|
A high performance edge emitting 830 nm LED has been mated with SMA and ST fiber optic receptacles using an internal lens to achieve performance comparable to a pigtailed device at substantially lower cost. The absence of a pigtail enhances reliability and simplifies handling during PC board assembly. The design goals included -7 dBm minimum launched power into a 100 micron core fiber at 150 mA drive current, compatibility with existing active device packages, electrical isolation of all pins from the package, and 0° to 50°C operation, typical of commercial Local Area Network (LAN) requirements. These objectives are attained using a cylindrical Graded Index (GRIN) lens bonded into the package, and active alignment of the device during assembly. Where the highest power is required, as in passive star LANs, coupled powers of -3 dBm are easily achieved at 150 mA; alternatively, optical power can be traded for reduced drive current, an attractive property for active star based LANs. The devices exhibit rise times of 4 to 7 ns, with 2 ns available at reduced power output. Repeatability of coupled power for multiple connections of the same or different 100 micron core fibers is typically ±0.5 dB for SMA Type 2 connectors, and ±0.25 dB or less for SMA Type 1 and ST connectors. The devices withstand ten thermal shock cycles (-40° to + 100°C) with no significant change in optical output. Accelerated life testing has demonstrated a MTTF of 2.7 x 107 hours for unpackaged devices, and preliminary results indicate comparable lifetimes for the packaged devices. The paper will discuss the design criteria for optimum coupling in a system consisting of an edge emitting LED, GRIN lens, and connectorized optical fiber; comparison to other lens systems will be made. Data for coupled power versus drive current and fiber size (100 micron, 62.5 micron, 50 micron) will be presented. In addition, results of high pulsed current operation will be given.
|
