aimed to clarify the properties and its mechanism of the electrooptic effect and the optical damage or photorefractivity of the lithium niobate optical waveguide is described. In this work, the optical damage in this proton-exchanged waveguide is measured quantitatively at various optical wavelengths including blue and red light by using the holographic grating method and the infrared communication wavelength (1550 nm) by using the prism coupler method. The optical damage is significant not only in blue wavelength but also in the red, and even at 1550 nm with high power (100 mW) laser diode for communication. So the optical damage cannot be negligible also in the communication wavelengths. The effect of annealing temperature is also discussed. At the relatively high temperatures, the optical damages are founde to be annealed out. The effect of the applied electric field to the optical damage is experimentally discussed and its enhancement is observed to the applied d.c. and a.c. fields. In conclusion, the optical properties as the electrooptic constant and the optical damage are experimentally measured and the many fundamental data are obtained to realize the useful and practical optical devices.

Autocloned photonic crystals have corrugated multilayer structure. By related process technology, we can easily fabricate an array of polarizers or waveplates. Patterned photonic crystals are versatile component of many optical systems. This paper focuses on their use in optical microscopy. The main topics are: 1. Use of polarization imaging in microscopy, 2. generation of radial/circular polarization by a polarizer having concentric corrugations, 3. a "longitudinal polarization slit" (a new component) and its function in confocal microscopy, and 4. a polarization converter for generating "z-polarized" light at the focal point. In every application above, autocloned photonic crystals play a central role.

An 8ch, 400 GHz monolithically integrated WDM channel selector featuring an array of quantum well semiconductor optical amplifiers (SOA) and arrayed waveguidegrating demultiplexer is presented. Reduction of fabrication complexity was achieved by using a single step selective area MOVPE to realize the different bandgap profiles for the SOA array and passive region. The selective growth mask dimensions were optimized by simulation. Dry-etching with short bending radii of 200 µm resulted in compact device size of 7 mm2.5 mm. Static channel selection with high ON-OFF ratio of >40 dB was achieved.

One approach to accommodating IP traffic on a wavelength division multiplexing (WDM) network is to construct a logical topology, establishing a set of lightpaths between nodes. The lightpaths carry IP traffic but do not require any electronic packet processing at intermediate nodes, thereby reducing the load on those nodes. When the IP and WDM networks have independent routing functions, however, the lightpaths in the WDM network may not be fully utilized by the IP router. It is therefore necessary to integrate the two routing mechanisms in order to utilize resources efficiently and adapt to changes in traffic. In this paper, we propose an integrated routing mechanism for IP over WDM networks. The key idea is to first prepare a set of virtual-links representing the lightpaths that can be established by the WDM network, then calculate the minimum cost route on an IP network including those links. Our simulation results show that when traffic patterns do not change, the throughput of our method is almost the same as that of a logical topology optimally designed for a given traffic demand. When traffic patterns change, the throughput of our method is about 50% higher than that of the logical topology.

This paper discusses issues in the design of analog-to-digital converters (ADCs) in nanoscale CMOS and introduces some experimental designs incorporating techniques to solve these issues. Technology scaling increases the maximum conversion rate, but it decreases the gain and the SNR. To maintain a high SNR level despite the low-voltage operation, the power consumption needs to be increased. Because of lowered supply voltages, the design of circuits based on operational amplifiers (OpAmps) has become more difficult. Designs without OpAmps have therefore received more attention. One way of realizing low-voltage pipeline ADCs is by using comparator-controlled current sources, instead of conventional OpAmps. Furthermore, successive approximation ADCs and sub-ranging ADCs do not require OpAmps and are therefore suitable for low-voltage operation. ADC designers are now searching for suitable architectures for future nanoscale CMOS processes.

Demands for the low power VLSI have been pushing the development of aggressive design methodologies to reduce the power consumption drastically. To meet the growing demand, we propose low power adders that adaptively select supply voltages based on the input vector patterns. First, we apply the proposed scheme to the Ripple Carry Adder (RCA). A prototype design by a 0.18 µm CMOS technology shows that the Adaptive VDD 32-bit RCA achieves 25% power improvement over the conventional RCA with similar speed. The proposed adder cancels out the delay penalty, utilizing two innovative techniques: carry-skip techniques on the checking operands, and the use of Complementary Pass Transistor Logic (CPL) with dual supply voltage for level conversion. As an expansion to faster adder architectures, we extend the proposal to the Carry-Select Adders (CSA) composed of the RCA sub-blocks. We achieved 24% power improvement on the 128-bit CSA prototype over a conventional design. The proposed scheme also achieves stand-by leakage power reduction--for 32-bit and 128-bit Adaptive RCA and CSA, respectively, 62% and 54% leakage reduction was possible.

