The recent activity in transceiver and transponder multi-source agreements has led to smaller, cost efficient modules to
enable telecom and datacom systems in many different applications. At data rates of 10Gb/sec these applications can be
include transmission distances < 100m or greater than 80km. The transmitter optical engines which go into these
products must meet many constraints in terms of performance, cost, size and manufacturability. This paper will identify
some of the key design issues engineers must address and potential solutions for those issues.
High power buried heterostructure 1.55micrometers tunable DBR lasers have been designed, fabricated and characterized. The laser consists of a gain section, a distributed Bragg reflector, a semiconductor optical amplifier and front photodetector for automated power control. The heterostructures were grown by MOCVD with the help of selective area growth techniques and dual waveguide heterostructure. Several advantages stem from this integration scheme which include simplicity of design and fabrication, increased reliability and low cost. The laser exhibits output power of 13dBm in the fiber and is tunable over 30(50GHz) ITU channels. The laser exhibits excellent performance and long-term control and reliability. The laser/transmitter also demonstrates significant increase of its functionality while its size remains small.
Tunable lasers are becoming critical in DWDM systems for reasons of increased system functionality, system adaptability and costs. Key issues that arise are wavelength tuning range, characterization of the devices, wavelength control, mode stabilization, wavelength switching times, output power and long term stability of operation. We have developed tunable EML components and transmitters that address all these issues. Transmission at 2.5 Gb/sec over 640 km of fiber has been demonstrated using an EA-DBR capable of being tuned to any one of 20 wavelengths spaced at 50 GHz. These lasers are integrated into a single package with wavelength stabilization elements and can be stabilized such that both the desired wavelength and mode are maintained during operation. These integrated modules are also incorporated into a small form factor transmitter capable of operating in DWDM systems.
Proc. SPIE. 2547, Laser Techniques for Surface Science II
KEYWORDS: Quantum wells, Diffusion, Electroluminescence, Near field scanning optical microscopy, Near field, Surface properties, Laser damage threshold, Spatial resolution, Laser optics, Near field optics
Near-field scattering optical microscopy (NSOM) is used to characterize the emission output and to obtain photoconductivity maps of InGaAsP multiple quantum well lasers. The high spatial resolution of NSOM (approximately (lambda) /20) allows detailed imaging of the laser structure. Emission measurements not only provide direct visualization of the laser mode but also reveal unwanted emission due to InP electroluminescence. Near-field photoconductivity experiments yield high resolution measurement of carrier transport throughout the structure yielding valuable information on current leakage, defect formation, and the quality of p-n junctions.