Overall Design

A schematic of the overall subsystem diagran in attachment.

RF and Optical Connections

Starting at the top left corner is the diode laser module.  This laser has an input which allows it to be amplitude modulated.  The output of the laser is coupled into an optical fiber which is connectorized with an FC/APC connector and is connected to the input port of a 1 by 16 Optical Fiber Splitter. The Splitter produces 16 optical fiber outputs dividing the input laser power into 16 roughly equal optical optical fiber outputs.  These optical fibers are routed to the Photodiode Receivers (PD) which are the devices under test. All of the PDs are illuminated simultaneously with amplitude modulated light. The Optical Fiber outputs each have a collimating fiber telescope which is used to focus the light onto the PDs. Optical Fiber CH1 is routed to a broadband flat response reference photodiode which is used to provide a reference to the HP-4395A Network Analyzer.  The other Channel outputs are connected to an RF switch which can be programmed to select one of 16 inputs as the output.  The selected outputs can then be sent into channel A of the RF Network Analyzer. 

RF Switch

The RF switch consists of two 8 by 1 Multiplexers (National Instruments PXI-254x) slotted into a PXI Chassis (National Instruments PXI-1033).  The Multiplexers have 8 RF inputs and one RF output and can be programmed through the PXI Chassis to select one and only one of the 8 inputs to be routed to the RF output.) The first 8 Channels are connected to the first 8 inputs of the first Multiplexer.  The first Multiplexer’s output is then connected to the Channel 1 input of the second Multiplexer. The remaining PD outputs are connected to the remaining inputs of the second Multiplexer. The output of the second Multiplexer is connected to the A channel of the RF Network Analyzer.  Thus it is possible to select any one of the PD RF outputs for analysis.

Software

Something on this tomorrow.