This paper proposes a universal structure for STM-N(N=1, 2, 3, ) multiplex line terminals that only utilizes N chips CMOS LSIs for Section OverHead (SOH) processing. The uniquely configured LSIs are applicable to any STM-N line terminal equipment. Reasonable frame alignment performance attributes, such as the maximum average reframe time, false in-frame time, out-of-frame detection time, and misframe time, are calculated for the configuration. A prototype SOH processing LSI built on 0.8m BiCMOS technology successfully realizes the functions needed for multiplex section termination. The STM-64 frame is also demonstrated using the proposed circuit configuration and prototype LSIs.

An ultra-compact InGaAs photodetector (PD) is demonstrated based on a photonic crystal (PhC) waveguide to meet the demand for a photoreceiver for future dense photonic integration. Although the PhC-PD has a length of only 1.7µm and a capacitance of less than 1fF, a high responsivity of 1A/W was observed both theoretically and experimentally. This low capacitance PD allows us to expect a resistor-loaded receiver to be realized that requires no electrical amplifiers. We fabricated a resistor-loaded PhC-PD for light-to-voltage conversion, and demonstrated a kV/W efficiency with a GHz bandwidth without using amplifiers. This will lead to a photoreceiver with an ultralow energy consumption of less than 1fJ/bit, which is a step along the road to achieving a dense photonic network and processor on a chip.

This paper proposed a fault localization and supervisory (SV) channel implementation for linear-repeaters (L-Reps) employing optical line amplifiers. In order to successfully introduce L-Reps into a Synchronous Digital Hierarchy (SDH)/Synchronous Optical Network (SONET)-based networks in a smooth, orderly fashion, layering of repeater section and supervisory system design must be taken into consideration. There supervisory techniques, such as linking analog-based and digital-based information, a precedence of digital-based information and an upstream precedence, for locating faulty L-Rep sections are proposed taking into consideration the difference in monitoring capabilities between L-Reps and regenerating-type repeaters (R-Reps). Furthermore, a linear repeater supervisory (LSV) channel configuration for L-Reps is also proposed. Finally, an SV system established in a prototype SDH-based 10-Gbit/s optical transmission system is briefly described.

Optical fiber transmission systems have advanced rapidly with the advent of highly advanced electronic and optical devices. This paper introduces several IC technologies required for ultra-high-speed optical transmission and overviews current IC technologies used for the existing and developing optical fiber trunk transmission systems. Future trends in device technologies are also discussed.

We demonstrate heteroepitaxial growth of GaAs/Ge buffer layers for fabricating 1.3-µm range metamorphic InGaAs-based multiple quantum well (MQW) lasers in which the Ge buffer layer is grown using a metal-organic Ge precursor, iso-butyl germane, in a conventional metal-organic vapor phase epitaxy reactor. This enables us to grow Ge and GaAs buffer layers in the same reactor seamlessly. Transmission electron microscopy and X-ray diffraction analyses indicate that dislocations are well confined at the Ge/Si interface. Furthermore, thermal-cycle annealing significantly improves crystalline quality at the GaAs/Ge interface, resulting in higher photoluminescence intensity from the MQWs on the buffer layers.

We present an 88 wavelength-routing switch (WRS) that monolithically integrates tunable wavelength converters (TWCs) and an 88 arrayed-waveguide grating. The TWC consists of a double-ring-resonator tunable laser (DRR TL) allowing rapid and stable switching and a semiconductor-optical-amplifier-based optical gate. Two different types of dry-etched mirrors form the laser cavity of the DRR TL, which enable integration of the optical components of the WRS on a single chip. The monolithic WRS performed 18 high-speed wavelength routing of a non-return-to-zero signal at 10 Gbit/s. The switching operation was demonstrated by simultaneously using two adjacent TWCs.

We propose and demonstrate a novel ladder interferometric filter that exhibits flat-topped spectral response for use in wavelength-division-multiplexing (WDM) based photonic networks. We numerically analyze the flattened spectral response in a ladder-type filter by modifying the transfer matrix of ladder interferometer. Conventional parabolic-shaped and flat-topped-designed ladder interferometric filters are fabricated, and characterized. We demonstrate a flat-topped filter response in the fabricated device. The shape factor, which is defined by the ratio of -1 dB bandwidth to -10 dB bandwidth, is improved from 0.32 to 0.54. The tunability and the increase in filter extinction ratio of the proposed device are also discussed.

