Sampled-grating Distributed Bragg Reflector Laser Research Articles

Effects of the electrical signals generated in passive sections of SG-DBR lasers

We investigate electrical signals generated in passive sections of a sampled-grating distributed Bragg reflector laser. A DC voltage is applied to one of the passive sections, and a negative current in the circuit is observed with a low voltage biased. Experimental results demonstrate that the negative current is generated due to photovoltaic effect. This effect could be enhanced or suppressed by adjusting the parameters of p–n junctions in the passive sections. On account of this effect, the passive sections can be utilized as inner photodetectors to control the laser power, which greatly simplifies the laser packaging and reduces the cost.

Fast and precise control for improved dynamic performance of a sampled grating distributed Bragg reflector laser integrated with semiconductor optical amplifier

We demonstrate fast power and wavelength control of a monolithic sampled grating distributed Bragg reflector (SGDBR) laser integrated with semiconductor optical amplifier (SOA). Optical power leveling for different channels can be achieved by tuning SOA driving current. Wavelength switching transients are analyzed experimentally. An appropriate shuttering operation of SOA sections during the channel switching process is implemented to eliminate the impact of transient emitting modes, and greatly improved dynamic performance of the SGDBR laser can be observed. With our design, output power of the laser can be precisely controlled within 0.1 dB and rapidly shuttered within 2 ns.

An 8$\,\times\,$8 InP Monolithic Tunable Optical Router (MOTOR) Packet Forwarding Chip

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we demonstrate single-channel operation of the first InP monolithic tunable optical router (MOTOR) chip designed to function as the packet forwarding engine of an all-optical router. The device has eight-input and eight-output ports and is capable of 40-Gb/s operation per port with bit-error rates below 1E-9. MOTOR integrates eight wavelength-tunable differential Mach–Zehnder semiconductor optical amplifier (SOA) wavelength converters with preamplifiers and a passive 8<formula formulatype="inline"><tex Notation="TeX">$\,\times\,$</tex> </formula>8 arrayed-waveguide grating router. Each wavelength converter employs a widely tunable sampled-grating distributed Bragg reflector (DBR) laser for efficient wavelength switching across the C band and other functions required for 40-Gb/s wavelength conversion. Active and passive regions of the chip are defined through a robust quantum well intermixing process to optimize the gain in the wavelength converters and minimize the propagation losses in passive sections of the chip. The device is one of the most complex photonic integrated circuits (PICs) reported to date, with dimensions of 4.25 mm<formula formulatype="inline"><tex Notation="TeX">$\,\times\,$</tex></formula>14.5 mm and more than 200 functional elements integrated on-chip. We demonstrate single-channel wavelength conversion and channel switching with this device using <formula formulatype="inline"><tex Notation="TeX">$2^{31}-1$</tex></formula> pseudorandom bit sequence (PRBS) data at 40 Gb/s. A power penalty as low as 4.5 dB was achieved with less than 2-W drive power per channel. </para>

Investigation on wavelength switching of widely tunable SGDBR lasers

The sampled-grating distributed Bragg reflector (SGDBR) laser is a typical and important photonic integrated device, and has potential wide application to agile optical networks. A new dynamic model for this device has been developed, which combines the traveling-wave method for the active region and the transfer-matrix method for the passive sections into a single procedure. The behaviors of wavelength switching of the SGDBR laser, which include the transient spectrum and mode competition, have been studied in detail using this model. A new efficient way has been proposed to improve the wavelength switching performance only by increasing the coupling coefficients without changing the carrier density.

Modeling Widely Tunable Sampled-Grating DBR Lasers Using Traveling-Wave Model With Digital Filter Approach

A theoretical model for simulating widely tunable sampled-grating distributed Bragg reflector (SGDBR) lasers has been developed. The model integrates both time-domain traveling-wave method and frequency-domain transfer-matrix method into a single procedure. The active region of the device is still operated in the conventional time domain, while the passive parts are firstly performed by the transfer-matrix method and then transformed to the time domain via digital filters. Both the static and dynamic characteristics of SGDBR lasers, such as L-I curve, output spectrum, tuning characteristics, large-signal modulation, and dynamic wavelength switching, can be clearly visible in our model and in qualitative agreement with the published experimental results.

A Fast Optical Wavelength-Tunable Transmitter With a Linear Thermoelectric Cooler Driver

This letter demonstrates a fast optical wavelength-tunable transmitter based on a sampled grating distributed Bragg reflector (SG-DBR) laser. A high-precision clock distributing circuit has been introduced into the transmitter to guarantee the switching synchronization for driving currents to different tuning sections of the SG-DBR laser. To achieve fast and accurate wavelength switching, a linear thermoelectric cooler driver board has been applied as a part of the transmitter to stabilize the temperature of the SG-DBR laser. Experiments have been performed to show the wavelength switching characteristics of the optical transmitter.

