Sampled-grating Distributed Bragg Reflector Research Articles

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.

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.

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 Widely Tunable Transceivers

We present the first monolithic widely tunable 40-Gb/s transceivers. The devices integrate sampled grating distributed Bragg reflector (SG-DBR) lasers, quantum-well electroabsorption modulators (EAM), low-confinement semiconductor optical amplifiers (SOA), and uni-traveling carrier (UTC) photodiodes for state-of-the-art light generation, modulation, amplification, and detection. A relatively simple high-flexibility fabrication scheme combining quantum-well intermixing (QWI) and blanket metal-organic chemical vapor deposition (MOCVD) regrowth was used to integrate components with performance rivaling optimized discrete devices. The SG-DBR/EAM transmitters demonstrate 30 nm of tuning, 39-GHz bandwidth, low-drive voltage, and low power penalty 40-Gb/s transmission through 2.3 km of fiber. The SOA/UTC photodetector receivers provide 23-28 dB of gain, saturation powers up to 18.6 dBm, and -20.2 dBm of chip-coupled sensitivity at 40 Gb/s. By connecting the transmitters and receivers off-chip, we demonstrate 40-Gb/s wavelength conversion

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

Monolithic Wavelength Converters for High-Speed Packet-Switched Optical Networks

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper describes the design and demonstration of advanced 40-Gb/s return-to-zero (RZ) tunable all-optical wavelength converter technologies for use in packet-switched optical networks. The device designs are based on monolithic integration of a delayed interference Mach–Zehnder interferometer (MZI) semiconductor optical amplifier (SOA) wavelength converter with a sampled-grating distributed Bragg reflector tunable laser and an on-chip waveguide delay. Experimental results are presented demonstrating error-free wavelength conversion with 1-dB power penalty at 40-Gb/s data rates. By incorporating label modulation functionality on-chip along with a fast tunable 40-Gb/s wavelength converter, fully monolithic packet-forwarding chips are realized that are capable of simultaneous error-free wavelength conversion of 40-Gb/s payloads, remodulation of 10-Gb/s packet headers, and data routing through fast wavelength switching. </para>

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.

Thermal effects in monolithically integrated tunable laser transmitters

We investigate thermal effects in widely tunable laser transmitters based on an integrated single chip design. The chip contains a sampled-grating distributed Bragg reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption modulator (EAM). The thermal impedance of the ridge structure is evaluated through simulation and experiment, and thermal crosstalk between sections is examined. Heating of the mirrors by neighboring sections is found to result in unintentional offsets in wavelength tuning. Thermal effects in the EAM are examined in depth. A positive feedback mechanism causes local temperature rise at the modulator input, with the potential to trigger catastrophic thermal runaway. A self-consistent finite-element model is developed to simulate the EAM temperature profile and device performance. This model is used to optimize the device, resulting in integrated EAMs that achieve a dissipated power limit in excess of 300mW.

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.

10 Gb/s wavelength conversion using a widely tunable series push-pull photocurrent-driven transmitter

Error-free operation at 10 Gb/s was demonstrated for a hybrid photocurrent-driven series push-pull Mach-Zehnder-based wavelength converter. Back-to-back power penalties of <1 dB for pseudorandom binary sequence (PRBS) 2/sup 7/-1 and <2.3 dB for PRBS 2/sup 31/-1 were measured across the 37-nm wavelength tuning range of the sampled-grating distributed Bragg reflector.

A widely tunable SOA-integrated DBR laser by combination of sampled and superstructure gratings

We report on the development of the first 30 nm tunable laser diode utilizing a front sampled grating-distributed Bragg reflector (SG-DBR) and a rear superstructure grating DBR (SSG-DBR). A high output power greater than 18 mW was achieved with superior longitudinal mode stability, as well as an overall power variation of less than 3 dB for the well-defined laser. Furthermore, lasers integrated with a semiconductor optical amplifier (SOA) enabled the output power to be controlled independently both by the active current and the SOA current, as well as achieving a maximum output power of 45 mW. The side-mode suppression ratio was in excess of 40 dB for all the 50 GHz spaced wavelength channels.

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.

Thermally Controlled Wavelength Locker Integrated in Widely Tunable SGDBR-LD Module

A sampled-grating distributed Bragg reflector laser module having an integrated multiwavelength locker has been developed and evaluated. The uniquely designed wavelength locker made of thermally controlled etalon has provided uniform wavelength monitoring and very stable wavelength locking in the 188-ITU grid channels (37 nm) with 25-GHz spacing. Over the case temperature from -5/spl deg/C to 65/spl deg/C, the laser wavelength was locked within /spl plusmn/0.5 GHz, and the total power consumption of the module was less than 4 W.

Design and Performance of a Monolithically Integrated Widely Tunable All-Optical Wavelength Converter With Independent Phase Control

We report on a new widely tunable all-optical wavelength converter consisting of a sampled-grating distributed Bragg reflector (SGDBR) laser monolithically integrated with a Mach-Zehnder interferometer semiconductor optical amplifier (MZI-SOA)-based wavelength converter. The new design incorporates independent phase control of the interferometer and SOAs for amplification of the SGDBR output. For the first time, error-free operation for data rates of up to 10 Gb/s is reported for 35-nm output tuning range. The high-speed operation is enabled by high photon density in the SOA due to large power transfer from the on-board tunable laser and amplifiers. We also report on device sensitivity of -10 dBm at 2.5 Gb/s and -5 dBm at 10 Gb/s, with an average output power of 0 dBm.

Single-Chip Wavelength Conversion Using a Photocurrent-Driven EAM Integrated With a Widely Tunable Sampled-Grating DBR Laser

Tunable photocurrent-driven wavelength converters using widely tunable sampled grating distributed Bragg reflector lasers, electroabsorption modulators, semiconductor optical amplifiers, and an optically preamplified receiver have been fabricated and tested. Dynamic wavelength conversion has been achieved over 40 nm with optical bandwidths up to 10 GHz.

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