Mode Rejection Ratio Research Articles

Evaluation of the performance of dual-order mode couplers using optical low-coherence reflectometry

Describes a simple and efficient means of evaluating the performance of deep-ridge dual-order mode couplers, a key component in all-optical Mach-Zehnder wavelength converters. The principal characteristics of these couplers namely, the optimal operation wavelength range and the corresponding mode rejection ratio have been determined for the first time using low-coherence reflectometry measurements performed simultaneously in reflection and transmission modes.

Active biasing of multistage CMOS op-amps for performance enhancement

The technique of active biasing is introduced and applied to a high-gain fully differential two-stage CMOS cascode op-amp, in order to enhance its various performance metrics such as gain, unity gain frequency, common mode and power supply rejection ratios, slew rate and settling time. The improved performance is predicted theoretically and substantiated through circuit simulations.

InGaAs/InP distributed feedback quantum well laser

We describe InGaAs/InP multiquantum well distributed feedback (DFB) lasers with novel properties atrributable to the quantum well based active layer. The low internal loss waveguide and shallow gratings have allowed the fabrication of lasers with a cavity length varying from 0.5 to 2 mm, and corresponding threshold currents of 22 and 100 mA, respectively. A mode rejection ratio as high as 50 dB has been obtained in lasers with one antireflection-coated facet. The long cavity devices exhibit linewidths as low as 600 kHz at a power output of 35 mW. Transmission experiments through 70 km of fiber, at 1.7 Gb/s, showed a dynamic chirp penalty of only 0.25 dB, a factor of 8–10 smaller than in conventional lasers.

Effect of external optical feedback on spectral properties of external cavity semiconductor lasers

The effects of external optical feedback on the spectral properties of single-mode external cavity semiconductor lasers that use a graded-index (GRIN) lens in the optical cavity have been investigated. Mode rejection ratio and intensity drop-out rate of the dominant mode as a function of optical strength have been measured. These measurements show that a laser with a short (160 μm) GRIN-lens external cavity can tolerate optical feedback as large as −20 dB without significant penalty. This minimum optical feedback can be larger when lasers with shorter cavity length are used.