Modeling Wavelength Switching of Widely Tunable Sampled-Grating DBR Lasers Using Traveling-Wave Model With Digital Filter Approach

A dynamic theoretical model has been proposed for simulating the wavelength switching performance of widely tunable sampled-grating distributed Bragg reflector lasers. The active region of the device is still operated in time domain while the passive parts are first modeled by transfer-matrix method and then transformed into the time domain via digital filter approach. The switching performance and corresponding mode-competition behaviors can be clearly demonstrated by the transient spectrum traced by the switching time.

Improving the Performance of Sampled-Grating DBR Laser-Based Analog Optical Transmitters

In this paper, the available analog link performance of integrated transmitters containing a sampled-grating distributed Bragg reflector laser, a semiconductor optical amplifier, and a modulator is evaluated. It is found that to provide a link gain and a low-noise figure, an RF preamplifier is required, and for this reason, spurious-free dynamic range (SFDR) including a preamplifier has been evaluated. An SFDR of 110-dBHz2/3, a noise figure of 5.4 dB, and link gain of 6.9 dB at 5 GHz is obtained. It is further investigated how link SFDR can be improved by linearization techniques. Two novel approaches are proposed and demonstrated: first, predistortion by extraction of nonlinear components from an integrated second modulator exposed to the same wavelength, optical power and temperature for matched nonlinear terms; second, a novel linearized modulator configuration balancing electroabsorption and Mach-Zehnder modulation that can reach a null for both second- and third-order intermodulation products at a single bias point.

Characterization of Frequency Drift of Sampled-Grating DBR Laser Module Under Direct Modulation

The authors demonstrate the drift in frequency of a static sampled-grating distributed Bragg reflector (SG DBR) laser module when it is subjected to direct modulation. The magnitude of drift and its settling time is characterized as a function of the index of modulation. Results show that when the directly modulated SG DBR is optically filtered, as in a dense wavelength-division-multiplexed system, a power penalty of 6.7 dB is incurred in comparison to the unfiltered case.

Separate Absorption and Modulation Mach-Zehnder Wavelength Converter

A monolithic separate absorption and moduation region (SAM) wavelength converter is demonstrated. The transmitter consists of a sampled-grating DBR (SGDBR) laser and a series-push-pull Mach-Zehnder modulator. The preamplified receiver is composed of a flared semiconductor optical amplifier and a quantum-well pin photodetector. Integrated resistors and capacitors are used to minimize microwave losses and remove the need for external bias tees. The design, fabrication, and operation of this photonic integrated circuit is presented. Small-signal response measurements show a device bandwidth in excess of 20 GHz. Operation at 40 Gbps with NRZ data shows less than a 2.5-dB power penalty across the 32-nm laser tuning range with no additional power penalty for conversion to the input wavelength.

A Monolithic All-Optical Push–Pull Wavelength Converter

We present the first two-stage all-optical push-pull wavelength converter, which has been monolithically integrated in indium phosphide, using an offset quantum-well platform. The device incorporates two cascaded wavelength converters, each with an integrated tunable sampled-grating distributed Bragg reflector laser, and deeply etched total internal reflection mirrors for a compact layout. The device, under push-pull operation, is demonstrated to reduce converted signal pattern dependence at 10 Gb/s, while providing improved phase swing compared to previous offset quantum-well designs. The device is shown to achieve full pi phase swing in the second-stage wavelength converter over a 12-dB input power range.

Design and Operation of a Monolithically Integrated Two-Stage Tunable All-Optical Wavelength Converter

We report on the design and testing of a novel two-stage wavelength-converter architecture, monolithically fabricated in indium phosphide. Two widely tunable integrated sampled-grating distributed Bragg reflector lasers are utilized on chip as probes in both converter stages. The architecture provides a first-stage tunable signal that is internal to the chip (lambdainternal), facilitating cascaded integration of wavelength-sensitive structures, or allowing wavelength conversion for cases where the input wavelength is equal to the output wavelength (lambdainput = lambdaoutput). Output wavelength tuning over 35 nm is shown, and error-free wavelength conversion for lambdainput = lambdaoutput is demonstrated for four wavelengths over a 20-nm range at 2.5 Gb/s. Dynamic range measurements show less than 2 dB of power penalty over a 15-dB variation in input power.

Rapid, Precise, and Stable Control of Optical Frequency for SG-DBR LD Using Quartz Etalon

This paper presents rapid, precise, and stable control of optical frequency for sampled-grating distributed Bragg reflector (SG-DBR) laser diode (LD) using a Z-cut quartz etalon supported at the middle point. The optical frequency of SG-DBR LD was controlled by the mode-hop-free three-electrode control method. As a result, stable mode operation and wide continuous tuning range without mode hopping have been realized. A 0.2-ms optical frequency tuning speed with a 4.35-THz tuning range and a 130-MHz control error of the optical frequency was demonstrated. A 1.1-MHz Allan deviation was reached at an integration time of 12 times 103 s.

