Takaharu Ohyama

Design of a 10-Gb/s burst-mode optical packet receiver module and its demonstration in a WDM optical switching network

A 10-Gb/s burst-mode optical packet receiver module was fabricated. Its sensitivity was -24.8 dBm. Its sensitivity penalty due to packet-arrival timing jitter was less than 1.5 dB in arbitrary relative phase, and its total sensitivity penalty due to power fluctuation and packet-arrival timing jitter was less than 2.9 dB when the magnitude of packet-by-packet power fluctuation was 9 dB. We experimentally confirmed that our burst-mode optical packet receiver did not cause a penalty for wavelength division multiplexed (WDM) optical switching using the wavelength channel selector module.

Large-Capacity Compact Optical Buffer Based on InP Integrated Phased-Array Switch and Coiled Fiber Delay Lines

Optical buffering has been one of the major technical challenges in realizing optical packet switching (OPS) routers. While fiber-delay-line-based (FDL) buffers are the most practical and realistic solution to offer useful amount of capacity, the bulkiness of long FDLs and optical switches has been the main obstacle to practical implementation. This paper demonstrates a compact optical buffer with up to 750-ns capacity and 50-ns temporal resolution by using an InP integrated 1×16 optical phased-array switch and compact FDL module based on thin-cladding highly nonlinear fiber (HNLF). Owing to the high mode confinement inside HNLF, 15 fibers with the total length of 1.2 km are coiled onto a single bobbin with a coin-sized footprint without increasing the propagation loss. At the interface between the InP switch and FDLs, a pitch-converting silica planar-lightwave circuit chip is employed to achieve 16-port simultaneous uniform interconnection. Using the developed module, variable optical buffering experiment is demonstrated, where the packet intervals are expanded from 20 to 70 ns successfully.

High frequency electrical circuits on a planar lightwave circuit platform

We investigated the propagation losses and the characteristic impedances Z/sub L/ of coplanar waveguides (CPWs) and microstrip lines (MSLs) on a planar lightwave circuit (PLC)-platform formed on a silica/silicon substrate. The loss of the CPWs was 2.7 dB/cm at 10 GHz on the PLC-platform with 30 /spl mu/m thick silica layer. Thus, a cm-order circuit of this CPW is difficult to fabricate in the 10 Gb/s module. This is because the silicon substrate has a large loss tangent (tan /spl delta/). On the other hand, the loss of the MSLs, where a ground plane shielded the high loss silicon substrate, could be improved to 0.9 dB/cm at 10 GHz with 30 /spl mu/m thick polyimide. These lower loss MSLs on a PLC-platform can be applied to module operation at 10 Gb/s. Furthermore they have the advantage that they are suitable for application to array device circuits or circuits in a module where several devices are integrated because unlike CPWs the ground planes are not divided by signal lines or DC bias lines. The structure of CPWs and MSLs on a PLC-platform with a Z/sub L/ of 50 /spl Omega/ was also studied in detail.

A 10 Gb/s hybrid-integrated receiver array module using a planar lightwave circuit (PLC) platform including a novel assembly region structure

A planar lightwave circuit (PLC) platform for optoelectronic hybrid integration shows potential for achieving 10 Gb/s operation. It uses AuSn bump-type bonding pads on a silica layer to decrease parasitic capacitance, which limited the CR time constant in the optical chip assembly region, and two-layer electrical wiring to reduce parasitic inductance, which caused resonance in the electrical circuit region. An arrayed receiver module fabricated by integrating a two-channel monolithic opto-electronic integrated circuit (OEIC) chip on the PLC platform demonstrated a 3 dB-bandwidth of 8 GHz in both channels, which is equal to the bandwidth of the OEIC chip. This shows the feasibility of using this PLC platform for multichannel 10 Gb/s operation. Furthermore, this PLC platform can combine the versatile optical circuit functions of a PLC, such as an arrayed-waveguide grating wavelength multiplexer, with the high-speed signal processing function of mature electronic IC circuits. Consequently, this platform is a key device that will lead to high-capacity optical signal processing systems using optical wavelength/frequency routing.

All-in-One 112-Gb/s DP-QPSK Optical Receiver Front-End Module Using Hybrid Integration of Silica-Based Planar Lightwave Circuit and Photodiode Arrays

We propose a new hybrid integrated optical front-end module for a 100-Gb/s-class coherent receiver using silica-based planar lightwave circuit (PLC) technology. We have developed an integrated structure composed of multichannel microcollimator optics between PLC waveguides and photodiodes (PDs), and compact hermetically sealed optical-to-electrical converters with a PD array and a transimpedance amplifier array to maintain reliability. We used the technology to fabricate an all-in-one optical front-end module for a dual polarization quadrature phase-shift-keying (DP-QPSK) coherent receiver, and confirmed that the module operated successfully for 112-Gb/s DP-QPSK signal detection.

