We demonstrate the high-speed operation of a wavelength- division-multiplexed optical interconnect, which is implemented by multiplexing the optical data from a multiple wavelength vertical-cavity surface-emitting laser (VCSEL) array into a single optical fiber, and demultiplexing the composite data stream using an array of resonance-enhanced photodetectors (REPD) with matching resonance wavelengths. By using VCSELs and REPDs with a quasi-planar oxide- confinement design for improved high speed performance, and using strained InGaAs/GaAs quantum wells to achieve a better trade-off between optical responsivity and wavelength selectivity, WDM operation has ben demonstrated under 1.25 Gb/s data modulation, with an optical crosstalk rejection ratio of better than -10 dB for wavelength channels that are spaced approximately 4 nm apart. The transmission performance of a single-channel, 1.0 Gb/s fiberoptic link with a 1 km span is characterized, achieving a BER equals 10-12 at a received optical signal level of -16.7 dBm. In addition, the effect of optical crosstalk from a neighboring wavelength channel, as well as the power penalty for thermally-induced wavelength de-tuning between the VCSEL and REPD have been determined.
Monolithic multiple-wavelength arrays of vertical-cavity surface-emitting lasers (VCSEL) and resonance-enhanced photodetectors (REPD) with matching wavelengths are useful for wavelength-division multiplexed optical interconnects, in which parallelism is achieved using a single fiber. Multiple wavelength channels can be optically multiplexed and broadcast to different nodes, where they are demultiplexed (selected) by REPDs with different spectral selectivity. Alternatively, the multiplexed data can be spectrally separated and sent to different destinations. Wavelength-graded VCSEL arrays with a 57 nm wavelength span have been realized, and VCSELs have been integrated with REPD arrays for improved wavelength matching. Wavelength multiplexing and demultiplexing are demonstrated at > 1 Gb/s using quasi-planar, multi-wavelength, InGaAs (VCSEL) and REPD arrays with closely matching wavelengths, with a crosstalk of > 10 dB between channels approximately 4 nm apart. The transmission performance of a single-channel fiberoptic link with a 1 km span is characterized, and the impact of optical crosstalk from neighboring wavelength channels and the effect of thermally-induced wavelength de- tuning are studied.
Monolithic wavelength-graded vertical-cavity surface- emitting laser (VCSEL) and wavelength-selective resonance enhanced photodetector (REPD) arrays have been developed for use in wavelength-division multiplexed optical interconnect architectures. The aim is to achieve a cost-effective wavelength-multiplexed optical interconnect that can carry a large amount of data over longer distances using a single optical fiber. A controllable means for producing wavelength-graded VCSEL and REPD arrays is described, based on the topography-controlled MOCVD growth on a patterned substrate. This technique allows the growth rate of all the epilayers to be scaled, thereby providing closer tracking of the reflectance peak and the gain peak and resulting in more uniform device characteristics. VCSELs and REPDs have been monolithically integrated using the same epilayer structure and the same growth technique. This paper focuses on (1) the characteristics of oxide-confined multi-wavelength VCSEL arrays, (2) the design and comparison of optimized REPD structures at 850 nm and at 980 nm, and (3) wavelength multiplexing and demultiplexing using VCSEL and REPD arrays.
Monolithic, uniformly-wavelength-graded, vertical-cavity surface- emitting laser (VCSEL) and wavelength-selective resonance- enhanced photodetector (REPD) arrays are key enabling technologies for many wavelength-multiplexed optical network and interconnect architectures. These arrays can be produced in a repeatable and uniform manner by controlling the local MOCVD growth rate of the epilayers on a topographically patterned substrate, which resulted in wavelength-differentiated devices with more uniform optical characteristics. Multi-wavelength VCSEL and REPD arrays have been monolithically integrated on the same substrate to improve the wavelength matching between the source and detector elements. The performance characteristics of these arrays are discussed. We also describe a wavelength-division- multiplexing and demultiplexing experiment in which several channels of optical data are multiplexed together using a multi- wavelength VCSEL array and transmitted on a single optical fiber, and are demultiplexed at the other end using a wavelength- selective REPD array with closely-matching wavelengths.
Monolithic, multiple-wavelength VCSEL arrays have been obtained by using the surface-controlled enhancement and reduction of the MOCVD epitaxial growth rate to produce a periodic and repeatable grading of the resonance wavelength over a span of greater than 30 nm. Room temperature, electrically-injected, cw lasing has also been achieved with a wavelength span of greater than 20 nm. We show here both the enhancement and the reduction of the growth rate of the entire VCSEL structure and demonstrate the controlled variation of the VCSEL lasing wavelength over a widened spectral range by exploiting both of these effects. Using the same growth techniques, wavelength-selective, resonance-enhanced photodetector arrays with closely-matched resonance wavelengths can be monolithically integrated on the same epilayer structure. We demonstrate the repeatability of this technique using different arrays from the same growth run.
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