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Simple, Intuitive Optical Spectrum Analysis

Jean-Sébastien Tassé

Product Manager

Jean-Sébastien Tassé has more than 13 years of experience in sales and marketing in the high-tech sector. He currently holds the position of Product Line Manager in EXFO’s optical business unit, where he oversees the business strategy, roadmap and launch strategy of the optical spectrum analyzer and dispersion product lines. At EXFO, he is also business development manager for the market segments of submarine networks and fronthaul/backhaul networks (optical products). He began his career as Sales Engineer for Gentec Electro-Optics, where he was responsible for direct and channel sales in specific regions in the Americas, Asia and Europe. As Business Development Manager for the Thin Film Research Laboratory at the École Polytechnique de Montréal/University of Montreal, he was instrumental in delivering revenue growth in analytical services for companies. Jean-Sébastien holds a bachelor's degree in Engineering Physics and a master’s degree in Electrical Engineering (optics) from Université Laval, in Québec City, Canada.

Hello! I will demonstrate you EXFO's Optical Spectrum Analyzer. I've got my OSA connected into the monitor port of an actual DWDM system, which has some 10 gig channels, 100 gig, and 200 gig channels. The easiest way to see what type of channels you dealing with is to use the button "Discover," so I hit the button "Discover," and the OSA will automatically scan all the spectral range, and show me the different wav lengths I've got present. Here I see I have seven channels. This, for instance, is a 200 gig channel, this is 100 gig, and these—channel 1, 3, 4 and 5—are all 10 gig channels. The trace is really power and dBM as a function of wavelength in nanometer. At the bottom, I've got all my channels, central wavelengths of each channel, power, OSNR value; we have to be careful because there's different types of channels, so we might have to use have to use in-band OSNR, Pol-Mux OSNR; so in this case, the noise level that we see here based on the OSNR method, is not the right one. One thing I noticed though, on this initial scan, is that one of the channels are not been properly defined. Now what I can do is, given I know I'm working on a 50 gigahertz grid, I can come here and put a 50 gigahertz channel width in my analysis set-up. I do "Okay," and then I push "Start." And I can make a new measurement, so I see all my channels are properly defined. Channel 1, 2, 3, 4, etc. Some of the interesting features of the OSA is the flexibilities in terms of displaying the graph, so I can for instance select the rectangle and I can zoom on a specific channel, like channel 1, like this for instance. I can also take the hand and move on my spectrum, to see my different channels. I can come back to full mode, like this. Then, if I come back here, I get access to my results. I have also access to what are called markers; so markers allow me to measure specific levels. If I'm interested in knowing, for instance, the distance between channel 1 and channel 2 in terms of nanometers, I can position my two markers like this: wavelenght Marker A, 1542.8 nanometers, Marker B, 1547.7 nanometers. Delta BA  in wavelength, that's 4.9 nanometers, or in power, I've got 16 dB of difference between the two, so the point taken here and this one. That's the markers. Okay. There are also different types of OSNR measurements we can make. We have the option here in the acquisition setting, so I have the in-band, and the i in-band. These two methods would be appropriate for 10 gig channels with networks containing ROADMs, or 40 gig non-coherent channels. Performing an in-band measurement is very simple; I just select i in-band, which is our new generation, and I just hit start, and wait for the OSA to perform the 500 scans. Now the in-band OSNR measurement is completed, so for all the channels that are not polarization multiplex, that is the 10 gig channels in this particular system, I see that I have, in terms of noise-type INB, the question marks tell me that these channels, the in-band OSNR analysis couldn't be made, and this is normal because these are 100 gig channel, or 200 gig, so channel 2, 6 and 7, we'll have to use another method. But for channels 1, 3, 4, 5, the in-band OSNR method has been applied successfully, and I get OSNR values around 27 dBs. Now I have my trace with all the seven channels on for the commissioning assistant. We'll save that trace. I save it on the desktop; I will call that trace "All On." I save it. That's it. Now we've just turned off channel 6, so we see that now we add the channel on; if I do another scan, we'll see that channel 6 is turned off. Now what I'm doing is, I'm doing in acquisition, in-band 100 scans of the system with channel 6 turned off. Now I have my trace for the commissioning assistant, channel 6 is turned off, 100 scans, so I will save it. I will bring up the keyboard, call it "Channel 6 Off." And I save it. Now channel 2, which is 100 gig, has been turned off. Now we'll make the acquisition for 100 scans of the whole trace, including channel 2 turned off. Now I have the trace for channel 2 turned off the commissioning assistant, so I will save that trace again. I bring up the keyboard here, we'll call it "Channel 2 Off." I save it, and now I can perform the commissioning assistant measurement, so I go in assistant, I choose commissioning. First step, some instructions, second step, select the trace with all channels turned on. I can load a measurement file, in this case I will go and select my trace "All On." Then, I go in Off channel traces; here I can select all that applicable traces with one channel turned off, I add my "Channel 2 Off," and I add my "Channel 6 Off." Last step: channel matching review. The OSA has associated to channel 2 and channel 6, the two traces with the channels off. I can decide the type of analysis I want, either the CCSA, the standard from China, or the IEC standard. I will choose the IEC standard, the newer one, and I hit "Okay." Then I get my OSNR results, here for channel 2, and channel 6, based on the IEC standard.