Knowledge Base - FAQ

How to measure I-OSNR with Polarization Multiplexed signals

Tuesday, December 31, 2019
Submitted by ryan.grace on October 23, 2021 - 10:45pm
Question: 
How to measure I-OSNR with Polarization Multiplexed signals
Answer: 
40G and 100G Systems often use multiplexed polarization also called dual-polarization. Due to the modulation of both polarization directions it is challenging to extract the channel noise from the signal. No Polarization-nulling method is available today to calculate the noise figures caused by the polarization multiplex in service. The calculation of the OSNR without knowing all parameters of the measured system and method of polarization is not accurate enough.For dual-polarization signals we can just recommend to measure the Signal power first, shut down the signal to measure the noise power without signal with a bandwidth of 0.1nm. The calculation must be done manually. remark: This method is possible only if the ROADMs do not switch of the channel completely if the signal level gets too low. The JDSU OSA500R provides a procedure to support this manual OSNR test and calculation. 

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