We propose a simple technique to form miniature optical circuits using microfibers embedded into a low refractive index matrix. As an example we demonstrate a silica microfiber knot resonator embedded in a fluoroacrylate polymer. Fabrication issues and initial experimental results are reported. We also present simulations aimed at understanding the current limitations to the Q-factor and the role of the embedding polymer refractive index on the Q-factor of future resonators. It is anticipated that using commercially available polymers high Q-factor resonators with radii as small as 100 micrometers can be made by this technique.

We fabricated various microscopic optical devices with Si photonic wire waveguides and demonstrated their fundamental characteristics. The bending loss of the waveguide was practically negligible when the bending radius of the waveguide exceeded 5 µm. Therefore, we can fabricate very compact optical devices with the waveguide. We demonstrated an optical directional coupler with the waveguide. The coupling length of the directional coupler was extremely small, several micrometers, because of strong optical coupling between the waveguide cores. We also demonstrated ultrasmall optical add/drop multiplexers (OADMs) with Bragg grating reflectors constructed from the waveguides. The dropping wavelength bandwidth of the OADM device was less than 2 nm and the dropping center wavelength could be tuned using thermooptic control with a microheater formed on the Bragg reflector. Using the Si photonic wire waveguide, we also demonstrated thermooptic switches by forming a microheater on a branch of a Mach-Zehnder interferometer made up of the waveguides. In this switching operation, we observed an extinction ratio exceeding 30 dB, a switching power less than 90 mW, and a switching response speed less than 100 µs using a 12 optical switch with an 8530 µm2 footprint.

A novel structure of bandpass filter using NRD guide E-plane resonators is proposed. The NRD guide E-plane resonator is constructed by inserting metal foils in the E-plane of NRD guide. Simulation, fabrication and handling of the filter are very easy because each resonator is separated by simple metal foils. Chebyshev response bandpass filters are designed based on the theory of direct-coupled resonator filters and fabricated at 60 GHz. Simulated and measured filter performances agreed well with the design specifications. Insertion losses of the fabricated filters were found to be around 0.3 dB for 3-pole filter and 0.5 dB for 5-pole bandpass filter, respectively.

A linear CMOS transconductor is presented. PMOS transistors are employed in the resistor-replacement and voltage-level shifting to avoid the body effect. To annihilate the non-linear voltage terms, the substrate-bias effect of MOS transistors is treated more accurately in our design. Consequently, the non-linearity of the large-signal transconductance is reduced. The fabricated circuit occupies an area of 245 µm176 µm ( ≈approx 0.043 mm2) and dissipates 0.87 mW from a 3.3 V supply. For an input of 1 Vp-p, the measured output total harmonic distortion is less than 1.2%. The transconductance varies by less than 0.5% in the input range.

We achieved first dynamic all-optical signal processing with a bandgap-engineered MZI SOA all-optical switch. The wide-gap Selective Area Growth (SAG) technique was used to provide multi-bandgap materials with a single step epitaxy. The maximum photoluminescence (PL) peak shift obtained between the active region and the passive region was 192 nm. The static current switching with the fabricated switch indicated a large carrier induced refractive index change; up to 14 π phase shift was obtained with 60 mA injection in the SOA. The carrier recovery time of the SOA for obtaining a phase shift of π was estimated to be 250-300 ps. A clear eye pattern was obtained in 2.5 Gbps all-optical wavelength conversion. This is the first all-optical wavelength conversion demonstration with a bandgap-engineered PIC with either selective area growth or quantum-well intermixing techniques.

In this paper, we report a manufacturable InP DHBT technology, suitable for medium scale mixed-signal and monolithic microwave integrated circuits. The InGaAs/InP DHBTs were grown by MBE and fabricated using conventional process techniques. Devices with an emitter junction area of 4.8 µm2 exhibited peak cutoff frequency (fT) and maximum oscillation frequency (fMAX) values of 265 and 305 GHz, respectively, and a breakdown voltage (BVCEo) of over 5 V. Using this technology, a set of mixed-signal IC building blocks for ≥ 80 Gbit/s fibre optical links, including distributed amplifiers (DA), voltage controlled oscillators (VCO), and multiplexers (MUX), have been successfully fabricated and operated at 80 Gbit/s and beyond.

A new method to reduce power consumption of a linear transconductor is proposed in this paper. The minimum tail current for the operation of the transconductor is supplied by a new current source circuit. The proposed circuit is based on a dynamic biasing current technique. Results of SPICE simulation show that the proposed technique is very effective to reduce power consumption of the transconductor.

The analog IC technology, might sound old-fashioned, is still important for the future wireless systems such as 4G cellular phone systems, broadband wireless networkings, and wireless sensor networkings. The analog features and issues of the scaled CMOS transistor, the basic issue and the technology trend for the ADC as an important building block of wires systems, and the feature of the digital RF architecture proposed recently are reviewed and discussed. Higher speed and lower power consumption are expected for low SNR systems along with the further technology scaling. However, the high SNR system is not realized easily due to a decrease of signal voltage. One of the important technology trends is the digitalization of RF signal to realize the system flexibility, robustness, area shrinking, and TAT shortening.