40-Gb/s Widely Tunable Low-Drive-Voltage Electroabsorption-Modulated Transmitters

We present the first 40-Gb/s widely tunable electroabsorption modulator (EAM)-based transmitters. The sampled-grating Distributed Bragg Reflector (SG-DBR) laser/EAM devices were fabricated using a multiple-band-edge-quantum-well-intermixing (QWI) technique, which requires only simple blanket regrowth and avoids disruption of the axial waveguide. Devices were fabricated from two different multiple quantum well (MQW) active-region designs for direct comparison. The SG-DBR lasers demonstrated 30 nm of tuning with output powers up to 35 mW. The integrated QW EAMs provided 3-dB optical modulation bandwidths in the 35-39 GHz range, low-drive voltage (1.0-1.5 VPtoP), and low/negative-chirp operation. Bit-error-rate measurements at 40 Gb/s demonstrated 0.2-1.1 dB of power penalty for transmission through 2.3 km of standard fiber

Widely tunable 10 Gbit/s separate absorption and modulation Mach-Zehnder wavelength converter

A fully monolithic separate absorption and modulation region wavelength converter requiring no bias tees has been fabricated. The device consists of a transmitter comprising a sampled-grating DBR laser and series-push-pull Mach-Zehnder modulator, and a receiver composed of a linear semiconductor optical amplifier and a quantum well pin photodetector. The wavelength converter has a 13 GHz bandwidth and demonstrates error-free operation at 10 Gbit/s with unity gain.

40-Gb/s Series-Push-Pull Mach–Zehnder Transmitter on a Dual-Quantum-Well Integration Platform

A series-push-pull Mach-Zehnder modulator is integrated with a sampled-grating distributed Bragg reflector laser on a dual-quantum-well integration platform. The device exhibited greater than 7.8-dB extinction at 40 Gb/s with a 2.5-V drive voltage across a wavelength range of 1541-1566 nm. Bit-error-rate measurements at 10 Gb/s showed error-free operation and negative chirp

Less than 5-ns wavelength switching with an SG-DBR laser

We achieve fast wavelength switching between all channel combinations of a 64-channel sampled-grating distributed Bragg reflector laser in less than 5 ns. The laser was designed to have low tuning currents and efficient heat extraction in order to reduce parasitic thermal effects. We also report on the behavior of the front and back mirror pre-emphasis amplitudes required for the fast switching.

Performance optimization of an InP-based widely tunable all-optical wavelength converter operating at 40 Gb/s

We report on the design and performance optimization of a quantum-well active region-based semiconductor optical amplifier Mach-Zehnder interferometer wavelength converter monolithically integrated with a widely tunable sampled-grating distributed Bragg reflector laser, operating differentially at 40 Gb/s. The device is fabricated using an offset quantum-well platform, requiring a single regrowth. We show error-free operation, with a less than 3-dB power penalty at the optimal differential delay, and open eyes across a 25-nm output tuning range.

Fabrication of Butt-Coupled SGDBR Laser Integrated with Semiconductor Optical Amplifier Having a Lateral Tapered Waveguide

We have demonstrated a high-power widely tunable sampled grating distributed Bragg reflector (SGDBR) laser integrated monolithically with a semiconductor optical amplifier (SOA) having a lateral tapered waveguide, which is the first to emit a fiber-coupled output power of more than 10 dBm using a planar buried heterostructure (PBH). The output facet reflectivity of the integrated SOA using a lateral tapered waveguide and two-layer AR coating of TiO2 and SiO2 was lower than 3 × 10−4 over a wide bandwidth of 85 nm. The spectra of 40 channels spaced by 50 GHz within the tuning range of 33 nm were obtained by a precise control of SG and phase control currents. A side-mode suppression ratio of more than 35 dB was obtained in the whole tuning range. Fiber-coupled output power of more than 11 dBm and an output power variation of less than 1 dB were obtained for the whole tuning range.

40-GHz dual-mode-locked widely tunable sampled-grating DBR laser

Generation of 40-GHz alternate-phase pulses is demonstrated using a dual-mode-locked sampled-grating distributed Bragg reflector laser. More than 10-dB extinction and >20-dB sidemode suppression ratio is measured over the >40-nm tuning range of the laser. Based on captured phase noise spectra, the timing jitter is estimated in the 0.35-0.41-ps range. The demonstrated dual-mode laser would form an attractive basis for an integrated 40-Gb/s return-to-zero transmitter.