Yuta Ueda

Low-Loss Cascaded Mach–Zehnder Multiplexer Integrated

A 4 × 25-Gb/s electroabsorption modulator integrated with a distributed feedback (DFB) laser (EADFB laser) array monolithically integrated with a low-loss optical multiplexer (MUX) is developed for 100 GbE transmitters for the first time. A cascaded Mach-Zehnder (MZ) filter, which has no intrinsic loss, is used as the MUX. The design and fabrication of the MZ-MUX for 100 GbE are thoroughly described. The measured loss of fabricated MZ-MUX is 2-3 dB, which is improved by 4 dB compared with that of the conventional 1 × 4 multimode interference MUX. The MZ-MUX is monolithically integrated with a four-EADFB-laser array and the output power of the chip is increased by 3 dB compared with that of a conventional 4 × 25-Gb/s monolithically integrated chip. With the folded layout, the size of the chip is similar to that of the conventional chip. The fabricated chip is packaged into a very compact transmitter optical subassembly (TOSA). The system requirements are satisfied with semi-cooled operation, and very clear eye openings are obtained after 10-km single-mode-fiber transmission. The adjustment of filter spectra by current injection is also shown, and fine tuning is possible with very low injection current.

25\hbox{-}{\rm Gbit}/{\rm s}\times 4\hbox{-}{\rm Lane}

The first ultracompact transmitter optical subassembly for long-distance, beyond-100-Gbit/s data communication systems based on a monolithically integrated light source is developed, and 40-Gbit/s× 4 operation with the clear eye openings up to 10-km single mode fibre transmission is demonstrated.

EADFB Laser Array for Future CFP4 100 GbE Transmitter

We propose a novel approach for simultaneously controlling the chirp and increasing the output power of an EADFB laser by monolithically integrating a short-cavity SOA. We achieved a 40-Gbit/s 5-km SMF transmission at a wavelength of 1.55 μm by using an EADFB SOA with a lower power consumption than a stand-alone EADFB laser.

Ultracompact, 160-Gbit/s transmitter optical subassembly based on 40-Gbit/s × 4 monolithically integrated light source.

We fabricated a 400-G flip-chip interconnection eight-channel EADFB laser array module. The flip-chip interconnection technique provides a higher modulation bandwidth and lower electrical crosstalk than the wire interconnection technique. The 3-dB bandwidth of the flip-chip interconnection subassembly was about 50 GHz. And the electrical crosstalk of the flip-chip interconnection module was suppressed to less than -20 dB below 35 GHz. We obtained clear eye openings for all eight lanes under eight-channel 50-Gb/s simultaneous operation after a 10-km SMF transmission.

Novel approach for chirp and output power compensation applied to a 40-Gbit/s EADFB laser integrated with a short SOA.

We have proposed and developed a new type of electroabsorption modulator (EAM) that employs both optical absorption and interferometric extinction. The EAM operates at a record low voltage of 0.2 V at 25.8-Gbit/s modulation, which can reduce optical transmitter power consumption and allows the adoption of cost-effective CMOS drivers.

High-Speed (400 Gb/s) Eight-Channel EADFB Laser Array Module Using Flip-Chip Interconnection Technique

We have developed a novel electroabsorption modulator (EAM)-integrated distributed feedback laser (EA-DFB laser), in which an EAM functioning as an external modulator is integrated in a Mach-Zehnder interferometer (MZI). The MZI-type EAM (MZEA) modulates light intensity by both optical absorption and interferometric extinction. As a result, it improves the extinction ratio (ER) of a conventional EAM, which allows us to reduce the modulation voltage (Vm ), and thus reduce the power consumption of the driver circuit. A fabricated MZEA-integrated DFB laser (MZEA-DFB laser) exhibited high-ER operation and an output power of about 8 dBm, which is comparable to that of a conventional EA-DFB laser, with a 100-mA laser current. Thanks to the high ER and sufficient output power, the MZEA-DFB laser operating at half the Vm of a conventional EA-DFB laser is able to generate optical signals with a given optical modulation amplitude, and we achieved a 25.8-Gb/s 40-km transmission with the novel laser at a Vm of 1 Vpp.

Very-low-voltage operation of Mach-Zehnder interferometer-type electroabsorption modulator using asymmetric couplers

We developed an InP-based 4x1 transversal filter (TF) with multi-mode interference couplers (MMIs) as a compact wavelength multiplexer (MUX) 1700 μm x 400 μm in size. Furthermore, we converted the MMI-based TF to a reflection type to obtain an ultra-compact MUX of only 900 μm x 50 μm. These MUXs are made with a simple fabrication process and show a satisfactory wavelength filtering operation as MUXs of monolithically integrated light source arrays, for example, for 100G bit Ethernet.

Low Driving Voltage Operation of MZI-Type EA Modulator Integrated With DFB Laser Using Optical Absorption and Interferometric Extinction

We developed a new type of EAM-integrated DFB laser that employs both optical absorption and interferometric extinction. And, we achieve a 25.8-Gbit/s 40Gbit/s 40-km transmission with the km novel laser at a modulation voltage of 1 Vpp.