High power edge-emitting light emitting diodes at 1.5 μm with extremely low back facet feedback

This paper describes novel semiconductor sources for optical low coherence reflectometry (OLCR), a measurement technique for characterizing device and fiber reflections with high sensitivity and high spatial resolution. Lasers and conventional superluminescent LEDs are not suitable for OLCR because strong reflections from the back facets mask weak reflection signals from the device or fiber under test. Even standard edge emitting LEDs (EELEDs) show significant reflections, which have limited the dynamic range of previous measurements. Low source output powers have also limited sensitivity. In order to obtain high power while minimizing internal reflections, a high single pass gain device is required. The record combination of high power and low internal reflections of the InGaAsP EELEDs reported here significantly expands the dynamic range and sensitivity of LED based reflectometry at 1.5 μm. This work also compares the characteristics of quantum well and bulk EELEDs