Ken Tsuzuki

Design and Fabrication of 10-/40-Gb/s, Uncooled Electroabsorption Modulator Integrated DFB Laser With Butt-Joint Structure

This paper describes the wide temperature range operation of an electroabsorption modulator (EAM) integrated with DFB laser diodes (LDs) (EML) designed to reduce the power consumption and size of optical transmitters. We optimized the multiquantum wells (MQWs) for LD and EAM separately to realize uncooled operation. We employed a conduction band offset (¿Ec) of around 250 meV for the LD and 150 meV for the EAM. The number of well layers was set at 6 for the LD and 12 for the EAM, respectively. We fabricated the EML using a butt-joint (BJ) process to allow us to design the LD and the EAM independently. We introduced a ridge waveguide structure for the LD and EAM waveguides, and designed the width of the LD and EAM mesa to achieve a high optical coupling efficiency between the LD and the EAM. We then used the 200-¿ m-long EAM for 10-Gb/s operation and the 150- ¿m-long EAM for 40-Gb/s operation, and thus obtained a dynamic extinction ratio of over 9 dB at 10 Gb/s from -25 °C to 100 °C and of 8.2 dB at 40 Gb/s from -15 to 80°C. We achieved a power penalty of less than 2 dB after an 80-km single-mode fiber (SMF) transmission at 10 Gb/s and a 2-km SMF transmission at 40 Gb/s over a wide temperature range. These results confirm the suitability of this EML with a BJ structure for use as a 10-Gb/s or 40-Gb/s uncooled light source.

A 40-gb/s InGaAlAs-InAlAs MQW n-i-n Mach-Zehnder Modulator with a drive Voltage of 2.3 V

We have developed a traveling-wave Mach-Zehnder modulator using an n-i-n heterostructure fabricated on an InP substrate. We obtained an extremely small /spl pi/ voltage (V/spl pi/) of 2.2 V, even for a short signal-electrode length of 3 mm. We confirmed that the device has an impedance-matched electrode and operates at 40 Gb/s with a single-ended drive voltage of 2.3 V.

NRZ operation at 40 Gb/s of a compact module containing an MQW electroabsorption modulator integrated with a DFB laser

NRZ operation at 40 Gb/s has been successfully performed using a very compact module of a multiple-quantum-well (MQW) electroabsorption modulator integrated with a distributed-feedback (DFB) laser. While the DFB laser is injected with a constant current, the integrated MQW electroabsorption modulator is driven with a 10-Gb/s electrical NRZ signal. A clearly opened eye diagram has been observed in the modulated light from the modulator. And a receiver sensitivity of -27.2 dBm at 10/sup -9/ has been experimentally confirmed in the bit-error-rate (BER) performance.

80-Gb/s Low-Driving-Voltage InP DQPSK Modulator With an n-p-i-n Structure

We present a traveling-wave-electrode InP-based differential quadrature phase-shift keying modulator with a novel n-p-i-n waveguide structure. The structure features low electrical and optical propagation losses, which allow the modulator to operate at a high bit rate together with a low driving voltage and a low insertion loss. We successfully demonstrate 80-Gb/s modulation with a driving voltage of only 3 Vpp in a push-pull configuration. The chip size is just 7.5 mm times 1.3 mm.

Wide Temperature Range Operation of a 1.55-

We present the uncooled operation of a 1.55- mum 40-Gb/s InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser within a temperature range of 95degC (-15degC to 80degC ). To the best of our knowledge, this is the largest temperature range reported so far for such a 40-Gb/s EAM integrated DFB laser. We designed the EAM to operate at high speed by reducing the electrical parasitics, and we achieved a 3-dB frequency bandwidth of over 39 GHz for an EAM length of less than 150 mum. We demonstrated a 2-km single-mode fiber (SMF) transmission at 40-Gb/s over a wide temperature range of -15degC to 80degC by adjusting only the bias voltage to the EAM while keeping the modulation voltage swing constant at 2.0 V when the temperature changed. We achieved a dynamic extinction ratio of over 8.2 dB and a 2-km SMF transmission with a power penalty of less than 2 dB over a wide temperature range.

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We demonstrate 1.04-Tbit/s (13-channel) dense-WDM transmission experiment based on alternate-polarization 80-Gbit/s signals with 0.4-bit/s/Hz spectrum efficiency, over a 89-km zero-dispersion-flattened transmission line using a Mach-Zehnder modulator pulse generator.

m 40-Gb/s Electroabsorption Modulator Integrated DFB Laser for Very Short-Reach Applications

We fabricated a compact 10-Gb/s-wavelength tunable laser module by integrating a tunable DFB laser array and an InP-based n-i-n Mach-Zehnder modulator in one package. We developed a multichip assembly technology to realize high optical coupling efficiency and achieved a continuous-wave output power of +6.5 dBm. We demonstrated a full C-band 10-Gb/s optical duobinary transmission with a constant modulation voltage of 2.4 Vpp. And we achieved a 200-km single-mode-fiber transmission with a power penalty of less than 1.0 dB over the entire C-band range.

1.04-Tbit/s DWDM transmission experiment based on alternate-polarization 80-Gbit/s OTDM signals

A widely-tunable DFB-laser array module operating in the L-band is developed. It can cover a wide range (3.15 THz) with a high SMSR (>45 dB). A fiber-output power of 40 mW and high-speed switching are achieved by LD current tuning.

Full C-Band Tunable DFB Laser Array Copackaged With InP Mach–Zehnder Modulator for DWDM Optical Communication Systems

A compact wavelength tunable laser module is fabricated by integrating a wavelength tunable laser array and an n-i-n structure Mach-Zehnder modulator. Without the need to change the driving condition of the Mach-Zehnder modulator, the module can operate at 10 Gb/s in the 32 nm C-band range.

High-power (40 mW) L-band tunable DFB laser array module using current tuning

We have developed a four-channel 10-Gb/s electroabsorption modulator array. We have introduced an innovative technique with an impedance-matched film (IPF) carrier to feed the electrical driving signal. The IPF carrier is made of an insulating polyimide film on which a coplanar waveguide is formed. We have achieved 10-Gb/s operation for all channels with clear eye opening and with negligibly small crosstalk. Polarization independence is confirmed for each arrayed channel.