Optical transceiver module for star networks in cars

摘要

Here we present an optical transceiver concept for a reflective star bus system, showing favorable properties in respect to coupling efficiency and packaging. It is based on a hot embossed polymer substrate with two integrated micro-mirrors and a waveguide. On top of the substrate, above the mirrors, a vertical-cavity surface-emitting laser diode (VCSEL) and a photodiode chip are mounted with a flip-chip technique. At the end face of the waveguide a Polymer Clad Silica (PCS) fiber with a core diameter of 200 μm is attached in a groove. Thus an easy assembly of the individual components and a compact package is achieved. To evaluate and optimize the efficiency of the transceiver module we performed extended ray tracing calculations. Included are coupling efficiency between fiber and planner waveguide as well as coupling efficiencies between VCSEL and waveguide and between waveguide and photodiode, respectively. For a realistic estimation we took the transverse mode emission behavior of VCSELs at different supply currents and temperatures into account. Therefore we measured far-fields of VCSEL chips mounted on a heat sink for temperatures up to 85 °C and included the results in the simulations. The calculations indicate that the temperature dependant output and included the results in the simulations. The calculations indicate that the temperature dependant output power of the VCSEL is partly compensated by the variation in coupling efficiency. Measured VCSEL to fiber coupling efficiencies of about 60% and out-coupling efficiencies to the photodiode of 70% are achieved, in good agreement with calculations. Therefore our compact and low-cost concept shows at least 2 dB lower insertion losses compared to conventional 3 dB coupler solutions.