This part is a kind of semiconductor called AMT128503.

Function of this product has 1.25Gb/s Integrated 850nm MSM-TIA.

Manufacturers : ANADIGICS Inc

Image and pinout :

Some of the text within the PDF file :

1.25 Gb/s Integrated 850 nm MSM-TIA AMT128502A Data sheet - Rev. 0 FEATURES · 1.25 Gb/s Differential Output TIA · 5V Operation · Automatic Gain Control · 850nm Photodetector with 100 mm x 100 mm Active Area · Integrated MSM detector & TIA · TO-46 Ultra Flat Window APPLICATIONS · · Gigabit Ethernet (1.250Gb/s) Fibre Channel (1.0625 Gb/s) T46F TO-46 Ultra Flat Window Package Product Description The ANADIGICS AMT128502A is a 5V monolithically integrated Metal-Semiconductor-Metal (MSM) photodetector and transimpedance amplifier (TIA) used to convert an 850nm input optical signal into a differential output voltage, and is manufactured in ANADIGICS’ 6” GaAs wafer fabrication facility. The integrated MSM and TIA receiver maximizes the receiver performance by minimizing the photodete [ ... ]

AMT128503 PDF Datasheet Download