Hybrid integrated differential photoreceiver module for photonic packet switching systems using a planar lightwave circuit platform

A high-speed differential photoreceiver module for the photonic asynchronous transfer mode (ATM) packet switching system has been developed. This module employs a hybrid integration of a planar lightwave circuit (PLC) platform and a waveguide dual p-i-n photodiode. The PLC platform offered the optical signal processing functions of a tunable coupler and a half-bit delay line to handle Manchester-encoded optical signals. The flip-chip bonding of a dual p-i-n photodiode using AuSn solder bumps and a low-loss microstrip line enabled a very wide bandwidth larger than 20 GHz. This module successfully received 12-Gb/s Manchester-encoded optical signals. The module can be used in the broadcast-and-select photonic ATM switching nodes.

Assembly and wiring technologies on PLC platforms for low-cost and high-speed applications

The hybrid integration of silica-based planar lightwave circuit (PLC) platforms and semiconductor opto-electronic devices is a technology that shows promise for the development of highly functional opto-electronic modules. These modules are expected to offer both optical signal and electrical signal processing functions. The silica PLC has already realized various optical signal processing functions such as those in the couplers, the switches and the arrayed waveguide grating (AWG) wavelength multiplexers. Therefore, the technologies to improve the performance of electrical circuits on PLC platforms are significant to realize high-functional opto-electronic modules. We introduced a PLC platform with a silica-on-terraced silicon (STS) structure. Using the PLC platform, we can easily align optoelectronic devices to the silica waveguide. However, the silicon substrate caused parasitic capacitance and propagation loss in the electrical circuits on the platform.

Transmitter Optical Subassembly Using a Polarization Beam Combiner for 100 Gbit/s Ethernet over 40-km Transmission

A transmitter optical subassembly (TOSA) has been developed for a 100-Gbit/s Ethernet system for a long optical transmission distance over a 40-km single-mode fiber (SMF). To obtain a high optical output power and a high dynamic extinction ratio, the TOSA consists of two two-channel distributed feedback laser diode array chips integrated with electro-absorption modulators (EADFB laser array chips) with a 2 × 1 multimode interference (MMI) optical coupler and a polarization beam combiner for wavelength multiplexing. The TOSA is 8.7 mm × 28.7 mm × 6.5 mm including an LC-type receptacle. The TOSA has a twin collimator path for two EADFB laser array chips. The wavelength multiplexer consists of a mirror, a half-wavelength plate, and a polarization beam combiner. The TOSA could improve the optical output power by around 2 dB compared with a TOSA with a four-channel EADFB laser array chip and a 4 × 1 MMI optical coupler. An optical modulation amplitude of over 0.5 dBm and a mask margin exceeding 21% were obtained for each lane when all lanes were operated simultaneously with an EA modulator driving voltage of 1.5 V at a bit rate of 25.78125 Gbit/s, which fully satisfies the 100GBASE-ER4 specifications. We demonstrated error-free operation for an SMF transmission of over 40 km. Moreover, we confirmed that the TOSA was capable of error-free SMF transmission over 60 km with a power penalty of less than 1.4 dB.

WDM interconnection using PLC hybrid technology for 5 Tbit/s electrical switching system

We have developed a 500 GHz channel spacing 8-wavelength 2.5 Gbit/s optical interconnection system for a 5 Tbit/s electrical switching system. We fabricated compact WDM transmitter and receiver modules using PLC (planar lightwave circuit) hybrid technologies. An optical interconnection employing the optical modules together with a cyclic-frequency AWG (arrayed waveguide grating) router operated successfully.

High-speed optoelectronic hybrid-integrated transmitter module using a planar lightwave circuit (PLC) platform

High-speed optoelectronic hybrid-integrated transmitter module has been developed using a silica-based planar lightwave circuit (PLC) platform on which a laser diode (LD) array and a two-channel LD driver IC were integrated. Heat absorption through a highly thermal conductive silicon terrace kept the average output power constant to within 5% during IC operation. Bit-error-rate (BER) measurement showed that this module operated successfully with a 9-Gb/s nonreturn-to-zero (NRZ) signal. This indicates that the PLC platform does not have any adverse effect on the frequency bandwidth of the integrated chips. This approach, using the PLC platform for integrating optoelectronic devices and electronic ICs, will lead to the development of a high-speed optical multichip module for optical signal processing.