Charles W. Lentz

40-Gb/s tandem electroabsorption modulator

In this letter, we have developed a tandem electroabsorption modulator with an integrated semiconductor optical amplifier that is capable of both nonreturn-to-zero and return-to-zero (RZ) data transmission at 40 Gb/s. The tandem modulator consists of a broad-band data encoder and a narrow-band pulse carver. The pulse carver is able to produce 5-ps pulses with more than 20 dB of extinction. The on-chip semiconductor optical amplifier provides up to 8.5 dB of fiber-to-fiber gain and enables the modulator to be operated with zero insertion loss. Devices have been realized with greater than 40-GHz bandwidth, and 13-dB dynamic extinction for a 2.5-V swing. For optimized designs bandwidths of nearly 60 GHz: have been realized. Using these devices penalty free RZ data transmission over a 100-kin dispersion compensated fiber link has been demonstrated with a received power sensitivity of -29 dBm.

40 Gb/s tandem electro-absorption modulator

NRZ and RZ data transmission at 40 Gb/s are demonstrated for the first time using buried heterostructure tandem electro-absorption modulators monolithically integrated with a semiconductor optical amplifier and input/output spot-size converters. Zero penalty RZ transmission over a 100 km dispersion managed link is achieved.

40 Gb/s photonic integrated receiver with -17 dBm sensitivity

We report on the design, fabrication and characterization of a novel 40 Gb/s optical receiver. The device consists of a high-speed waveguide photodiode monolithically integrated with a semiconductor optical amplifier to create a fully photonic receiver. We have achieved a back-to-back receiver sensitivity of -17 dBm for NRZ data transmission at 40 Gb/s. When used with an erbium doped fiber preamplifier a sensitivity of -32 dBm or 123 photons/bit has been realized for RZ transmission with -6 dBm input power at the receiver. The device has a small signal bandwidth of 39 GHz and a conversion gain of more than 800 Volts per Watt.

3.2 Tbit/s (40 /spl times/ 80 Gb/s) transmission over 1000 km with 100 km span (25 dB loss) and 0.8 bit/s/Hz of spectral efficiency

We demonstrated 3.2 Tb/s (40 ch /spl times/ 80 Gb/s) signal transmission over 1,000 km of TrueWave-RS fiber with 100 km span (25 dB loss) by the use of newly developed tandem electroabsorption modulators, LiNbO/sub 3/ modulators, hybrid Raman/EDFA, dynamic gain equaliser filters, and passive filtering to suppress the linear cross talk. An optimum dispersion map was incorporated to further relax the nonlinearity based impairment on the system.

40Gb/s tandem electro-absorption modulator

NRZ and RZ data transmission at 40Gb/s are demonstrated for the first time using buried heterostructure tandem electro-absorption modulators monolithically integrated with a semiconductor optical amplifier and input/output spot-size converters. Zero penalty RZ transmission over a 100km dispersion managed link is achieved.

Integrated photonic devices for fiber optic communication systems

Fabrication and epitaxial growth technology for III-V semiconductor devices have developed to the point where substantial levels of photonic integration are now feasible. Both highly complex and simple photonic integrated devices are currently the subjects of much active research and product development. These efforts are motivated by the many potential advantages of photonic integration, reduced size, lower power consumption, increased functionality, higher performance and above all else lower cost. We discuss two different examples of photonic integrated devices that demonstrate some of the significant performance advantages that can be achieved with this technology. Both devices are fabricated using our deep ridge buried heterostructure technology that combines both SAG and butt joint epitaxial techniques to obtain the maximum flexibility in the device design. The first device is a high-speed modulator with an integrated phase shifter that enables the transmitter chirp to be dynamically tuned. This enables the transmission performance to be optimized for different amounts of fiber dispersion. In this device the phase shifter can be driven either with a synchronous sinusoidal source or a complementary data modulation. By varying either the amplitude of the drive signal or the bias on the phase modulator the chirp of the transmitted optical pulses can be controlled. For synchronous sinusoidal or narrowband chirp control a single frequency drive signal synchronized with the data modulation is applied to the phase modulator. This signal can be used to apply either positive or negative chirp to the transmitted data bits by varying the phase and amplitude of the drive signal. A more sophisticated approach uses the complement of the data modulation signal to drive the phase modulator. This method referred to as broadband chirp control provides better compensation since it applies frequency chirp only to the transitions in the signal.

40-Gb/s electroabsorption-modulated NRZ and RZ sources

Electro-absorption modulated sources are likely to be key components in the evolution of optical communication line rates from 10Gb/s to 40 Gb/s. Compared with the LiNbO3 alternative EA modulators are more compact, less expensive, compatible with monolithic integration, and offer lower drive voltages. However, fabrication complexity and open questions concerning the fidelity with which they transmit information make the exact role of 40Gb/s EA modulators in advanced communication systems somewhat unclear. In this talk we will describe the design, fabrication and transmission performance of 40Gb/s EA modulators configured for both NRZ and RZ operation. For NRZ transmission the device structure consists of a short MQW modulator with spot-size converters on the input and output ends. Tandem EA modulators for pulse carver and data encoder functions were monolithically integrated along with a semiconductor optical amplifier and input/output spot-size converters to explore RZ transmission. Both single and tandem modulator design are realized using semi-insulting InP current confined buried heterostructure technology. Modulation bandwidth of better than 50 GHz is demonstrated along with a fiber-to-fiber insertion loss of less than 6 dB for the single modulator design. The carver/encoder configuration with onboard SOA yields better than 0 dB insertion loss. Transmission impairments were studies using both designs.