This paper provides an architectural study of optical multiple-ring trunk-transmission networks using high-speed Time Division Multiplexing (TDM), and proposes two algorithms for distributed control environments. We propose a path-setup algorithm that uses Token protocol over Section Overhead (SOH) bytes, by which network-nodes communicate with each other to reserve bandwidth. A classified path restoration algorithm is also proposed that offers 3 path classes in terms of restoration performance. Class A paths, the most reliable, never lose any bit even against unpredictable disasters. They are realized by path-duplication at the source node, route diversity,and hitless switching at the destination node. Class B paths are restored by re-routing, where the original path-setup algorithm is reused. Class C paths are the most economical because a failed path is restored by maintenance action.

To meet the demand for light sources for on-chip optical interconnections, we demonstrate the continuous-wave (CW) operation of photonic-crystal (PhC) nanocavity lasers at up to 89.8 by using InP buried heterostructures (BH). The wavelength of a PhC laser can be precisely designed over a wide range exceeding 100 nm by controlling the lattice constant of the PhC. The dynamic responses of the PhC laser are also demonstrated with a 3-dB bandwidth of over 7.0 GHz at 66.2. These results reveal the laser's availability for application to wavelength division multiplexed (WDM) optical interconnection on CMOS chips. We discuss the total bandwidths of future on-chip optical interconnections, and report the capabilities of PhC lasers.

We have developed membrane distributed Bragg reflector (DBR) lasers on thermally oxidized Si substrate (SiO2/Si substrate) to evaluate the parameters of the on-Si lasers we have been developing. The lasers have InGaAsP-based multi-quantum wells (MQWs) grown on InP substrate. We used direct bonding to transfer this active epitaxial layer to SiO2/Si substrate, followed by epitaxial growth of InP to fabricate a buried-heterostructure (BH) on Si. The lateral p-i-n structure was formed by thermal diffusion of Zn and ion implantation of Si. For the purpose of evaluating laser parameters such as internal quantum efficiency and internal loss, we fabricated long-cavity lasers that have 200- to 600-µm-long active regions. The fabricated DBR lasers exhibit threshold currents of 1.7, 2.1, 2.8, and 3.7mA for active-region lengths of 200, 300, 400, and 600µm, respectively. The differential quantum efficiency also depends on active-region length. In addition, the laser characteristics depend on the distance between active region and p-doped region. We evaluated the internal loss to be 10.2cm-1 and internal quantum efficiency to be 32.4% with appropriate doping profile.

This paper proposes a parallel word alignment procedure for m Binary with 1 Complement Insertion (mBlC) or Differential m Binary with l Mark Insertion (DmBlM) line code. In the proposed procedure for mBlC line code, the word alignment circuit searches (m+1) bit pairs in parallel for complementary relationships. A Signal Flow Graph Model for the parallel word alignment procedure is also proposed, and its performance attributes are numerically analyzed. The attributes are compared with those of the conventional bit-by-bit procedure, and it is shown that the proposed procedure displays superior performance in terms of False-Alignment Probability and Maximum Average Aligning Time. The proposed procedure is suitable for high speed optical data links, because it can be easily implemented using a parallel signal processor operating at a clock rate equal to 1/(m+1) times the mBlC line rate.

We present a novel high-speed transmitter consisting of a frequency modulated DBR laser and optical filters. The refractive index modulation in the phase control region of the DBR laser allows high-speed frequency modulation. The generated frequency modulated signal is converted to an intensity modulated signal using the edge of the optical filter pass band. We present theoretical simulations of high-speed modulation characteristics and extension of transmission reach. With the proposed transmitter, we review the experimental demonstration of 180-km transmission of a 10-Gb/s signal with a tuning range of 27 nm and 60-km transmission of a 20-Gb/s signal.

Apodised chirped gratings based on InGaAsP/InP deep-ridge waveguides with vertical-groove surface gratings were fabricated. Reflectivity ripple and group delay ripple were reduced from around 4 dB to 1 dB and from around 5 ps to 2 ps, respectively, by apodisation over a wavelength range of around 20 nm.

Large-capacity photonic packet switch using the wavelength division multiplexing (WDM) technology is proposed. In this switch, the optical buffers, consisting of the fiber delay lines, are shared in many input ports by using the WDM. Furthermore, to reduce the number of optical buffers, the speed-up effect in the optical switch part is investigated. A high-speed tunable optical filter incorporating a semiconductor ring resonator is a key device in the proposed packet switch because many optical filters are used. Optical ring resonators should be possible to fabricate them at a low cost because of their simple structure. To achieve a wide tuning range we designed a double-ring structure, in which two ring resonators are connected in series, and fabricated it using the InGaAsP-InP material system. This device exhibits a total free spectral range (FSR) of 1.7 THz and contrast ratio of 9.5 dB. The ring radii are 25.2 and 17.8 µm, which correspond to FSRs of 340 and 425 GHz, respectively. The switching time of the device is 2.5 ns.