The 35PD300-ST, an InGaAs photodiode with a 300mm- iameter photosensitive region packaged in a TO-46 header and actively aligned in an AT&T ST active device mount, is designed for applications in both moderate-bit-rate fiberoptic communications and high sensitivity test and measurement equipment. This device is one of the most versatile of the Telcom Devices™ family of optoelectronic components. Planar semiconductor design and dielectric passivation provide for superior performance. Reliability is assured by hermetic sealing and a 100% purge burn-in (200oC, 15 hours, Vr = 15V). Devices with enhanced responsivity at 850nm are available.