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Kazuya Nagashima - IEEE Xplore Author Profile

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We developed the world's first InP-based C+L-band coherent driver modulator (CDM) that has a 3-dB electro-optic (EO) bandwidth of over 90 GHz. The CDM consisted of an InP-based n-i-p-n heterostructure twin IQ modulator chip with a differential capacitively loaded traveling-wave electrode, a SiGe BiCMOS driver in an open-collector configuration, and an RF package with a flexible printed circuit as ...Show More
We propose an ultra-compact CPO transceiver based on 1060-nm coupled-cavity single-mode VCSEL array and single-mode MCF, with double-sided FC-bonding and direct MCF butt-coupling. The fabricated 25-Gb/s × 16-channel CPO is as small as < 1 cm3. We demonstrate 2-km optical transmission covering inside of data-centres.Show More
We report a design and optical link characteristics of an ultra-compact 106-Gb/s PAM4 × 8-channel linear-drive VCSEL-based transceiver for Co-Packaged Optics. This optical transceiver employs the record narrowest 0.3-mm-pitch LGA for the electrical interface. To expand the bandwidth, we use a core-less building-up multi-layer organic substrate to avoid impedance mismatch of the vias in the core la...Show More
We report a design and characteristics of an electrical pluggable interface and a testing station for a 50- Gbaud x 16-channel CPO transceiver using a 0.3-mm-pitch LGA interface. This testing station has a 3-dB bandwidth of 27.1 GHz at the longest differential transmission line, which is sufficient for 50-Gbaud signal transmission. We also build an optical link employing a 53-Gbaud x 8-channel opt...Show More
We build a thermal simulation model and a temperature distribution measurement system for a CPO daughter board which accommodates 32 ultra-compact optical transceivers. Our unique water-cooling system prevent providing the heat of switch ASIC to the optical transceivers. A targeted case temperature of $\leq \mathbf{40}{{}^{\circ}\mathbf{C}}$, in order to keep a VCSEL temperature of $\leq \mathbf{5...Show More
This paper describes the design and transmission characteristics of a bandwidth-expanded testing station using a 0.3-mm-pitch LGA-based electrical pluggable interface for a $\mathbf{25}- \mathbf{Gbaud} \times \mathbf{16}-\mathbf{channel}$ optical transceiver. This testing station employs a core-less building-up multi-layer organic substrate to avoid impedance mismatch at the vias in a core layer. ...Show More
We evaluate an optical link employing an ultra-compact 850-nm MM VCSEL-based 56-Gb/s $\mathbf{PAM}\mathbf{4} \times \mathbf{8}-\mathbf{channel}$ optical transceiver and three different kinds of MMFs (i.e., OM3, OM4, and OM5 fibers). We particularly analyze jitter margin characteristics for serial and 8-channel parallel signal transmissions. TDECQ values are also measured for optical eye diagrams t...Show More
We developed an InP-based coherent driver modulator (CDM) with a flexible printed circuit (FPC) RF interface. The CDM has a 3-dB electro-optic (EO) bandwidth of over 85 GHz, including the evaluation board loss, which is sufficient for 1-Tb/s/λ-class operation. Furthermore, we obtained good back-to-back bit-error-rate (BER) performance in modulations up to 144-Gbaud dual-polarization 16-QAM, and we...Show More
We report the designs and characteristics of electrical pluggable interface using a 0.3-mm-pitch LGA for a 25-Gbaud x 16-channel CPO transceiver and a testing station using the electrical pluggable interface. The testing station has a TEC-integrated temperature control unit attached to the bottom of test board. Differential transmission lines for the test board were designed with the aid of electr...Show More
We report the design and transmission characteristics of 56-Gb/s PAM4 × 8-channel VCSEL-based optical transceiver for Co-Packaged Optics and 400-Gb/s QSFP-DD AOCs. This optical transceiver employs the world smallest 0.3-mm pitch LGA for the electrical interface. When operating the module by a bit stream of 56-Gb/s PAM4 PRBS-13Q in a loopback link system, we observed that the BER is less than the K...Show More
We design a CPO daughter board on which 32 ultra-compact transceivers are mounted with an FPGA. The high-speed differential transmission lines are designed with the aid of electro-magnetic simulations. Eye diagrams are simulated by high-speed circuit simulations. Measured 25-Gbaud NRZ eye diagrams have a good agreement with the simulated results. Electrical crosstalk was suppressed to −30 dB and l...Show More
