After the optical module is installed, testing its performance is an essential step.When the optical components in the entire network system are supplied by the same vendor, if the network system can work normally, there is no need to separately test the sub-components of the system.However, most of the sub-components in most network systems are from different vendors. Therefore, testing the optical components, especially the performance and interoperability of each optical module is crucial. So how do you test the performance of an optical module?
The optical module is composed of a transmitter and a receiver.When the transmitter is connected to the receiver through the optical fiber, if the error rate of the entire system does not achieve the expected effect, is it a transmitter problem or a receiver problem? The test optical module is generally divided into four steps, which are mainly divided into tests for the transmitter and the receiver.
Transmitter test
When testing, you need to pay attention to the wavelength and shape of the transmitter output waveform, as well as the jitter tolerance and bandwidth of the receiver. When testing the transmitter, you need to pay attention to the following two points: First:The quality of the input signal used to test the transmitter must be good enough.In addition, the quality of the electrical measurements must be confirmed by jitter measurements and eye diagram measurements.Eye diagram measurements are a common method of checking the output waveform of a transmitter because the eye diagram contains a wealth of information that reflects the overall performance of the transmitter.
Second:The output optical signal of the transmitter must be measured by optical quality indicators such as eye diagram test, optical modulation amplitude and extinction ratio.
Receiver test
When testing the receiver, you also need to pay attention to the following two points:
First:Unlike the test transmitter, the quality of the optical signal must be sufficiently poor when testing the receiver. Therefore, a light pressure eye diagram representing the worst signal must be created. This worst optical signal must pass the jitter. Measurement and optical power tests are used for calibration.
Second:Finally, you need to test the receiver’s electronic output signal. There are three main types of tests:
Eye diagram test: This ensures that the “eyes” of the eye diagram are open. Eye diagram testing is usually achieved by the depth of the bit error rate
Jitter test: test different types of jitter
Jitter tracking and tolerance: Test the tracking of jitter by the internal clock recovery circuit
The light test module is a complicated task, but it is also an indispensable step to ensure its performance. As a widely used measurement method, eye diagram measurement can effectively test the emitter of an optical module. The receiver test of the optical module is more complicated and requires more test methods.