Transmitter optical subassembly for XFP applications

Finisar has developed a transmitter optical subassembly based on a TO-can style package with a ceramic feedthrough in place of the traditional kovar pins in glass seals. A copper/tungsten (CuW) heatsink also passes through the header base as a means of transferring heat from inside the hermetic enclosure to the module shell. The subassembly has been built in two versions. The first has a 25-Ohm feedthrough design for direct drive of edge emitting lasers. The second design has a 50-Ohm feedthrough for cooled externally modulated laser (EML) applications. In the latter design, a miniaturized TEC is incorporated between the CuW heatsink and the device submount. Data is presented on electrical modeling and measurements showing a return loss of >14 dB out to 20 GHz. For the direct modulation application, optical eye diagrams show very good overall performance over temperature for 1310nm DFB applications. Data is also presented showing performance distributions over large numbers of parts as well as some reliability test results. For the 1550 nm application, optical eye diagram results are presented along with measured thermal performance data.