4 Ways to Test the Speed of Transceivers

Keith AndrewsPresident
More and more people are using the enhanced small form-factor pluggable (SFP+) tranceivers, and speed is of utmost importance. Testing of speeds are critical to ensure that the devices will meet the speed requirements. There are some testing challenges, but once you overcome those hurdles, you’ll be on your way to learning more about the speed of the transceivers. 

Here are some of the challenges you can expect when testing the speeds of transceivers and also some of the recommended ways to test the speed of any transceiver. Armed with this information, you should be able to achieve desired transceiver performance. 

1. Analog Transceiver Testing 
Analog transceiver testing requires a baseband signal that originates at the Radio Frequency tester and is provided to an analog transceiver. Usually, the DAC providing the signal is located internally. Parallel or serial digital input/output signals are commonly used, and these signals will be provided and acquired by the tester. The device will up-convert the baseband modulated signal to an Radio Frequency frequency. This type of transceiver will usually require a reference clock. A tester would acquire the signal, demodulate the signal, and test the parameters. 

2. Radio Frequency Tester Increasing Demands
Radio Frequency testers are growing in demand. They evolved from the analog signal analyzers and have grown to use digital modulation techniques. Third-order intercept, harmonic distortion, and compression have all changed to meet the wider range of IF bandwidth requirements. Radio Frequency testing is one of the more accurate tests because of the accuracy of digital modulation. 

3. Linearity Tests 
In addition to Radio Frequency testers, linearity tests require the wider IF bandwidth. Two tests that are commonly used are the adjacent channel power ratio (ACPR) and the output spectral mask testing. These tests are now used to measure speed in LAN devices and 3G cellular devices. Low noise floor and phase noise are two of the problems that linear tests look for that may affect speed and performance. 

4. TWDPc Measurement 
TWDPc measurement must be mastered. A special algorithm is required to ensure that the proper tests are established. This test is defined differently and must be specified to get an accurate measurement. For instance, this test is “defined as a measure of the deterministic dispersion penalty due to a particular transmitter with reference to the emulated multi-mode fibers and a well-characterized receiver.”

SFP+ Testing Challenges 
These four tests are just a few that are used to test speed and performance, but there are many others that are used. Keep in mind that there may be numerous challenges related to testing speed and performance. One of the most common challenges is the “ SFI between the host board and the SFP+ module.”

Each of the tests may have a different number of measurements required. The time the test takes may be anywhere between three minutes and one hour. During the testing phase, it’s difficult to “move seamlessly from a compliance environment to a debugging environment.” It’s important to know the challenges to ensure that you get an accurate speed reported.

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