N4917A Optical Receiver Stress Test Solution v 1.3

Optical Receiver Stress Test

The calibrated optical receiver stress test solution provides accurate signal stress for receiver tolerance and compliance testing. It is available for the popular standards of 10 Gb Ethernet IEEE 802.3ae for -LR, -ER, -SR, and for 8G and 10G Fibre Channel. The parameters of ER, OMA, SI and PJ are calibrated and can be dialed so VECP and total jitter are be precisely set.

The stress signal is generated from the J-BERT N4903B with help of the N4917A-E01 receiver stress conditioning unit. The output of the N4917A-E01/ -E03 drives the 81490A optical reference transmitter, which connects to the 81576A or N77-Series optical attenuator. The output of the optical attenuator connects to the device under test (DUT). The DUT electrical output connects to the J-BERT N4903B error detector input.

This closes the loop for BER measurement, which is the base for the highest level measurements of receiver sensitivity or jitter tolerance. If the DUT output is available only as optical signal, the conversion of the optical signal for electrical BER measurement can be performed with the help of the 81495A reference receiver, which can be added to the setup, but is not mandatory.

User Interface

The N4917A software runs on a PC with Windows® XP or Windows 7 (32 bit only). It controls the instrument setup over a USB to GPIB interface.

The user interface operates the instruments interactively, runs the compliance test automating various measurements (such as jitter tolerance) and controls the instrument’s setup and calibration. Interactive operation lets the user vary the optical parameters using dials. The automated measurements provide the generation of a report file.

Optimization, Adjustments and DUT Configuration

The setup to run the N4917A software with the necessary accessories is described in Figure 17. The N4917A automation and calibration software provides adjust­able parameters for ER, OMA, SI and PJ. At the standard compliance settings it displays the values for A0, VECP and the total jitter (TJ) according to the definition of IEEE802.3ae 2002 with help of an extrapolation from measured point gathered during a calibration process.

The software performs a cabling check, including an optimization for the phase matching of the differential data connection between N4903B data out and N4917A-E01 data in. This optimization is recommended the first time after setup, or whenever the cabling was removed. This cabling check is required for the 10GbE and 10GFC standards, for the 8GFC this check might be skipped by the user.

Beside the base points for the above parameters, it optimizes the operating point of the 81490A reference transmitter and it optimizes the crossing point of the optical signal for a minimum amount of duty cycle distortion (DCD).

The gathered information is stored in a file with reference to date and standard, which can be loaded any time later, multiple files can be generated, per default the latest is in use. Beside the optimization and the adjustments, the software stores in the second step the setup of the DUT.