Testing With Real-World Conditions

The Circadiant family of Optical Standards Testers (OST) are 10 gigabit/second optical bit error rate testers (BERT) with the unique ability to simulate real world conditions by varying the optical power, extinction ratio, jitter, rise/fall time, and Optical Signal to Noise Ratio of the optical signal.

Parametric Real World Testing

Old Methods For Testing Receiver Sensitivity

In the past, receiver sensitivity has always been measured by reducing power until bit errors of a given level are detected. Reducing the power only simulates one real world degradation; extinction ratio, jitter, noise level and rise/fall times can have a more dramatic effects on the network, which are not taken into account using old methods: 

Circadiant Method for Testing Receiver Sensitivity

The Circadiant OST sweeps the power of the optical signal to automatically create Power vs Bit Error Ratio plots which indicate the true module or network performance over a full range of power. We then take it a few steps further and allow you to modify the optical eye by adjusting the extinction ratio, jitter, rise/fall time, and OSNR of the signal. These optical degradations have a dramatic effect on the receiver sensitivity.

Optical Degradations and their Effect on Receiver Sensitivity.

Receiver sensitivity is affected by many parameters; varying optical power alone is not a true test of a receiver’s performance. A receiver that demonstrates great performance under ideal conditions could prove to be terrible under real world (stressed) conditions. Unfortunately there is no correlation between a receiver’s sensitivity when tested with a perfect signal versus a real world or stressed signal. To ensure true real world performance a receiver must be tested with real world conditions.

Standards Require Real World Signal Testing

Due to the change in lower cost optics and the need to maintain a plug-and-play architecture standards have begun to require real world signal testing.  Standards guarantee a plug-and-play network but only if everyone is compliant.  The only way to ensure compliance is to test with the true real world conditions. 

Ethernet and Fibre channel have led the way in real world signal testing.  The following standards all require physical layer testing using degraded signals to simulate real world conditions and ensure a plug-and-play architecture.

• 1GE IEEE 802.3
  
• 10GE IEEE 802.3ae SR to LR interfaces  Section 52
  
• 10GE IEEE 802.3aq   LRM interface  Section 68
  
• 10FC IEEE