We developed flexible printed circuit RF interface InP-based coherent driver modulators with a 3-dB bandwidth of over 80 GHz for 128-Gbaud or higher operations. Low insertion loss (<8.5 dB per polarization), low polarization-dependent loss (<0.1 dB), and high extinction ratio (>30 dB) were achieved.Show More
We developed a flexible printed circuit (FPC) RF interface InP-based high-bandwidth coherent driver modulator (CDM) for 128-Gbaud class operations. To increase the bandwidth of the CDM, an FPC RF interface was introduced to the CDM package, which significantly improved the roll-off frequency by about 40 GHz compared with a conventional package with a surface-mount-type RF interface. The FPC packag...Show More
This paper gives a detailed description of a >1.3-Tb/s VCSEL-based on-board parallel-optical transceiver module for high-density optical interconnects. The optical module integrates a 28-Gb/s × 24-channel transmitter and receiver into one package with a 1-in2 footprint, thereby yielding a data rate density as high as 1.34 Tb/s/in2. A unique module design is developed to utilize the whole top surfa...Show More
We demonstrate a 28-Gb/s × 24-channel on-board optical transceiver operated under an air-cooling environment. The optical transceiver realizes a data rate density as high as 1.34 Tb/s/inch2 with a total power consumption of 9.1 W. A unique packaging structure of the transceiver enables using the whole top surface for thermal dissipation by the aid of air-cooling heatsink. The optical module realiz...Show More
We demonstrate >1.3-Tb/s VCSEL-based on-board optical module for high-density optical interconnects. The optical module integrates 28-Gb/s × 24-channel transmitter and receiver into one package of 1-inch2 footprint. Subsequently, the total data rate is as high as 1.34 Tb/s. As investigated the temperature distributions of an optical module in calculation and experiment, an operating case temperatu...Show More
We demonstrate a >1-Tb/s VCSEL-based on-board optical engine for high-density optical interconnects. The optical engine integrates 28-Gb/s × 24-channel transmitter and receiver into one package of 1-inch2 footprint. Hence, the total data rate is as high as 1.34 Tb/s. The thermal simulation is performed when operating all 24 channels with the total power of 9.1 W with CDR and 6.0 W without CDR, ass...Show More
We report the thermal design of 28-Gb/s × 24-channel CDR-integrated VCSEL-based transceiver optical module for high density optical interconnects. The transceiver module realizes a very high data rate density of 1346 Gb/s/inch2 at a total power consumption of 9.1 W. A unique design of this optical module realizes to use the whole top surface for thermal dissipation. We performed thermal simulation...Show More
A solderable 28-Gb/s × 4-channel VCSEL-based optical transceiver module was designed for QSFP28 MPO-type transceiver and AOC applications. The module exhibits 28.05-Gb/s × 4-channel simultaneous operation with a jitter margin of -0.4 U.I. at the case temperature of 70 °C. The 4-channel module can be simply mounted on a PCB in compliance with the standard of QSFP28 edge connector, together with oth...Show More
We demonstrate 4-channel miniature solderable VCSEL-based optical modules with an integrated clock-data-recovery (CDR) circuitry for 100-Gb/s applications. We also propose to use a 1060-nm VCSEL-based optical link using the module and a conventional OM2 fiber cable to reduce the total link cost. When operating the module by a bit stream of 28.05-Gb/s, 231-1 PRBS in the built link system, we observ...Show More
We demonstrate a very high density 28-Gb/s × 24-channel CDR-integrated VCSEL-based optical transceiver module. The optical module achieves a very high data rate density of 1344 Gb/s/inch2 (2.08 Gb/s/mm2). An optical link employing the optical module achieved a jitter margin of 0.48 U.I. at a BER of 10-12 at case temperatures ranging from 31 °C to 70 °C with a very low link power of 13.5 mW/channel...Show More
We report successful achievement of a record long distance error-free transmission of 1000-m 50- $\mu \text{m}$ -core multi-mode fiber (MMF) in a non-return-to-zero 25.78-Gb/s modulated vertical cavity surface emitting laser-based optical link using four-channel miniature parallel-optical modules. The optical power is centralized within the core of MMF by an active alignment assembly. The restrict...Show More
We report a solderable 4-channel VCSEL-based optical transceiver module perfect for high-volume production of QSFP AOCs. The 4-channel module can be simply mounted on a PCB together with other electronics components through a solder reflow process. We fabricated a PCBA in compliance with the standard of QSFP edge connector. The PCBA has an MCU written with a firmware included with a look-up table ...Show More