Lewis B. Aronson

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.

A duplex 10 Gb/s serial active optical cable for short-reach applications

Optical links offer many advantages over copper based solutions for 10 Gb/s interconnects, including lighter weight, longer reach and lower power consumption. Copper solutions are either very bulky and of limited reach (10GBASE-CX4) or have high power dissipation (>10W for a 10GBASE-T link). Previous optical solutions for high-volume, short interconnects have been limited by cost and connector cleanliness considerations. In this paper, we describe a duplex active optical cable which overcomes these limitations. Active optical cables not only retain the advantages of optical links with the external characteristics of an electrical cable, but provide additional advantages in performance and yield by eliminating the extra link margins inherent in open optical link standards. A new electrical connector is described which provides excellent return loss performance, high density and a rugged, consumer friendly design. Performance results for 15m graded index plastic optical fiber and 100m multimode glass fiber based cables are reported. Low jitter contribution and power dissipation of ~1W per link are achieved. Finally the design and performance of adapters allowing the use of this cable in present SFP+ and XFP transceiver systems is presented.